Ajax

HDPE water tank repair

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The bung for the foot pump connection on my stbd water tank has cracked and I lost 30 gallons of water. I'm currently operating off of the bow tank so I still have 30 gallons.

There is a company, Maritime Plastics in Annapolis that might be able to repair it if I can contact them which is Plan A. I never stop there, I'm already working on Plans B, C and D.

Plan Z is a Plastimo 30-ish gallon bladder. I am not enamored with this prospect. Bladders always leak no matter how hard the manufacturers brag on their construction. Plan C or D is to buy a plastics welding kit from Harbor Freight and attempt to weld the fitting myself. The main problem with this is my lack of experience. I need to know the proper melting temperatures for the thickness and type of plastic, for example.

I'm trying to avoid buying an entire new tank, but I'll go down that road if I have to.

Any advice and recommendations are appreciated.

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Does the tank have a cleanout/access hatch that would allow you to get at the area where the 'bung' is located? If so, you could cut out the damaged bung and install a thru-hull or or similar threaded adaptor. Plastic welding is your best bet, but hot melt glue might get you through for a while...

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You could have the plastics company spin-weld in a new, larger fitting if the crack is not fixable.

Or, you might be able to fix it with G-Flex.

Or, you could rent a Steinel heat gun and buy some HDPE welding sticks. It's not rocket surgery.

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If possible, patch the crack; drill a new hole & install a new fitting. 

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2 hours ago, Ishmael said:

You could have the plastics company spin-weld in a new, larger fitting if the crack is not fixable.

Or, you might be able to fix it with G-Flex.

Or, you could rent a Steinel heat gun and buy some HDPE welding sticks. It's not rocket surgery.

This is a case where I don't think I want to patch with any kind of goop. I'm afraid it won't stand up to the range of temperatures we experience here and also any strain on the fitting (yeah I know, there shouldn't be any lateral strain once everything is connected).

I've done a heap of Googling and there aren't many plastics *repair* companies within driving distance. Lots of people making plastic stuff locally...but not water tanks and not repairing. There's the place in Annapolis and another place near Arlington, Virginia. That would be an annoying drive but I'd do it if that's what it takes.

I'm damn tempted to weld it myself. It wouldn't be the first time I've taken on an entirely new skill with zero experience. There's gotta be a Youtube video on this...

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We had a custom plastic water tank welded up by a normal fabrication shop at a shipyard once - they normally did metal welding, but had the tools and expertise to do plastics as well even though not advertised as such - if you have any good shops closer than Annapolis.

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Check into RV repair shops, they do a lot of plastic tank repairs.

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I used G-flex to repair the threaded bottom pickup of a HDPE water tank. It would sometimes have a head of 5' of water. Lasted for years. So I think in this case G-flex is a very good repair choice.

If you have an inspection port you can add a barbed thru-hull with a rubber gasket inside the tank (the mushroom head in the tank, hose barb on the outside of the tank)

You can easily add an inspection port and seal with silicone for aquariums (non toxic to fishes so I think OK for humans too)

 

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5 minutes ago, Zonker said:

I used G-flex to repair the threaded bottom pickup of a HDPE water tank. It would sometimes have a head of 5' of water. Lasted for years. So I think in this case G-flex is a very good repair choice.

If you have an inspection port you can add a barbed thru-hull with a rubber gasket inside the tank (the mushroom head in the tank, hose barb on the outside of the tank)

You can easily add an inspection port and seal with silicone for aquariums (non toxic to fishes so I think OK for humans too)

 

Or just add a screw in dinghy inspection port, they seal up OK and it’s only water...

 

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  Plastics have whats termed a 'low energy' surface and don't make molecular bonds very well.  Epoxy adhesion to PE is poor unless you first caramelize the surface with a flame.

Anyone local who can fix Plastic kayaks could plastic weld it for you.

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Try Marine Goop.  I "temporarily fixed a similar issue on the water tank of my  previous boat.  Twelve years later, when I sold it you couldn't tell it had ever been fixed 

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G/Flex did real well on a PVC repair, and be sure to follow the directions which include flame treatment. I’d go with G/Flex, if I were you

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Yeah the flame treatment is actually very subtle. NO carmel color, blackening or anything just a quick brush back and forth with a propane torch. 

