Pressure drop on sand filter

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ned8377

ned8377

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Apr 30, 2015
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Wake Forest, NC
Anyone know what would cause the pressure to drop about 4-5 psi on the sand filter for no apparent reason? It has not been back washed etc. Could it have developed a channel through the sand? I've seen it do this once before and then it would go back to normal pressure after a while. Thanks.
 
Did you remove a cleaner or turn any of the valves? You didn't backwash before the drop I take it? If you're concerned about sand channeling you could always pop it open and look. Perhaps give it a little clean while in there..... Just a suggestion ;)
 
No didn't change anything. Actually, the only other time I noticed it was after a back wash and then a couple of hours later it was back to normal. This time, I have not back washed. Went outside to check things and noticed pressure had dropped. Thanks!
 
PSI drops because of decreased flow on the suction side. Of course, a faulty gauge can be an issue, but typically, you will find some obstruction somewhere between the impeller on the pump to the skimmer(s).

Most folks assume the worst and think it is the underground pipe.........while it can be, it almost never is.

What have you inspected so far on the suction side of your system.
 
Ok, I went out and emptied all the skimmer baskets and pump strainer. Not sure how to check the impeller. Ended up with same pressure. Then I backwashed as usual and it went back to same pressure. You are right that an obstruction could decrease pressure since turning off the main drain or skimmer will do the same but they are all on. I have a return jet in the shallow end that blows close to the top of the water so I can visually see the circulation and it is better than it has been in the past. All the skimmers seem to have good circulation. When turning off the main drain pressure drops further as it should.

I've always had a problem with the pressure running too high in my opinion at about 26 psi after a backwash. I would wait for it to get up to no more than 35 psi before backwashing again and it would always go down to about 26-27 psi. Now it is running at 20 psi which is more in the range of where it should be.

If the flow, from the return jet, in the shallow end is, visually, at least or greater than it usually is and all the skimmers seem to be sucking normally, am I right to assume there is probably no obstruction?

Thanks for your help!
 
Now it is running at 20 psi which is more in the range of where it should be.
Click to expand...
Why? What is different from when it was at 26 psi?

Decreased pressure (that's you) and an increase in flow (that's apparently you, too) indicate you have removed a restriction from the pressure side of your system.

When did that drop in psi occur?
 
Maybe the gauge is defective. We had weeks of rain starting around Sept 24 here in NC. Ever since then there have been droplets of water inside the gauge that won't go away. Went out and started the pump this morning and now pressure has moved from 20 psi to about 24 psi. You can see where I used to have it set at 26 to about 35.

20151019_105222_zpsl2s9d0q0.jpg
 

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I think it might have something to do with withstanding lower cold temperatures as well as smoothing out the needle when it moves, but one thing I did not like about it then
changed my mind is the bubble showing at the top of the rear mount one.

Then I realized the left and right edges of the bubble is the exact area where markings would be for "time to back wash"
and "just backwashed" areas of the gauge...at least on my pump/filter setup it is.

Most residential pools should not need a gauge going beyond 30.
 
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