Isolating air leak

[Styxbb]

Opened my pool on Monday. While SLAMming, noticing lots of bubbles coming from return jets. I've narrowed the leak to somewhere on the skimmer side of the 3 way diverter valve(no bubbles when using only port 2). My suspicion is the union is leaking because it is on that side of the valve. Otherwise, I'm thinking cracked line somewhere on the skimmer side. Is replacing that valve my first step?

Thanks

 

[duraleigh]

Before you replace it, I would experiment just a bit with resealing it? Do the connections all look straight? any obvious signs of cracks.

On the suction side, you can often temporarily stop a leak by caulking it. It's not permanent and it won't work at all on the pressure side but it might help you identify it.

 

[Styxbb]

I loosened the union yesterday to try and move it around and check it, but it is firmly in place. I thought about caulking it. It is 26 years old now. There are some cracks showing along the threads to my pump line because that's where I disconnect it yearly when closing. Originally, I thought that was the culprit, but it only leaks air on Port 1.

 

[duraleigh]

Pump running, it should suck air into the system.....is it doing that?