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Old 12-07-2013, 05:50 AM
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1idejim 1idejim is online now
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Join Date: Jul 2009
Location: State of Jefferson
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Originally Posted by stebs View Post
Not sure I can agree with that... The pressure at the return fitting will almost always be less than pre-filter pressure... In a sand filter, the filter itself is the biggest restriction. Cartridge filters, especially oversized ones, the wall fittings are most likely the biggest restriction until the cartridges start to load up...

One of my pools used to have a large sand filter on a 1hp pacfab challenger pump and would run about 17 psi clean with 1.5" plumbing throughout. Owner replaced the sand filter with a very large pentair cartridge filter that ran about 5 psi clean. The pump was extremely noisy after this change because it could not suck enough water to fully load up. I ended up manifolding the suction side with 2" which helped it draw more water, quieted it down quite a bit and bumped my clean pressure to around 10 psi.
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My suction is always .5" larger than my returns. Typically 2.5 and 2.0 respectively. A certain amount of back pressure is required for proper operation. As I said 8-12 psi is optimal at the filter.

I may be over thinking this and may be wrong, I may be trying to confuse flow and pressure in my theory. Centrifugal pumps are easy to work on but the actual diagnosis can be confusing at times. That's why so many pumps are R&R if it's not the obvious impeller, bearing or seal.

We'll see next year, I'll install a gauge or two close by and monitor them.

Thanks for replying stebs, you don't post often enough and have a lot to bring to the forum.
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