pumping rainwater cistern

Old 06-04-08, 05:36 PM
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pumping rainwater cistern

I have installed a 500 gal septic tank as an underground cistern to catch rainwater from my roof. The tank accumulates aggregate from my shingles so I do not want to use a pump with a foot valve because it will very likely leak due to trapping this debris. I have installed PVC dip tube in the tank and an in-line filter at the other end to trap the debris. I plan to clean the filter as needed. I need a pump to draw from the tank (max draw depth is 5 feet) and store it in a pressurised captive air tank much as a well water system does. Given my current setup what kind of pump do I need? I have tried to prime a centrifugal pump but no luck.

Old 06-04-08, 06:10 PM
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"I have tried to prime a centrifugal pump but no luck."

Did you put a foot valve on the end of it?
To prime, you would put priming water in to fill the intake pipe back to the foot valve and the pump. Might ake two or three attempts.
Old 06-04-08, 06:43 PM
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You can't prime it with out a foot valve.
Old 06-04-08, 07:14 PM
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I'm not quite sure that I understand everything, but I think you'll be fine with a centrifugal pump. Using a footvalve will facilitate priming the pump. Do not use the filter on the suction side of the pump, but rather on the discharge side.
If you're using the system to irrigate with, we'll need to know what kind of capacity you'll need before a pump can be sized.
The aggregate from the roof is going to get in the tank no matter what, but it should settle out and not be a proiblem.
You will, however, probably need to clean the tank once in a while.
Old 06-04-08, 09:18 PM
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this is kinda cool. if this was mine, rather than having a foot valve in the tank at the bottom of a drop pipe, i would use an in-line check valve somewhere between the suction of the pump and where the line goes in the ground to the tank. if you dont, you will be digging every time that foot valve hangs up. might take a little longer to prime it all, but it would be ALOT easier to take apart and clean out when it hangs up. just my 2 cents. seems like you could rig a little home engineered somethin to let that water run through some kind of screen before it goes into the tank. definitely no filter anywhere in the suction.

Last edited by justwater; 06-04-08 at 10:33 PM.

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