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turboeclipse · 10-31-2022, 04:15 PM

I have been struggling with this for a couple of years now. Standard thetford toilet. Always leaking from the universal coupling to the plastic water pipe. I replaced the coupling...still leaks. Used plumbing tape on all threads. Still leaks. It seems any side to side torque on the fitting will cause it to leak. Unfortunately the pipe coming through the floor has a slight offset to the toilet so this is enough to cause it to leak. The plastic compression fitting to the water pipe seems questionable. It isn't really a true compression type fitting. It just screws over the pipe which is press fit onto the nipple. Seems like a kludge to me. Has anyone come up with an alternative using more secure type plumbing fittings? Maybe using a flex hose?

Capacitor · 10-31-2022, 05:43 PM

Is the plastic pipe you mentioned PEX? Can you post a picture?

THenne1713 · 10-31-2022, 10:49 PM

The plastic screw-on fittings used w/ PEX use a RUBBER WASHER and hand pressure to tighten... THREE CAUTIONS: 1) DO NOT USE pliers/ wrench to tighten, they CRACK; 2) IF INSTALLING new fitting to PEX, either use SHARK-BITE PUSH-ON, or PEX crimp; (screw-type hose clamps WILL LEAK on PEX, but are OK on the softer, braided, reinforced HOSE); 3) ALWAYS Use PRESSURE REGULATOR.

ON YOUR TOILET, suspicion is that TOILET VALVE PLASTIC IS CRACKED, (if PEX fitting is good?) GOOD LUCK.

turboeclipse · 11-01-2022, 07:54 AM

The RV is a 1997 so it predates PEX. None of the PEX fittings fit the existing plumbing. The outside diameter is the same but PEX has a much thicker wall. I learned that the hard way when replacing a bunch of it after a winter freeze issue. PEX will not even fit on this coupling. Its the coupling itself that leaks even though it is brand new.

THenne1713 · 11-01-2022, 10:39 PM

YOUR FLOOR PIPE LOOKS LIKE COPPER? If so, the SHARKBITE PUSHON series can adapt you to braid hose, or PEX, or whatever you need? What is the toilet connection size/style?

While many pipe fitting THREADS are tapered, plastics are not, as they would crack, and so seal is ORING OR RUBBER WASHER, sometimes flare SEAT.

THenne1713 · 11-02-2022, 12:16 AM

"Pretty sure" (from your pics) your fitting is wrong, and designed for soft braid reinforced hose, similar to 1/2"-RV/Marine white hose.... which is why it doesn't work. Is the toilet end a 3/8" OD plastic/pex/vinyl tubing. or what?

OTHERWISE, MAYBE HIS WOULD HELP w/ the FLAIRIT fitting connection to piping?

https://www.youtube.com/watch?v=yv2EEesxZEo

turboeclipse · 11-02-2022, 08:18 AM

Not copper. The sharkbite fittings don't work with this piping. I spent many hours at Home Depot/Lowes trying to find a solution when I had to replace some the original piping with PEX. I had to go with some non standard fittings and do the heat trick with some screw clamps to get a reliable connection. So far 2 years with no leaks. The piping is plastic and original. The toilet end is 1/2 inch OD same as sprinkler system fittings. What you said explains a lot. I had the toilet replaced by a supposed RV repair guy about 15 years ago. I don't remember how it was originally connected. The leaking issue showed up when the plastic pipe eventually worked it way out of the fitting due to vibration. It was definitely a kludge setup. So it looks as though the coupling is all wrong for this type of plastic pipe. The new coupling is identical to the one that was in there. I was told this was the correct coupling for my RV and toilet. Thanks for all the suggestions.

luvlabs · 11-02-2022, 08:29 AM

You are missing the white plastic compression ring. This type of fitting is very similar to a copper compression fitting (the ones that use a brass ring around the tubing). Get yourself a whole new fitting at your favorite big box store and start over.

Steve-W · 11-02-2022, 09:00 AM

The gray pipe is Polybutylene. here is a link to many different fittings. You should be able to find something here or at other suppliers that will work for your application. Make sure the end of the pipe stub is not deformed or otherwise compromised, if so you may not be able to obtain a leek free connection.

turboeclipse · 11-02-2022, 05:00 PM

That coupling did not come with a compression ring. It isn't tapered so I don't see how that would work. As mentioned previously I think its designed to work with flex hose. I came up with a solution. Plastic 1/2" barb. Use white 1/2" flexible hose to toilet coupling. Barb to other end of 1/2" flexible hose...other barb to plastic hose. Hose clamps on both sides of barb. Works like a champ. Thanks for all the suggestions!

THenne1713 · 11-03-2022, 02:47 PM

Polybutylene was often used in MOBILE HOMES in 60s/70s, and outlawed for residential after push-on fitting failures started causing flood events after aging?