Vacuum gauge on the drain port of a pump. What is the average readings?

[tedwagner64]

IF I have 3" of water collum on the suction side of my pump, that converts to about .25 inches of mercury. Does that mean the piping and everything is in good shoes. I mean if the pump was sucking 14 inches of mercury its wrorking really hard. So Little to no vacuum on the drain port is a good thing as long as i am maintining 12 psi at the filter gauge correct? Everyone in the forum said i had low vacuum or no vacuum replaced the gauge and never told us the new gauge vacuum reading. I think 0-10 inches on the drain port is ok. ten inces is worse that 1/4 inch right.

 

[tedwagner64]

ok i have a 1.5 hp 19 inch hydro tools sand filter. 21 foot round pool 52" been having alge problems thats why i started looking into the flow rates. Pump is rated at 75 gpm and the filter is 40 max. I been running 50 foot of pipe 2" pvc on suction and return with about seven long radius 90s and to 2-1-1/2 adapters on each line. I thinking the pump was pumping so much for the last three years i channeled the sand in the filter?
i never seen it really move above 12 psi so i used a u tube manometer and read about 3" of water collum on the drain port.

 

[mas985]

I mean if the pump was sucking 14 inches of mercury its wrorking really hard.

Actually, just the opposite. Suction and pressure are a reflection of head loss in the plumbing. The higher the head loss, the lower the flow and the lower the load on the pump. Lower head loss results in higher flow rates and higher motor load.

So Little to no vacuum on the drain port is a good thing as long as i am maintining 12 psi at the filter gauge correct?

Yes, low vacuum is fine for a pump and even preferred.

ok i have a 1.5 hp 19 inch hydro tools sand filter. 21 foot round pool 52" been having alge problems thats why i started looking into the flow rates.

Algae has nothing to do with flow rates but everything to do with chemistry. Post a full set of test results including CYA.

Pump is rated at 75 gpm and the filter is 40 max.

That doesn't mean there is 75 GPM going through the filter. A pump never runs at the rated flow rate. That is simply the maximum flow rate if there is no head loss in the plumbing which never happens.

Is that a matched filter/pump set sold together. If so, then that is not an issue.

 

[JamesW]

IF I have 3" of water column on the suction side of my pump, that converts to about .25 inches of mercury.

I used a u tube manometer and read about 3" of water column on the drain port.

That's really low.

How far is the vacuum gauge below the surface of the pool water?

Can you show the test setup?