Sand Filter Leak

Jan 27, 2013
Hi All

My sand filter has developed a slow seeping leak when the pump runs from the insert unit that the barrel union threads onto. The leaking fitting is on the pool return outlet of the multiport, the filter is a Davey Crystal Clear 25 inch. I have disconnected the barrel union and then unscrewed the coupling/insert, on inspection it looks ok so I removed the thread tape and reapplied prior to refitment.

I am surprised that there is no o-ring or any other such gasket/sealer but the Davey manual confirms that its only thread tape that is used to create the seal of the threads. I have tried tightening up the fitting a bit more with a wrench but it still has that slow seeping leak there. The internal threads on the multiport look ok, I was contemplating that the thread tape may be forcing gaps in the thread at pressure but without tape the fit is pretty loose.

Can anyone suggest something else to try?


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
Do you have a picture of where it is leaking?

I've personally had better luck on large fittings using pipe dope instead of tape. Make sure you use the type intended for plastic threads or it can crack fittings.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
+1 what John said. My experience has been that pipe dope seems a little better for anything 1.5" or more.

Try it......if it works, it's a cheap fix. :D
Jan 27, 2013
Thanks for replying JohnT and duraleigh.

After further investigation it turns out to be the recent installation of a new chlorinator, I had an Astral EQ with PH & ORP probes professionally installed (only way they will sell them over here in Australia). The 'professional' had too much length on the pipe coming from the sand filter pool return, he then installed the cell too high above said port. Basically the weight of the water and leverage applied on the fitting must have been causing a small gap in the thread which in turn leaked when under pressure.

I didn't like the way he had installed the cell and the sensing chamber was put in vertical instead of horizontal as per the install manual, so I redid it according to manual and shorter length/height (like a normal install would look) and the leak from the fitting has disappeared. Unexpected but very happy all round with result.