I've used G/flex to glue UHMW anti chafe blocks / deflectors on the deck.They had a very highly loaded genoa sheet rubbing on them to get the winch lead just right. Never budged.

Nothing used to easily glue UHMW. This stuff works

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9 hours ago, Ajax said:

The bung for the foot pump connection on my stbd water tank has cracked [...]

Any advice and recommendations are appreciated.

If the crack is on the bung itself, that is, on the tapered threads, no repair will hold for a reasonable length of time because of the stress.  What you would do in that case is cut out the bung and the crack and close up the area with new plastic sheet, either welded, attached with adhesive, or mechanically fastened.  You can use a larger bung and reduce the fitting outside the tank, if there is room, which will allow you to cut away the existing fitting's skirt.

If the crack is on the tank wall where the bung attaches, there is the possibility of repair, either by welding, or with G/flex, or with epoxy and fiberglass using the flame technique mentioned upthread.  I've tried all of these with, at best, mixed results.  I got a weld to stick on some hydroponic tanks once, after a few tries, and failed in various other endeavors.  G/flex is IMO your best bet, still use the flame, not enough to color just a 1" per second pass with a torch.  Generally you would want to be epoxying a piece of HDPE over the crack so as to create maximum surface area for adhesion, rather than trying to repair the crack itself.

The problem with stress cracks in older HDPE is that they usually indicate that the material has lost its plasticity.  Even a careful repair can fail, or lead to new cracks near the repair where there is now a concentration of stress.

My first piece of advice would be to go through the plastic-mart.com web site and see if you can find something that will fit your space.  I've used them before and they're good.  Replacing the tank with something that is reasonably close in size is going to be your very best bet for minimum hassle and cost.  Who knows, you may be able to shoehorn in a bigger tank, if not, well, maybe add another tank somewhere if you really need the capacity.  Don't limit yourself to marine tanks, look at their RV stuff etc also.

They also have mechanically-attached bungs (with gaskets) and you could maybe cut out your existing bung and the crack and use one of those if you can't find something that will fit.

You could also look at ABS tanks.  They are much easier to modify or repair as they can be solvent welded with good results.  I believe some are considered suitable for drinking water.  It has been my experience that they last longer.

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HTPE is pretty forgiving, it is simply fuse welded.  Hot plate put the pipes together simple.  The water reactive rescue tape bonds fairly well to it.  Used to use it in production plant water lines quite a bit.  It's popular with the Danes.  You may be able to weld cap and add a mechanical fitting somewhere else.  I added a couple schedule 80 PVC fittings to our blackwater tank, just need a way to get your hand in to install.  Something like a foot pump doesn't need to be at the bottom and could easily be changed to a top suction with down pipe if need be.

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Of course the tank part number is illegible. 

The tank is glued to the hull with foam. So much winning. 

20200914_165202.jpg

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Are you kidding me?

1. You've got a label.

2. You've got a serial number.

3. The company is still in business.

You hit the trifecta!

If you were expecting more than that, well, you've got some boat lernin to do...

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What good is a nearly blank label? I just learned that Kracor was sold to Yamaha and they took down their online catalog. 

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Call them up with the approximate tank dimensions and the serial number to see if they can help you out with repair advice, a line on a replacement, whatever. Can't hurt.

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42 minutes ago, Ishmael said:

I just got back from the boat. I still haven't broken loose all the foam but I'm making progress. Some kind soul wrote the number in magic marker on the end of the tank. It matches the faint numbers on the label. Combined with the .pdf you just provided, I'm in business.

It's 1-5071, 36 gallons.

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Not very difficult to weld with the proper hot air gun. Practice a bit on some scrap first. I'd try that before the flaming and G-Flex, but that will work too. 

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1 hour ago, DDW said:

Not very difficult to weld with the proper hot air gun. Practice a bit on some scrap first. I'd try that before the flaming and G-Flex, but that will work too. 

Back to renting a Steinel, if you can. There are apparently some better, but not priced for mortals.

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This will probably do it. Certainly cheaper than a new tank, or even a long drive somewhere. Being a fine example of HF tools, it will probably last through at least one or two repairs :).

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I just got the tank out of the boat. 3 of 4 fittings are damaged. One was a total hack job of a white, plastic thru-hull and gobs and gobs of sealant. Oddly, that fitting wasn't leaking!

