Pool suction line union question

[bwoodland]

Hi All,

Moved into this house in 2022 and inherited the pool and hot tub with all of their problems. Pool is losing 1-1/2 inches of water a day and one pool company employee mentioned that they did a pressure test and could not maintain pressure on suction side, but it was second hand to me and not in writing. Many of the pool companies in my area are terrible at customer service and very often are no shows for appointments, so I've been learning a lot from youtube and forums here (and have some prior experience from the onground pool and good pool companies at the last place I lived).

I've rigged up a pressure testing system and am about to start but I have two union related questions. I might not get an answer that I can work with on the pump question, but hoping that someone recognizes the union in the pic for the second question.

1. Does anyone know the male pipe thread size of fitting that I'd need to connect to the union that connects to my hayward super 2 pump? The plumbing is 1-1/2" and the pump union has RS750 written on it, but the size of the fitting to match that pipe thread is a bit of a mystery. Hoping that someone knows that size so I don't have to unscrew the union to measure.

2. (pic attached) - Suspecting a leak at or near the skimmer. Hose comes out from underground just past the pool deck, and under the patio deck, and then runs over ground (under deck) to pool room that is in the garage. I'm going to start digging first but was wondering what this union was - maybe a check valve? Sounds like it's sucking air (gurgling a little), but I dont think its the source of the leak, because the ground is not so soggy beneath it, and it seems I'm loosing a few hundred gallons a day (I think). Ignore the dark grey hose - its just a garden hose that's going to the hot tub (out of frame).

 

[1poolman1]

RS750 is a Hayward pump union fitting. It may be 2" with a 1.5" reducer busing in it to use that 1.5" flex pipe. It is designed to be used with the threads on that pump only. The internal threads of the pump inlet and outlet should be 2" FIP. It is best not to pressure test the pump itself. The pot is not designed to hold pressure and can be damaged.

The coupling in the picture appears to be a compression coupler that doesn't work well on flexible pipe. It could be the source of a suction leak. If so, it could also leak water back from the pump/filter with the system off.

 

[bwoodland]

Thanks for the info!

For 1, I wasn’t planning on testing the pump itself but instead finding a male pipe thread fitting to mimick the pump connection to suction line, disconnect the plumbing from the pump intake, and test pressure between the fitting and that end and the skimmer. Tell me if that logic isn’t sound.

For 2, if that’s not a check valve, and you mention water going back into pool from pump/filter, should I replace with a check valve, or just a coupling?

 

[1poolman1]

A leak in the suction plumbing can be anywhere in the line. Most commonly, according to the leak-detection guys I know, it will be found in a fitting and then it is usually a 45.
1. - Sound if you can find a way to attach to a proprietary union.
2. - Not sure what that is. Looks like a compression coupler. Could be a combo of both, check valve/coupler. Many put a check valve before the pump, many between pump and filter. I don't have either and have no issues. Depends on what you want to accomplish. If you put a check valve anywhere, be sure it one like a Jandy that can be rebuilt rather than cut out, as needed.