Wisely I installed one of these so I can drain the outlet pipe from macerator .

Had a few times where I need to drain it .

Problem is this cap leaks - it’s just a screw cap with a washer . I’ve tightened with grips but can’t really go any further .

Are all end caps equal ? . Nothing I can smear round the thread that will make a water tight seal but won’t glue the cap on !!? . I did think of plumbers tape - but it’s too awkward to get to …

Would a thin flat rubber washer work? pressed into the cap?, or if all else fails a 32mm air test bung.

21 minutes ago, crispy_wafer said:

Would a thin flat rubber washer work? pressed into the cap?, or if all else fails a 32mm air test bung.

That’s what it has already .

By pure luck I bumped into a plumber and just mentioned the issue .

He gave me a tube of this …. This do the job ? Ok to use ? . Not glue it !!?

The end cap should seal on the washer, not the threads, over tightening is likely to cause it to leak as the washer will be pushed out of place. Pull washer out and inspect - probably split or deformed. Replace the washer and only finger tight, problem solved

Sounds fairly suitable, see the Q&A here, they recommend some re-inforcement for >25mm dia and the joint has to be dry first and then left for 1 - 2 hrs.

 

However this will/is intended to form a seal on the threads. Personally I would want to understand how the existing seal is supposed to work, probably axial compression of the washer, and then improve it. Check there is no damage/distortion to the mating faces or a tiny sprue left from the moulding process.

 

Often the washers are too thin/too hard, a circle cut from an old inner tube might be better and less likely to get pushed out of place. Or apply a thick bead of silicone sealant inside the cap, screw on lightly and then tighten 2 hrs later once it has set.

 

Edited March 6, 20242 yr by sharpener

If it's a rubber O-ring seal, then you only hand tight. Over tightening will distort the seal and result it in leaking. You might have damaged it so might just want to replace the whole unit itself. Duct tape in the meantime.

Yeah it’s a skinny washer . Very thin . Not brittle or split . I’ll order a new end cap with washer . Replace and see . I did assume hand tighten was meant to be sufficient.

This end cap drain is right on the macerator output . So I assume bit of water pressure and vibration aren’t helping - or should an end cap ( with suitable washer ) be sufficient anyway in this situation ?

Yes