It's obvious that someone forgot to drain and winterize. Why else would the VENT fitting at the top of the tank have a crack?  The vent fitting and foot pump fittings are just hair line cracks on the spin welded bungs.  I'm not sure what's the best approach- fill with G-Flex or try to heat weld some HDPE into the crack.

The main fitting for the electric pump is royally hosed. The bung was essentially cut off. The hole is now oblong and ruined. I'm calling RV shops now...

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Are you still trying to repair? Or replace ? Check out 'Ardemco.com" for a whole lot of plastic tanks

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18 minutes ago, longy said:

Are you still trying to repair? Or replace ? Check out 'Ardemco.com" for a whole lot of plastic tanks

Ok, RV places say no. Ardemco doesn't keep their funky shaped tanks in their online catalog. I called, and spoke to a gentleman. I emailed him the Kracor catalog along with my tank's mold number. He'll look in their inventory to see if they have anything compatible.

I did speak to Kracor today. They confirmed that they won't sell direct to me, only through Tartan. I called Tartan, couldn't reach a human being, so I left a voicemail with parts and aftermarket support. My guess is that since I'm not buying a new yacht, they'll tell me to pound sand.

Maritime Plastics in Annapolis could fix this tank completely but the guy simply doesn't answer his phone or return calls. I'm going to throw the tank in my car and drive down there. It's not that far.

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There is a place in RI, my friend had all fuel and water for his boat done with them, I can't remember the name, but I think they do alot of large truck tank for fire rigs etc.

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2 hours ago, Ajax said:

Ok, RV places say no. Ardemco doesn't keep their funky shaped tanks in their online catalog. I called, and spoke to a gentleman. I emailed him the Kracor catalog along with my tank's mold number. He'll look in their inventory to see if they have anything compatible.

I did speak to Kracor today. They confirmed that they won't sell direct to me, only through Tartan. I called Tartan, couldn't reach a human being, so I left a voicemail with parts and aftermarket support. My guess is that since I'm not buying a new yacht, they'll tell me to pound sand.

Maritime Plastics in Annapolis could fix this tank completely but the guy simply doesn't answer his phone or return calls. I'm going to throw the tank in my car and drive down there. It's not that far.

At the time I was doing this, it was the same price to have one built locally as to have one shipped in, especially since Kracor didn't stock it and would have had to make the tank from scratch, and charged a $200 setup fee. The catalogue was very handy as a source of measurements for my bow tank, with custom fitting locations.

MVlPXFW.jpg

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Have you looked at marinesan.com to see what tanks they have that might fit?

https://marinesan.com/holding-tanks-for-sewage-water/

The lists are in links at the top.  They'll customize the fitting location too (the tanks are whole with no fittings in their warehouse, and then spin weld the fittings on site).  Hopefully there is a similar service with good stock in Annapolis too.

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You could try Ronco plastics (ronco-plastics.com). They have a big range of tanks, and  great on-line catalog with sketches & dimensions.

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Ok, great news:

Although they were unresponsive to phone calls, I threw the tank in my car and drove to Annapolis Maritime Plastics. I half expected to find them shuttered due to COVID but the doors were open and they were quite busy. A very chill, polite gentleman came out, looked at the tank, nodded and went back inside to check if they had the fittings that were on my tank.

3 minutes later, the guy walks out with the fittings in his hand. He writes my name and phone number on the tank and says "2-3 days."  He said he'll cut off all the old fittings and spin weld brand-new fittings on. When I asked about the bodged up fitting, he said it wasn't a problem at all.

Scrawled on a scrap piece of plastic above the service desk- "Attention Sailors-  On the ocean, the wind may be free but here it costs $120 an hour."

I don't care if they charge me $200 to weld those fittings, I'll still be way ahead of the game financially and in my precious personal time.

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Ardemco got back to me with a slightly smaller, but otherwise identical tank. I'll lose a few gallons of capacity but it would be a drop-in solution. This is just "Plan B" in case Maritime Plastics fails to come through with the repairs.

Let's talk re-installation:  The original tank was plopped into wet, expanding foam. When the foam dried, it adhered to the tank. The actual bond to the slick, plastic surface wasn't that great but the sheer amount of surface area held the tank in place quite strongly. The tank was very difficult to break free. A wood grid was then placed over the tank and secured with screws and tabbed directly to the hull.

