Community Forums

casper124 · 12-05-2013, 01:45 AM

Does anyone have experience in repairing the fresh water tank where the "T" connects to the bottom of the tank. I discovered a leak today in which the "T" was pulling out from the threaded entry of the tank. In checking the damage, I found that the threads on the "T" and the tank were stripped. Am considering trying to tap tank and try to re-install new "T". FYI the PEX coming from the tank and "T" leads to the Shur Flo pump and to the drain valve.

Thanks for any input

Steve

Old Scout · 12-05-2013, 08:48 AM

Sorry--no experience with repairing the tank but would think there are any number of sealants or bonding materials that would do the job. You could also drill out the existing opening and re-thread to 3/4 vs 1/2 inch [need the proper drill bit and tap]. As an alternative to drilling/tapping a new opening, I found a short-throw tee for the front dump pipe and moved the dump valve down below the tee. I then replumbed the pump feed line to the tee. This allows you to use "all" of the fresh water in the tank and you wont have to drill and thread a new hole in the tank. The challenge with trying to drill/thread a new opening is that the thickness of the tank walls are usually increased in the areas around the openings to provide strength and allow more material for cutting the threads.

casper124 · 12-05-2013, 04:11 PM

Thanks for info. Looking at tapping to see if it will work.

Old Scout · 12-05-2013, 05:11 PM

My bad--keep forgetting when WRV converted from a 1 1/2 inch drain tube and slide valve on the older coaches to a combination 1/2 inch pump feed and tank drain.

EngineerMike · 12-05-2013, 10:09 PM

I believe the 06 models still had the large drain w/pull-T-handle/cable blade valve for dump.
You can patch the tank plastic or the fitting plastic with schmutz of the Marinetex Flex Set epoxy type.

myredracer · 12-05-2013, 10:28 PM

If the tank's made of polyethylene, and I think they typically are, nothing will stick to it and only a mechanical fastener will work. I'm thinking re-tapping and new fitting may be the only option without replacing the tank. What about contacting one of the RV tank manufacturers and seeing if there is some sort of repair kit?

casper124 · 12-05-2013, 11:16 PM

The threads on the circular flange was in better condition than I first thought,so put in new T and appears to be holding,but, test will be loading water tonight. Thank you all for suggestions, always appreciated.

Steve

EngineerMike · 12-06-2013, 12:37 AM

Gil-
Looks like I botched the link; here it is again: Marinetex Flex Set epoxy
check the directions on the Marinetex link here; they specifically talk about polyethylene. I've used it before on poly-e w/out the heat treating to seal a fitting with great results, tho not on a full pressure seal, only a couple psi. RV tank might be 3psi at the outside under most conditions.

myredracer · 12-06-2013, 02:41 AM

Mike,

We'll I'll be! This is good to know.

The last time I researched this, I couldn't find any kind of exotic, space age or military grade adhesive whatsoever. This link mentions options and heat welding as one of them. Doesn't mention epoxy adhesive though. Polyethylene Adhesives and Glue - What are your choices...

This is a good video on the adhesive from another maker of the epoxy stuff. It seems like the epxoy has to be a very thin layer so it may not work where you need a buildup of material like in a messed up threaded hole?

How to repair and glue Polyethylene and Seaboard - YouTube

EngineerMike · 12-06-2013, 02:29 PM

The last patch I did on a poly tank was for a fitting in a 1/2" FPT tapped hole where the poly tank wall warped (had a thin spot) so the tapped threads were not right. I gooped it up to maybe a 1/8" fillet around the inserted fitting, and it held fine against maybe 10" of water column above it. I'm pretty sure it would work against a coupla feet of water column without the heat priming, but haven't tried it. The heat priming is surprisingly simple, tho in most cases in an Rv you'd have to take the tank out (or a buncha something else) to get at the repair area with the heat.

If patching a crack, I'd use an additional sheet of plastic over the repair for reinforcing. Usually if a crack starts on its own there is some residual stress in the base plastic due to initial manufacture or how the plastic item sets in use. If it cracked once there, it'll need more than glue spanning a crack to hold over time. Goop the crack, goop the exterior area around the crack, press the new reinforcing sheet over the exterior goop to remove air bubbles, & weight it into place till the glue hardens fully.

The Flex Set epoxy is surprisingly durable. I broke a plastic crank handle on a Black & Decker Workmate right where I'd expect it to break due to stress. Patched w/F.S. and it appears stronger now than when new, I can really bear down on it. The stuff actually takes days to cure beyond its soft stage where you can press a thumbnail impression into it. Instructions say earlier, but I like to give it 72hrs before a full structural load.