Extremely strange suction side leak

[generessler]

Sigh... Need help from the wizards again... You guys have been soooo... helpful in the past.

When our pool is in pool mode, there's zero air visible. All is fine.

But in spa mode, it draws air. Easy to see in the pump basket. Clouds of bubbles from the spa returns. When I turn on the heater, the bubbles eventually slow down and seem to stop, but there's still air visible in the pump.

This has been happening for most (maybe all) of the 19 months we've owed the pool. We only use the spa a few hours a month. It works great despite the bubbles.

But it's been bothering me. I know air in the pump is bad. I've been reading and poking around for months. At this point I'm stumped. Help!

Here's the suction side of the pool pad. The spa water level is the same as ground level in this picture, maybe a couple of inches lower. The leftmost pipe is the spa drain. The valve is in "pool mode" position: spa off.


For a long time I thought the only place the leak could be is in one of those left side PVC joints or maybe the left side of the valve. If it were closer to the pump, I'd see air all the time. If air were entering closer to the pool (from under ground), there'd be a water leak. Thank goodness there's none, at least that's noticeable.

So I tried duct taping all the PVC joints. I changed out all the O-rings in the valve and used a lot of lube. Just to be sure, I tightened and lubed up the threaded joint on the pump, lubed and snugged the union, and changed O-rings at pump basket and all the drain plugs. I looked for cracks and tried the incense and garden hose methods. Nothing.

This past weekend I fiddled some more. I removed the actuator and moved the valve manually. Found out the air only appears when the valve is about 3/4 the way from pool to spa. That is, the pool suction side needs to be nearly shut off.

I think this means that the amount of suction on the spa side matters. It needs to reach some fairly high value before the leak opens. That's pretty scary. How on earth can I figure out a leak that needs full suction before it appears?

The other thing I noticed is that if I turn the valve quickly from pool to spa, air shows up in the pump only a few seconds later. Maybe 3 or 4. What does this mean?

My only idea at this point is that maybe the leak _is_ at an underground joint a few feet down the drain line. It takes those seconds for air to get from it to the pump. It doesn't leak water because it seals back up with suction removed. Maybe this fits with the leak getting smaller with the heater on. The pipe expands a little and partially seals it.

All this seems too complicated, and it makes me sad. There's some beautiful landscaping around the pad. Digging it up would be really painful.

Sorry for the long saga. But maybe somewhere in this will be a bit of info that an expert can use to see what's happening.

What do you think? Cheers and thanks.

 

[1poolman1]

An often overlooked suction leak is found at the stem and lid "O" rings of the valves. Pull the actuator off the valve then pull the lid. You will find a very thin "O" ring at the lid and 2 rings in the stem. Put some pool lube on the lid ring after carefully removing it and cleaning the lid. On the stem, after cleaning, be sure to put some lube. On valves as old as yours I will put a wrap or two of Teflon tape and then a little more grease.

You can get new "O" rings at a pool supply and then do the above. DO NOT use a power screw driver to reinstall the screws. The valves are easy to crack doing this when new and yours are older.

 

[generessler]

An often overlooked suction leak is found at the stem and lid "O" rings of the valves. Pull the actuator off the valve then pull the lid. You will find a very thin "O" ring at the lid and 2 rings in the stem. Put some pool lube on the lid ring after carefully removing it and cleaning the lid. On the stem, after cleaning, be sure to put some lube. On valves as old as yours I will put a wrap or two of Teflon tape and then a little more grease.

You can get new "O" rings at a pool supply and then do the above. DO NOT use a power screw driver to reinstall the screws. The valves are easy to crack doing this when new and yours are older.

Thanks! I did replace those O-rings last weekend. Everything inside looked pristine. I guess to rule that out and maybe some other possibilities I'll try the saran wrap thing.

Added

Yeah this past weekend I tried wrapping the whole area carefully with saran wrap. By the time I was done, looked like the mummy. No change. So I remain stumped.

The other thought I had is that I intend to replace the 1.5 hp whisperflow in the picture with Intelliflo VS. I guess that if I limit the speed in spa mode, the suction won't be high enough to open the leak. Of course it needs to be high enough to keep the heater happy.

Sigh... It's just a hole filled with water...

 

[Nitramnayr]

I have a very similar situation to yours. My next step will be to replace the valve. I don’t believe you or I have an underground leak as there isn’t presumably any dirt entering the water flow. For ours, the faster we run the pump the less air bubbles we get in the basket. Good luck to us both!

 

[generessler]

I have a very similar situation to yours. My next step will be to replace the valve. I don’t believe you or I have an underground leak as there isn’t presumably any dirt entering the water flow. For ours, the faster we run the pump the less air bubbles we get in the basket. Good luck to us both!

Thanks! You could be correct. There might be some wear in the valve mechanism that let's air in under high suction conditions. Please let us know how it turns out!

But I'm leaning toward my problem being underground. It seems to improve quite a lot after a heavy rain when the soil around the pad is sopping wet.

Also, for unrelated reasons I recently replaced the big 1.5 hp single speed pump with a VSP. By setting the speed lower in spa mode (50 cfm rather than 90 that the old pump was doing), there isn't enough suction to cause the problem, at least for the time being.