Now I've broken that bond to the foam. The foam is still in place and will cradle the tank perfectly so I don't want to scrape it all out.  What can I slather on the foam base that will adhere the tank to the foam again? Would epoxy eat the foam? Damage the tank plastic?

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Not sure you need to bond it again.  Especially if the foam keeps it from moving around.  And the hold down straps (wood grid) should keep it locked in place.  

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30 gallons x 8 lb/gal = 240 lb. That's a lot of weight trying to bounce around in sporty conditions. How stout is the wooden grid and fastenings? Any before pics?

Yoyo might be right but a a belt and suspenders approach would be to get a can of expanding foam to apply to the old foam in a spotted grid over the tank's footprint before you set the tank in. The new foam will adhere well to the old and mimic the original bond to the tank. I wouldn't want to use too much expanding foam, you want to give it enough room to expand laterally and into the old stuff, not actually lift the tank. I'd score some expansion grooves in the old foam beforehand between the position of the blobs of new foam to give it somewhere to go. By the same token, I'd fill the tank immediately after setting it in place to weigh it down and fasten the wood back down. 

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1 hour ago, IStream said:

30 gallons x 8 lb/gal = 240 lb. That's a lot of weight trying to bounce around in sporty conditions. How stout is the wooden grid and fastenings? Any before pics?

Yoyo might be right but a a belt and suspenders approach would be to get a can of expanding foam to apply to the old foam in a spotted grid over the tank's footprint before you set the tank in. The new foam will adhere well to the old and mimic the original bond to the tank. I wouldn't want to use too much expanding foam, you want to give it enough room to expand laterally and into the old stuff, not actually lift the tank. I'd score some expansion grooves in the old foam beforehand between the position of the blobs of new foam to give it somewhere to go. By the same token, I'd fill the tank immediately after setting it in place to weigh it down and fasten the wood back down. 

Eh, the wood grid is pretty solid but I found 2 of the 3 hull  tabs broken. They were pretty pitiful tabs, though. Mine will be better.

I like your idea of just adding a bit of expanding foam to re-bond to the old foam and the tank. Cutting grooves also sounds like a sound idea. If the stuff comes in a spray can as opposed to some sort of binary mix, that would be great.

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This stuff looks like it'll work well enough:  https://www.homedepot.com/p/GREAT-STUFF-PRO-26-5-oz-Wall-and-Floor-Adhesive-343087/202892488

(foam + adhesive)

Like I said, the original foam did not adhere well to the plastic tank. The stuff scraped right off by hand. The bond was tenacious due solely to the large surface area.  This Great Stuff construction adhesive is probably really meant to bond with wood and concrete, but I think it will achieve the same effect.

Losing this tank cut my water capacity in half during my vacation. It wouldn't be such an annoyance if the bay water were clean enough to wash dishes but it's way too turbid in the middle bay. Plus, we have nettles so thick that I'd probably be washing my dishes with them!

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As others said I would think that spray foam would work well.  It is sticky but not real strong.  But should work with all the surface area.  The product you linked was not foam.  It would not fill any spaces and may not be compatible with the foam already there.  

 

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1 hour ago, Ajax said:

This stuff looks like it'll work well enough:  https://www.homedepot.com/p/GREAT-STUFF-PRO-26-5-oz-Wall-and-Floor-Adhesive-343087/202892488

(foam + adhesive)

Like I said, the original foam did not adhere well to the plastic tank. The stuff scraped right off by hand. The bond was tenacious due solely to the large surface area.  This Great Stuff construction adhesive is probably really meant to bond with wood and concrete, but I think it will achieve the same effect.

Losing this tank cut my water capacity in half during my vacation. It wouldn't be such an annoyance if the bay water were clean enough to wash dishes but it's way too turbid in the middle bay. Plus, we have nettles so thick that I'd probably be washing my dishes with them!

I'd try to clean the tank off as best you can, sand it to give it some tooth, flame treat to activate the plastic surface, and then foam her in. 

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An opposing opinion: I would not glue it in. Tanks are a serviceable item as you have experienced. Make the strapping tough enough to hold it. 

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25 minutes ago, DDW said:

An opposing opinion: I would not glue it in. Tanks are a serviceable item as you have experienced. Make the strapping tough enough to hold it. 

