Water hammer when vacuuming?

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DesertJon74

0
May 2, 2010
72
Palm Springs area, CA
I recently installed a 2 speed pump and have noticed when I'm done manually vacuuming and turn the pump off there is a noticeable "thump" sound coming from somewhere between the pad and the pool. I can also "feel" the thump somewhat.

I tried going from high speed to low speed to see if that made a difference and it still makes the noise. It only happens when vacuuming, not during normal operation.

My psi is normally around 18-19 psi and drops to 13 while vacuuming on high speed. The two suction lines are 2 inch pipe and one return is 2 in and the other is 1.5 in.

Any thoughts on what the noise could be?
 
Using the hole at the bottom of the skimmer is fine. You thump can't be related to that.

An SVRS system would make a thud if it triggered. An SVRS is a special valve that lets air into the system when someone is stuck on a drain cover. They are fairly rare however.
 
If you are drawing a vacuum and shut down a pump you can cause a water hammer as the water floods back through the now stopped pump. But if the flow is that restricted during vacuuming the pool then you don't need to have it on high speed. Having it on the lower speed before shutting down should also reduce the water hammer.
 
Is it possible to vacuum on low speed?

I've started going down to low speed before shutting off the pump.

I think I made a mistake going with this pump. I tried to match the total horsepower of the old starite because i have a spa, but it seems substantially more powerful. It may even be too much for my cartridge filter. I'm noticing more dirt bypassing the filter while I vacuum.

Should have gone a half horse lower.
 
I believe ther is a spider valve on the suction lines where they converge at the jandy automatic valve.

- - - Updated - - -

There is a spa drain (two of them) and the main drain.

At the bottom of the skimmer there are two holes. Am I correct that one of them comes from the main drain?

There are two suction lines at the pad.
 
A lot of skimmers have two ports in the bottom, with one of them sealed off just below the skimmer.

If you have two suction lines running to the equipment pad, they are almost certainly main drain and skimmer(s). When the main drain is plumbed to the skimmer there is never more than one line to the equipment pad.
 

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I changed my pump to a new high efficiency Pentair VS. I have noted that if I'm running it at a higher speed it will thump when shut down unless I change to a slower speed first.
 
Have you let all of the air out of the filter? Or does air accumulate in the filter each time the pump is run?

Hopefully this isn't it, but it could be that you are running the pump at too high of a speed, and the filter is deforming, with a thump when the pump goes off and it returns to it's normal shape. If so you would definitely want to turn down the max speed setting.
 
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