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+--- Thread: filter location (/showthread.php?tid=17196)
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RE: filter location - terracore - 05-13-2016
Combining my dated industrial career dealing with hydraulics and my high school physics class... if you put the filter before the pump/tank/pressure switch, as the filter begins to restrict flow to the pump the inlet pressure becomes higher (like sucking water through a straw rather than a plumbing pipe) than the outlet pressure. The pressure switch is calibrated for the restricted flow to be on the other side of it- so your pump will cycle on/off more often if the filter is before it. So regardless of how the filters were engineered to function (push versus pull) the pump/pressure system will be more efficient if the filters are after the pump.
All of our plumbing systems are designed by the "pushing" water theory... water pressure has historically been provided by gravity. "Pulling" systems are sometimes superior, because water that is sucked via vacuum through a cracked pipe doesn't leak (though the pipe will take in air etc and that has to be dealt with) and pulling requires more energy. I think I've digressed quite a bit but the pressure switch is expecting the filters to be behind it, not in front.
RE: filter location - Tink - 05-13-2016
Best way I have found is first a debris filter(to keep impeller/diaphragm from damage, pump/pressure tank, then the micron step down (5/3/1) and finally uv.
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RE: filter location - Hunt Stoddard - 05-13-2016
@terracore
Hmmm, interesting, the one complaint a person using this system had was air in the water, which could perhaps happen if the filter canister wasn't on tight enough. Air would be sucked in, but there might be no leak?
RE: filter location - MarkP - 05-14-2016
FWIW I selected a filter for the suction that had the largest and least restrictive rating that I could find. Locally that means 30 microns. I could probably get 50 microns if I ordered online. Let's not get hung up on terminology. I have a very fine strainer (30 microns) on the pump suction floating in my tank. After the pump but before the expansion tank I have a very, very fine filter (0.1 microns) that is supposed to filter out everything except viruses.
RE: filter location - terracore - 05-14-2016
quote:
Originally posted by Hunt Stoddard
@terracore
Hmmm, interesting, the one complaint a person using this system had was air in the water, which could perhaps happen if the filter canister wasn't on tight enough. Air would be sucked in, but there might be no leak?
I guess its possible, but it would be hard to imagine a scenerio with negative pressure like that all the time.
When I worked in industry we used vacuum systems for liquid coolant all the time. Even a pinhole leak could cause catastrophic damage so pumping the coolant through wasn't an option. We could tell when there were leaks because the vacuum units had systems that removed the air from the coolant and the worse the leak, the more air, and the less efficient that unit became.
In researching a problem with my car's gas tank (posted under a separate thread) I found out that if the gas tank's air vent line gets kinked or clogged the fuel pump can actually collapse the gas tank. That's got to be a lot of stress on the pump. I imagine the same strain can happen to the pump in a water system that is forced to pull water rather than push it.