Sealing Macerator Inlet Elbow

[Joe2954]

The macerator inlet elbow is threaded on. Factory used Boat-Life Caulk or similar. The joint leaked a few years ago. I cleaned and tried teflon tape. It has leaked again. Threading to snug takes the elbow about 1/4 turn past where it needs to align with hose.
It is on the suction side of the pump, but below the top of the holding tank by about 4 feet. Once the siphon has started, it will continue to flow even if pump is stopped.
What is recommended to seal the threaded joint?

 

[Kettlewell]

I have found that silicone caulking works well for sealing joints in the plumbing system. I've used Permatex blue gasket sealant before to seal up the inlets and outlets from my holding tank.

 

[Ralph Johnstone]

Try using about 10-12 wraps of teflon tape for bulk between the threads and wipe the outside of the tape with Permatex 2 before assembly. With this mess on the threads, you don't really have to reef the fittings too hard to ensure a permanent watertight seal.

 

[thinwater]

Consider yellow natural gas teflon tape. It is softer, thicker and seals better when high temperatures (steam) are not an issue. Silicone is not professionally used in this application; long term, particularly with any movement, it will fail, complicating future repair.

Talking about movement, if the fitting is less than snug, is movement causein the leak? should something be better secured?

Also take a very close look at the threads. It is probably one part is damaged.

 

[tahomathundr]

I used teflon tape and no problems in 4 yrs. Be careful to not get it too tight trying too line up the hose. Catalina did that and cracked the fiting on the back side and caused a great mess when the tank was almost full. Cleaning the bilge was not fun. Also if your setup is anything like mine, make sure when you shut off the macerator that you close the seacock. On my boat while sailing the system will create a reverse suction and fill the tank with seawater. My dealer forgot to close it on delivery and my tank was full.

 

[eherlihy]

I would suggest that you try Pipe Dope.

 

[Joe2954]

I believe I have it back together and sealed. I discovered that the existing fitting was bottoming out before snugging up. The male portion on the pump appears to be NPT but the female on the elbow measured too big - it may have been straight thread.
A PVC elbow snugged up after only about 4 turns but wouldn't push all the way into the Trident hose even though the hose was loose on the old elbow.
So I took Thinwaters advice and wrapped the pump end with several layers of the yellow tape - great stuff. I threaded the elbow back off to check tha the tape was not bunching or slicing - it was intact and forming a nice seal.
I ended up trimming a couple inches of hose off to get back to undistorted hose and put it all back together. I won't be able to test it out until I pump out the little bit in the holding tank and flush it since I am in a river, but it is definitely better than it was.
Thanks for the input.
Joe