I agree.  Especially if you re-install the old tank.  I would assume that the parent material of that tank is in it's last stretch, and that you may end up replacing it sooner rather than later.  Why make that a harder task than necessary.

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13 minutes ago, DDW said:

An opposing opinion: I would not glue it in. Tanks are a serviceable item as you have experienced. Make the strapping tough enough to hold it. 

I can just scrape the foam off to break the bond the same way I did this time. This thing is a several hundred pound missile if it ever gets free.

@Expat Canuck Why is the parent material on its last legs? It was never exposed to UV or anything besides water and pink RV anti-freeze. The fittings had hair line cracks indicative of freeze damage, not materials failure.

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If the can straps breaks and it can come loose, a bit of Home Depot spray foam isn't the solution - better straps are. But that is just me talking, I overbuild everything. "Overkill is underrated". 

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1 minute ago, DDW said:

If the can straps breaks and it can come loose, a bit of Home Depot spray foam isn't the solution - better straps are. But that is just me talking, I overbuild everything. "Overkill is underrated". 

You're not wrong. I was always going to beef up the tabbing. The grid itself seems pretty strong.

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I think the main benefit of the foam is to keep the tank from working but as long as you're using it, you might as well try to get it to stick well. 

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My water tank under my port settee is held in place by the seat framework above it, not glued in.  I'm happy with that, it allowed me to pull the tank and clean it by pouring a bunch of javex in and rolling it around on a dock to spread it about.  I wouldn't glue it back in, I'd beef up the retaining system.

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6 hours ago, DDW said:

If the can straps breaks and it can come loose, a bit of Home Depot spray foam isn't the solution - better straps are. But that is just me talking, I overbuild everything. "Overkill is underrated". 

This.

Treat the foam as a cradle and make sure the straps are capable of taking the load. That's how my tanks are fitted and I built it for myself so it's not cheaped out.

Tanks are things that need to be removable unless they're part of the actual boat structure.

FKT

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Yesssssss. My tank is ready. 

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Cheeze and rice, what a hassle.

I bought new, screw-in hose fittings. I think they're cheap crap. I couldn't get one of them to seal up so I just went back to the old gray, PVC screw-in fitting and a generous application of teflon tape.

I accidentally splashed a bunch of water around, which made it 2X more difficult to verify that nothing was leaking.

Then, the water pump began cycling periodically. I thought "what could this have to do with the tank replacement? The tank is on the low pressure side!"  I chased all over the damn cabin for 2 hours, searching for a leak on the pressurized side. Nothing. Dry. Faulty pressure switch? Nope,  I had a loose hose clamp on the water heater in the engine space, quietly spewing water everywhere.

I finally got everything dry, bilge pumped out, stray water vacuumed out or toweled up. The tank has about 7 gallons in it and I'll make one final leak check this afternoon before tabbing the hold-down grid to the hull and buttoning everything back up.

I need a hug. :(

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1 hour ago, Ajax said:

Cheeze and rice, what a hassle...I need a hug. :(

OO - hugs to ya Ajax.

A thread sealing compound such as Swak or Loctite Thread Sealant with PTFE is your friend when it comes to plastic plumbing. I subscribe to the belt and braces approach, first wrapping the male thread with Teflon tape and then doping it with sealing compound. The compound stays flexible and the fitting does not need a lot of torque to seal properly.

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1 minute ago, Jim in Halifax said:

OO - hugs to ya Ajax.

A thread sealing compound such as Swak or Loctite Thread Sealant with PTFE is your friend when it comes to plastic plumbing. I subscribe to the belt and braces approach, first wrapping the male thread with Teflon tape and then doping it with sealing compound. The compound stays flexible and the fitting does not need a lot of torque to seal properly.

I should have realized that thread sealants have come a long way. The original manual for my tank says not to use ANYTHING other than PTFE tape. Sometimes I get a little too literal for my own good.

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Wouldn't you want to fill the tank to the top, even up to the deck-fill fitting, for a few days, run the pump a bit, before tabbing it all in?

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1 hour ago, eric1207 said:

Wouldn't you want to fill the tank to the top, even up to the deck-fill fitting, for a few days, run the pump a bit, before tabbing it all in?

I've run the pump. Yeah, I'll fill it up to the top before tabbing it. The only thing at the top is the vent fitting, which should be checked.

