understanding pump, filter and valve behavior

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drrayb

Well-known member
Jul 12, 2021
62
toronto, ontario
Pool Size
20000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Hello,

We just bought a house last year with a pool. We opened it this year, and with the help of this site, have learned much about maintaining it.
I have some questions about the equipment behavior that I was hoping you guys could answer.
Thank you in advance for your time.

as a rundown (also see diagram):
- 20,000gal in ground pool with 2 returns - 1 deep end surface, 1 shallow end surface at 90 degrees to each other. 1 skimmer opposite the deep end return. no main drain
- 1.5 inch piping
- 25-30ft from skimmer to pump
- 1.65HP variable speed Hayward, roughly 1.5 feet higher than skimmer intake
- no check valve between single intake pipe and pump
- 21 inch, 225lb sand filter with multi-port valve
- ancient heater
- 1 check valve from heater to pool returns

1634410299714.png
my questions:
- whenever I open the pump housing, the suction side tubing depressurizes and water level drops. I refill the housing with water before priming again. However, as soon as the pump is on, the level transiently drops back down to the bottom of the impeller intake, the pump is louder, and then 3-4 seconds later it starts filling with the suction water and primes itself fully. Is this normal? I don't like that the pump is starved of water, even for a few seconds. Should I install a check valve before the pump (on suction side) to maintain the water column while the pump housing is open?

When the pump housing opens, the filter also seems to depressurize. After I resume running the pump, and it refills with water, the filter has to purge itself of air too. It shoots a bunch of air out of the reutrns, then very small amounts of it for 5-10 minutes, and you can hear air in the filter body for some time, but gradually it gets rid of it all. Is this normal?

Whenever I rotate the multiport valve, that is, whenever I press the handle down, the filter depressurizes itself as well. This also leads to some air bubbles going back into the pump. Is this normal?

Again, I am trying to avoid situations where any air is introduced into the pump and causes it to run (even if partially) dry.

Final question - does anyone have advice about improving flow in the right lower corner of the pool (closest to the equipment pad) where there is no return jet. It is the main dead area of the pool. I was considering one of those rotating jets with gears in them.

Thank you very much!!
 
Last edited:
What you describe is normal. Most pumps are self priming and designed to handle a few minutes starved of water. My filter also drains when i open the pump lid. There is a valve on top to allow the air to exit. Make sure you're opening that valve as needed when the filter drains until water squirts out.

Dead areas are tuff. What you suggest might work. Do you have eyeballs on the returns?
 
drrayb said:
whenever I open the pump housing, the suction side tubing depressurizes and water level drops. I refill the housing with water before priming again. However, as soon as the pump is on, the level transiently drops back down to the bottom of the impeller intake, the pump is louder, and then 3-4 seconds later it starts filling with the suction water and primes itself fully. Is this normal? I don't like that the pump is starved of water, even for a few seconds. Should I install a check valve before the pump (on suction side) to maintain the water column while the pump housing is open?
Click to expand...
3-4 seconds is OK to regain prime. A check valve can help maintain the water in the pump but the level still may drop some as the pump suction also has to overcome the friction to move the check valve open. Do you have room to add a check valve?
drrayb said:
Whenever I rotate the multiport valve, that is, whenever I press the handle down, the filter depressurizes itself as well. This also leads to some air bubbles going back into the pump. Is this normal?
Click to expand...
On a multiport valve it is moving the opening between filter and backwash and waste lines so yes it will allow air to get back into the system. I find it best to relieve pressure from on top the filter (noted below if you have a relief valve), then move the multiport valve. This takes the pressure off of the spider gasket in the multiport valve as those can be a challenge to change if you damage it by moving the multiport handle with pressure on the system. Once done and go back to normal filtration position, start the pump and relief pressure from the filter. So if you do not have a relief valve on the filter, it can be handy.

