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Update: went with the Jabsco V-Flo 5.0. It is variable speed/flow and does not need an accumulator. Price was great at Defender. Thanks for all the input!
Not sure it's a real problem but when you turn the tap off the PID isn't going to help much, is it? I'd expect there to be a pressure spike. I've got one of those tiny Whale surge dampers in my system. I haven't tested it without but it seems like a good idea. IIRC, it was called for in the documentation.With a decent PID built into the logic and some sort of hysterisis you don't need a accumulator. It's going to come on spool up slow to meet pressure and have a differential to eliminate short cycling.
TLDR version: I've got no pressure drop issues but it's probably because even without a dedicated accumulator, there's so much compliance in my water lines that I'm effectively still running with an accumulator. Before removing the dedicated accumulator, I found that priming usually worked but not always. I need to re-test this now that the accumulator is out and think it'll be more reliable.IStream, how much delay do you get when turning on a tap? And where is your pump in relation to the tank?
This is only annoying to me when taking a shower, as I have the trigger shower head. Pull the trigger and there is a momentary droop in pressure. It has varied a bit and seem to do with any air in the suction side, and also the water level in the tank. I have had trouble with suction leaks on that side.
I put a Sea Tech / Watts quick connect fitting on the input to my pump to facilitate servicing and it seems to be airtight in suction, at least for now. Everything upstream from there to the tanks is barbs and clamps. @El Borracho I agree that it would be great to have a gravity prime but it's just not practical with my tank arrangement.Well you have confirmed by suspicion that the suction side has to be truly vacuum tight. Even the typical Whale shark-bite type quick connects aren't vacuum rated. I think the accumulator probably contributes to the priming issues because it can develop very little pressure when dry, and has to push that through the internal check valve. If it also has to do that against pressure in the accumulator it can't make matters easier. I cannot get it to prime into a shut system, I have to open a tap while I prime. Once the gears get a little wet it takes off. A solution I've thought about is to put a barb fitting in place of the priming screw, tube on it running to a convenient location where a valve could be cracked. The automated version of this is a tube or fitting with a restrictor allowing only a tiny bit of water through (but a lot of air) that returns to a tank. Since the pressure sense is on the other side of the check valve, seems to me this would work and make is essentially self priming. Try it and report back - save me the trouble .
All of this makes it sound like the Marco pump is a pain the butt, actually most of the time it works just ducky.