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Filling it up will also static test the lower fittings, though I hope the shop pressure tested the tank before giving it back to you.

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4 minutes ago, IStream said:

Filling it up will also static test the lower fittings, though I hope the shop pressure tested the tank before giving it back to you.

They are not equipped for that. They're a plastics shop, not a tank repair shop. I knew this going in.

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Nothing an air compressor and a Schrader valve can't fix! :ph34r:

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Re foaming:  If you decide to go this route, suggest considering the "low expansion" stuff for window frames.  Other stuff can really create a LOT of pressure.

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16 minutes ago, IStream said:

Nothing an air compressor and a Schrader valve can't fix! :ph34r:

Just curious- when performing a test like this on a tank not meant to hold "pressure", how much pressure would you apply? 1-2 psi?

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A water tank 2.32 feet deep will have a pressure at the bottom of 1 psi. So, yeah, around 2 psi would be prudent. A dinghy is from 3 to 4 when firm. For example. Cruiser dinghies less than 1...heh.

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A column of water 10" tall exerts 0.36psi on the floor of the tank, so I'd probably go with that factored to the actual height of the tank then multiply by ~3 to account for dynamic pressure when in rough seas. 

You can make a pressurizing adapter by cutting the valve out of a bicycle innertube, leaving a generous flange of rubber at the base, then drill a hole through a PVC cap, pass the valve through the hole from the inside, and glue the valve to the cap using the flange to increase the bonding area. 

For safety, I'd fill the tank with water and only pressurize a small volume of air in the tank.

Or you can just blow into the vent fitting and hold it for a minute. Most people can blow a bit more than 1 psi.

Or you can just fill the tank fully up and call it good on the assumption that if the fittings don't leak at ~0.5psi, they won't leak at ~1.5psi. 

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1 hour ago, IStream said:

Nothing an air compressor and a Schrader valve can't fix! :ph34r:

I would not use a air compressor unless you have a very good way to reduce the pressure.  Good way to go to high quick and blow something.  Do it slow with a hand pump 

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In industry, hydrostatic tests are required up to the height of the vent.  So, you fill until it overflows at the vent.

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18 minutes ago, seaker said:

I would not use a air compressor unless you have a very good way to reduce the pressure.  Good way to go to high quick and blow something.  Do it slow with a hand pump 

Agreed, that's why the ninja!

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37 minutes ago, Expat Canuck said:

In industry, hydrostatic tests are required up to the height of the vent.  So, you fill until it overflows at the vent.

This - if it doesn't leak with a full head of water on it, then it's unlikely to leak when you have much less pressure (which is as soon as you use enough water to empty the fill and vent hoses).

Plus, if it does leak, water is more obvious than leaking air, and, on a boat, easy to deal with.

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8 hours ago, Ajax said:

I should have realized that thread sealants have come a long way. The original manual for my tank says not to use ANYTHING other than PTFE tape. Sometimes I get a little too literal for my own good.

Loctite 5331 for plastic pipes or plastic to metal. Loctite 567 for metal pipes. There's something in 567 that plastic doesn't like.

I haven't used teflon tape in years and if I have my way I never will again. This stuff always works and you can always get fittings to 'clock' where you want them to without hassles.

FKT

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@Fah Kiew Tu I'm not taking the tank apart now, but I will buy some 5331 and keep it on hand.

The tank is full, the voids and bilges are bone-dry. I'm calling it good and I'm putting everything back together.  I appreciate all the advice on this topic. I've had some frustrating breakages this season but better now than in Maine or somewhere in between. COVID may have done me a small favor.

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On 9/21/2020 at 5:54 AM, Ajax said:

I should have realized that thread sealants have come a long way. The original manual for my tank says not to use ANYTHING other than PTFE tape. Sometimes I get a little too literal for my own good.

I know you have yours back together already. But i wanted to put out the warning to check sealent paste labels to ensure insure compatiblity with your material. I have seen in the pool industry many times where pvc and other plastics have become softened from the paste. Some sealents are made only for metal (gas) pipe. Since I dont work with it on a regular basis any longer I always check the label every time I use any paste.

Personally i have never found a need to use tape and paste. Never tried it.  Usually find that less is more when sealing almost anything - sealent or torque. 

