PSI lowers when turning on waterfall

[Mode16]

Hey all, I have a 36,000L underground salt-water pool. The pool is about 15 years old. When running smoothly, the PSI is always at a nice 17 which is what the installers mentioned when we first bought the pool.

One thing I am not understanding though is... why does this lower to 12 when I open the waterfall?

From my understanding, the waterfall's water comes from a return pipe. I thought PSI measured the pressure from water coming INTO the filter and not out of the filter. Is this wrong? Any help would be greatly appreciated.

 

[ajw22]

The PSI measures the pressure through your plumbing until the water comes out returns.

A waterfall is low head and reduces the overall back pressure and restrictions in your plumbing so the filter PSI goes down. The waterfall gives an easier path for the water to flow out.

 

[Mode16]

Okay got it thanks! Will having the waterfall on affect suction on the drain or skimmer?

 

[ajw22]

Okay got it thanks! Will having the waterfall on affect suction on the drain or skimmer?

No, it should not.

 

[JamesW]

Okay got it thanks! Will having the waterfall on affect suction on the drain or skimmer?

Lowering the pressure on the return side can increase the flow, which will make the suction stronger.