Also, on a multiport valve, it is always good to push and pull up on the handle once or twice before you move it. This breaks the friction of the valve sitting on the spider gasket. Also, it is recommended to rotate the handle in one direction, ie. clockwise to move between various positions.

drrayb said:
When the pump housing opens, the filter also seems to depressurize. After I resume running the pump, and it refills with water, the filter has to purge itself of air too. It shoots a bunch of air out of the reutrns, then very small amounts of it for 5-10 minutes, and you can hear air in the filter body for some time, but gradually it gets rid of it all. Is this normal?
Click to expand...
Do you have a relief valve on top of the filter? It is sometimes below the pressure gauge. Once you start the pump and everything is primed and water flowing, you can open the relief valve to remove the air from the top of the filter. Post a picture of your filter. You may be able to add one if you all you have is a pressure gauge directly into the filter top.


Include a picture of your equipment if you have any further questions.
 
PoolGate said:
What you describe is normal. Most pumps are self priming and designed to handle a few minutes starved of water. My filter also drains when i open the pump lid. There is a valve on top to allow the air to exit. Make sure you're opening that valve as needed when the filter drains until water squirts out.

Dead areas are tuff. What you suggest might work. Do you have eyeballs on the returns?
Click to expand...
Thank you Poolgate!
I have the hayward SP0714 multiport valve. no pressure relief valve but the pressure gauge unscrews to release the pressure. Is it harmful to let the air leave through the returns? I have tried to open it twice while the equipment was priming and washed the entire interior of my pool shed.

regarding returns, I have eyeballs. I set the shallow end one to blow straight, superficially and the deep end one to blow deep into the water.

HermanTX said:
3-4 seconds is OK to regain prime. A check valve can help maintain the water in the pump but the level still may drop some as the pump suction also has to overcome the friction to move the check valve open. Do you have room to add a check valve?

On a multiport valve it is moving the opening between filter and backwash and waste lines so yes it will allow air to get back into the system. I find it best to relieve pressure from on top the filter (noted below if you have a relief valve), then move the multiport valve. This takes the pressure off of the spider gasket in the multiport valve as those can be a challenge to change if you damage it by moving the multiport handle with pressure on the system. Once done and go back to normal filtration position, start the pump and relief pressure from the filter. So if you do not have a relief valve on the filter, it can be handy.

Also, on a multiport valve, it is always good to push and pull up on the handle once or twice before you move it. This breaks the friction of the valve sitting on the spider gasket. Also, it is recommended to rotate the handle in one direction, ie. clockwise to move between various positions.


Do you have a relief valve on top of the filter? It is sometimes below the pressure gauge. Once you start the pump and everything is primed and water flowing, you can open the relief valve to remove the air from the top of the filter. Post a picture of your filter. You may be able to add one if you all you have is a pressure gauge directly into the filter top.


Include a picture of your equipment if you have any further questions.
Click to expand...
Thank you HermanTx. We are away from the house but I can take a picture later if needed. As mentioned earlier, the pressure relief valve on the filter valve is just unscrewing the gauge a bit. Is that sufficient? I will do the things you said for the multiport valve day-to-day use.

Regarding the suction line, where it emerges from the ground, first is a 90 degree turn, then about a foot of straight pipe, then another 90 degree turn right into the pump...so I suppose there is room, but less than ideal.

Thank you again
 
drrayb said:
Thank you Poolgate!
I have the hayward SP0714 multiport valve. no pressure relief valve but the pressure gauge unscrews to release the pressure. Is it harmful to let the air leave through the returns? I have tried to open it twice while the equipment was priming and washed the entire interior of my pool shed.

regarding returns, I have eyeballs. I set the shallow end one to blow straight, superficially and the deep end one to blow deep into the water.


Thank you HermanTx. We are away from the house but I can take a picture later if needed. As mentioned earlier, the pressure relief valve on the filter valve is just unscrewing the gauge a bit. Is that sufficient? I will do the things you said for the multiport valve day-to-day use.

Regarding the suction line, where it emerges from the ground, first is a 90 degree turn, then about a foot of straight pipe, then another 90 degree turn right into the pump...so I suppose there is room, but less than ideal.

Thank you again
Click to expand...
Pictures will help with regard to the suction for the pump.

I would not unscrew the pressure gauge each time to relieve pressure. That is dangerous, wears out the threads and as you say sprays your whole area. You can either buy something or make it with a tee joint if you really want it. Having bubbles flow to your returns is no big deal. Again pictures will help of the filter.
 
 
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