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On 9/21/2020 at 1:11 PM, IStream said:

For safety, I'd fill the tank with water and only pressurize a small volume of air in the tank.

^^^^ This.

Do not, I repeat, DO NOT fill up a non-pressure rated tank with pressurized air for a leak test. Even if it is "only" 1 or 2 psi. The force exherted by a 2 psi pressure on a 3ft x 2 ft panel is 1,700 lbs force. Think about it.

If it is 95% filled with water and 5% pressurized air, a catastrophic failure will go: PFFITTT

If it is full 100% of pressurized air, it is what we call in my industry an "energized fluid". Any failure will go:

KAH-BOOOM !!!

Don't ask me how I know...

 

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Alrighty then!

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On 9/21/2020 at 11:27 AM, Expat Canuck said:

In industry, hydrostatic tests are required up to the height of the vent.  So, you fill until it overflows at the vent.

Yes. Do this. Hook up a hose about equal to your vent height and fill it till it's at the top.

DO NOT use air. Way too risky.  Unless you have a pressure gauge you really trust.

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On 9/21/2020 at 4:22 PM, Fah Kiew Tu said:

Loctite 5331 for plastic pipes or plastic to metal. Loctite 567 for metal pipes. There's something in 567 that plastic doesn't like.

I haven't used teflon tape in years and if I have my way I never will again. This stuff always works and you can always get fittings to 'clock' where you want them to without hassles.

FKT

I used to be pretty anti tape outside of anti gauling but have come full circle with plastics.  When I installed our spectra watermaker it's all plastic and they had pretty specific instructions for fitting threads.  Made a believer out of me.  For plastic now I use heavy tape alone and 6-8 wraps, have not had any issues since.  Metal fittings and various mediums etc completely different story but for plastic I only use tape now.

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38 minutes ago, Zonker said:

Yes. Do this. Hook up a hose about equal to your vent height and fill it till it's at the top.

DO NOT use air. Way too risky.  Unless you have a pressure gauge you really trust.

I actually already did it this way.  My tank vent has a fitting with a hose. 

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1 hour ago, SASSAFRASS said:

I used to be pretty anti tape outside of anti gauling but have come full circle with plastics.  When I installed our spectra watermaker it's all plastic and they had pretty specific instructions for fitting threads.  Made a believer out of me.  For plastic now I use heavy tape alone and 6-8 wraps, have not had any issues since.  Metal fittings and various mediums etc completely different story but for plastic I only use tape now.

I'm not saying don't use tape, just offering up the Loctite products as alternatives. Personally I no longer use tape but that's my choice and as everything to do with engineering/fitting, subject to change as circumstances or knowledge changes.

The 5331 works really well though.

FKT

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11 hours ago, Fah Kiew Tu said:

I'm not saying don't use tape, just offering up the Loctite products as alternatives. Personally I no longer use tape but that's my choice and as everything to do with engineering/fitting, subject to change as circumstances or knowledge changes.

The 5331 works really well though.

FKT

I meant to ask- is the 5331 food grade/food safe?

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If you Google MSDS, material safety data sheet, for anything it will give you all food safety info.  This one is not food safe.  They have a range of food safe 2046, 243, 262.  But I don't think anything that is the same.  I wouldn't worry about it unless you are using one tube per fitting.

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17 hours ago, SASSAFRASS said:

I used to be pretty anti tape outside of anti gauling but have come full circle with plastics.  When I installed our spectra watermaker it's all plastic and they had pretty specific instructions for fitting threads.  Made a believer out of me.  For plastic now I use heavy tape alone and 6-8 wraps, have not had any issues since.  Metal fittings and various mediums etc completely different story but for plastic I only use tape now.

When I installed my Spectra, it was done with teflon tape. Leaks everywhere. After disassembly and reassembly twice with tape and once with sealant, in frustration I did what Spectra told me as the backup plan. Put it together with 5200 :blink:. Hasn't leaked since. 

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7 hours ago, DDW said:

When I installed my Spectra, it was done with teflon tape. Leaks everywhere. After disassembly and reassembly twice with tape and once with sealant, in frustration I did what Spectra told me as the backup plan. Put it together with 5200 :blink:. Hasn't leaked since. 

Sikaflex 291 works really well too.

Best used just before you sell the boat, though.

FKT

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