Suction Side Leak?

[trivetman]

The last valve in my suction side plumbing before the pump pulls water from the skimmer in one port, the main drain in the other port and sends it into the pump.

One day i turned the skimmer port off on account of low water level and saw a very small amounts of bubbles being sucked into the pump. Sounds like a suction side leak right? Wierd thing is it only shows up when the skimmer port is off. When the pump is pulling from both the main and skimmer- no bubbles. Why is that? Maybe the leak is so small that air is only drawn in when the suction is all directed to the main. Other ideas?

Other part of this is that this is the valve I use to seal the air in the main drain over the winter. So if this is a tiny suction side leak that only shows up under full pump pressure, how do I know if my air column in the main drain is maintained?

 

[duraleigh]

When the pump is pulling from both the main and skimmer, there is less "resistance" on the suction side. Main drain only increases that resistance and allows the leak to show up.

how do I know if my air column in the main drain is maintained?

If I understand what you are saying, you don't. Perhaps you can replace the seal on that valve.

 

[trivetman]

That makes sense. Any idea how to diagnose exactly where the leak is? There is an elbow joint between the underground plumbing and the valve. It could be one of those joints or it could be where the pvc meets the valve.

 

[duraleigh]

Is it where you can slowly pour water over the joints? If so, it should reveal the air leak by temporarily stopping it. (a pic may help)

 

[trivetman]

Here's a pic of the pad. The leak must be in the pipe coming off from the valve closest to the pump that goes into the ground.
I was thinking of getting some silicone repair tape and just wrapping all the joints on the pipe. I'm not sure that is meant for permanent repairs, but for a leak this small I would think it's ok.

 

[trivetman]

I got the idea to test the joints like they were gas joints. Run air pressure through the pipes with a cyclone blower, rub soapy water on the joints and look for air escaping via soap bubbles. No sign of leaks there. I then wrapped each above ground joint in silicone repair tape in case I missed something but no luck. Still there are air bubbles coming into the pump.

I guess the leak must be below ground. Nothing to do about it without some major digging. Winterize as usual and hope its not worse in the spring is all I can think to do.

 

[duraleigh]

It COULD be underground but almost never is. Recheck everything in the Spring (including the drains in the bottom of the pump basket) and don't dig until you are ABSOLUTELY certain it's not in the visible pipes.

 

[trivetman]

Thanks for the help