I have a Hayward Multiport and Sand Filter Valve air leak

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jlbaker999

jlbaker999

Member
Jun 9, 2018
12
lubbock,tx
I replaced this Multiport valve ( the old one lasted probly 10 years. Anyway, over the last several months there seems to be an air leak on the sand filter outlet side. When the valve is set to filter there is an audible "buzz" is the only way I can describe it. After several pump cycles air builds up in the sand filter and when the pump turns off the air pressure pushes back through the inlet lines to the pump and it sometimes takes a long time to reprime the pump and start pumping. If I run the water to any of the other valve outlets (recirc, waste, etc) there is none of the buzz. If I bleed the air pressure off the sand filter it runs fine for a few cycles. I've checked the star seal on the valve plate and it seem fine. The sealing surfaces inside the valve body seem clean and smooth. What do you think ???
 
I did not take the valve apart when it was new (a year or two ago) but when I looked at it earlier this season I lubed it when I put it back together. The seal looked ok, no rough spots, etc. I think this valve is a 710 series Hayward Multiport. It's really odd, there should be no reason for air to get into the valve, which is, of course, on the pressure side of the pump. And the air gets into the sand filter (which is old, same one that was on the pool when we bought the house in "91). Really a brain twister. I've been working with this system for 30 years and I've had air getting into the pump on the suction side on several occasions but that doesn't seem to be the issue this time. I should check the pump housing gasket. That's one thing I haven't done. I replaced the pump "innerds" earlier but they sent the wrong housing gasket so I used the old one. That might be the problem.
 
I have no explanation but do have a similar issue with my Hayward multiport valve. When the pump switches off, air gets into the filter via the valve. No leaks but definitely associated with the valve, not the rest of the plumbing. This happened to the previous valve also; replacing the valve stopped it for a year but then the issue reappeared.
 
That is a suction side leak. Air is being sucked into your system and pressurizing the filter. The multiport valve is on the pressure side of your system so the issue is not there.

It is somewhere between the skimmer and the pump. Can you see air bublles sloshing in the pump basket lid?
 
jlbaker999 said:
I replaced this Multiport valve ( the old one lasted probly 10 years. Anyway, over the last several months there seems to be an air leak on the sand filter outlet side. When the valve is set to filter there is an audible "buzz" is the only way I can describe it. After several pump cycles air builds up in the sand filter and when the pump turns off the air pressure pushes back through the inlet lines to the pump and it sometimes takes a long time to reprime the pump and start pumping. If I run the water to any of the other valve outlets (recirc, waste, etc) there is none of the buzz. If I bleed the air pressure off the sand filter it runs fine for a few cycles. I've checked the star seal on the valve plate and it seem fine. The sealing surfaces inside the valve body seem clean and smooth. What do you think ???
Click to expand...
Neither the filter nor the valve can be the source of air when the pump is running. Any air build-up would come from a suction leak somewhere before the pump or at the pump itself. Any leak in the filter would result in water spraying out as it would be under pressure only.
 
Yes, ordinarily, this would make sense. But there's no other evidence of a suction side leak (air in the pump basket, bubbles while the pump is running (after the initial air is blown out). And why would changing the MPV for a new one stop this if there's an ongoing suction side leak?

Curious and confusing!
 
I don't really understand the two above posts but pressurization of the tank can only be caused by the pump pushing air into that tank.

When the pump shuts off the pressurized tank pushes the water backwards through the pump.

OP has a suction side leak occuring sucking in air somewhere between the skimmer and the pressure side of the pump

But there's no other evidence of a suction side leak (air in the pump basket, bubbles while the pump is running (after the initial air is blown out).
Click to expand...
It just hasn't been found yet.
 

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