Plumbing Leak Repair - Hepvo Sink Drain

BrianZ

I'm posting this info about our under-sink drain plumbing as a reminder to check your slip joint connections periodically. If you have them, these hand-tightened joints can work loose over time and start leaking.  I learned this lesson while at the dump station recently.  Also, I'll show you a simple replacement part that may give a more secure connection.

Like many others, I used @Dale Helman's excellent idea to gain space under our T@B sink by installing a Hepvo valve to replace the P-trap, and it has worked wonderfully for years.  A year later in 2019, we added yet another valuable Helman idea by adding a door to our outside plumbing vent, so we could flush our black & gray tanks at the dump station by inserting a water hose.  This too has been a great help - one of the best ideas yet!

This year however, four years after the plumbing work, when shooting water into the plumbing vent to fill the gray tank, we got water squirting out from under the top tightening nut at the location indicated by the blue drops below..

There didn't appear to be any other leaks, though I would expect the two top locations indicated by arrows would be most vulnerable, since they have a smaller diameter pipe going up inside of a larger one.  As a result, the gasket around the smaller pipe gets hit directly by the stream of water & will leak if the gasket ring &/or nut is not seated tight enough.  At the time I installed the leaky pipe joint at the top left, it was only serving as a gas vent, so I never anticipated that a stream of water would ever be squirting down that pipe!  Below is a closer look at the leaky section of pipe..

The tightening nut at the bottom right had been at top of the pipe and was the source of the leak.  The red arrow points to the built-in gasket ring, which is a stiff plastic that is part of the nut.  I moved this leaky nut to the bottom of this short pipe which empties into a larger pipe, so it won't be subject to a direct stream of water.  That was half of the fix, because the other tightening nut I moved to the top had been using a separate but similar type of hard plastic gasket ring.  I removed that and replaced it with the softer red rubber gasket for a better seal at the top. (See last photo for source info for this red rubber gasket, which I've seen recommended as a replacement for a better seal.)  

Here's a view of the reassembled section of pipe, with top at left..

And below is the replaced section of leaky pipe with new rubber gasket.  I also installed a rubber gasket in the similar top right junction.  Several joints also needed additional hand tightening after 4 years of use.

I also replaced the piece of foam pipe insulation below that helps hold a water hose in the plumbing vent pipe while preventing backflow from running down your arm. Thank you, @Homebodyatheart for that mod-the-mod!   I added a strip of 3M heavy duty outdoor double stick tape to secure it - my mod of the modded mod. (Mod³)..

And last, here is the info on the red rubber gasket ring I used (this package also comes with a 1-1/4" pipe adapter washer, which isn't needed for this 1-1/2" pipe)..

Everything is now tight & leak-free, but I'll need to remember to check those pipes every year or two!  Expecting it will last longer with the more grippy rubber (vs. the old hard plastic).