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Old 04-08-2023, 01:27 AM   #1
pohoda's Avatar
Brand: Thor Motor Coach
Model: Magnitude BH35
State: California
Posts: 61
THOR #23156
Fix: broken fitting on grey tank under kitchen sink with slide

We have been noticing a grey water tank smell in the galley and could not figure out where it was coming. Found out that the metal bracket that is meant to secure the ABS pipe elbow that connects to the grey tank fitting broke off. The most likely cause was an improperly installed bracket that came loose and the full slide then finished the job when moving in/out. I found the metal bracket with full fitting and spin weld tank adapter sitting in the slot in the slide and just leaking close to the opening in the grey tank which is likely why we never saw any water on the floor. It appears the kitchen sink water made its way to the tank opening, but of course it was open to expose the smell of the tank to the open air in the galley. I saw lots of discussions about this fitting, but nobody really put into detail how to repair this so I am sharing how I did it in case anyone else wants to tackle this.

Parts needed:
- rubber adapter to tap into grey tank and attach 1.5" ABS drain pipe to RV supply store had one in stock for similar price if you need it ASAP)
- Short piece of 1.5" ABS pipe (local hardware store of choice)
- 1.5" ABS pipe coupling (slip fitting)(local hardware store of choice)
- ABS glue (black) (local hardware store of choice)
- clear silicon (local hardware store of choice)
- plumbers tape (thin metal strip in a roll with holes in it)(local hardware store of choice)
- 1.25" wood screws (I used what I had which were corrosion resistant drywall style screws)(local hardware store of choice)
- 1.5" wood or drywall screws (used to reinforce frame for to support weight of drawers)(local hardware store of choice)

Tools needed:
- cordless drill motor with Philips driver
- Nut driver (1/4" iirc) or socket wrench with 1/4" socket
- Square drive bit
- razor knife
- Flat head screw driver
- 18"-24" bar clamps/spreaders
- First Aid kit ()
- lots of patience

The fitting that broke off is originally attached to the tank using a 2" spin weld fitting to 1.5" slip fitting. This type of fitting works great for creating a nice seal to the tank material, but is rigid and does not do well when exposed to lateral force. The way Thor designed this system is to run black sink drain pipe from the sink to rigid ABS pipe on the interior side of the coach wall and then attach a flexible hose in a U shape parallel to the floor to allow for flexing when the slide comes in and out. The flexible hose connects on the other side to the tank tap ABS that is on a 90 degree elbow with a metal bracket surrounding it to keep it in place and resist the lateral forces of the flexible hose being folded into a narrower U shape. I decided not to use a spin weld fitting for a couple reasons. 1) the original fitting broke and left residual pieces still welded to the tank. Getting those off with the little space available was going to be very challenging. 2) I opted to use a rubber grommet seal that allows for some flex and if exposed to any extreme lateral force will simply let loose and the ABS pipe will pull out of it without breaking (at least that is my thinking).

With the space available to access the tank you will need to remove the drawers (specific to BH35 yours may be different) and also the cross members (held on with 4 square drive wood screws) of the finished side of cabinet that separates the drawers from each other (divider if you will). Having the slide fully extended gives the best access to the tank opening and overall access. Once you have it opened up inspect the frame that holds the slide rails for the drawers and reinforce with wood screws (1.5" is what I used). I used 2 bar clamp/spreader bars to hold the frame in position and have it sit where it should so I could secure it into place. This thing just attaches on one side using the typical staples that don't hold well enough for this application. I added 5-6 screws to the existing frame mount and predrilled the hole to avoid splitting the wood. Then I added a plumbers tape strap to the right hand side that had no support and secured it to the plywood under the countertop using very short wood screws. Once this is secured you can move on to the repair of the drain. The above step is optional, but I highly recommend you fix this before it becomes a problem and falls apart onto the drain you are about to fix.

The first step is to install the rubber grommet into the tank opening. I can tell you that it may be possible to install this grommet in once piece, but I tried and eventually just cut it on one side to allow me to seat it into place. At one point I dropped the grommet into the grey tank and all I can say is . Luckily after I stopped seeing red and many failed attempts to fish it out I went to the wet bay and realized that the drain on the grey tank had a large 3" tap and after removing the fitting I was able to remove the grommet out of the valley of the tank with ease. Hopefully you will avoid this step and the frustration that follows. Apply the silicon sealant to the rubber grommet liberally as this will not only help seal it, but makes installing it much easier. It takes time, but within a few mins I was able to fully secure the grommet into the tank and then insert a short piece of 1.5" ABS into it (also applying lots of clear silicon to help lubricate it). You have to push pretty hard to get the 1.5" ABS to fully seat and when done it will go in about 2-2.5" inches. Just be careful not to push too hard as it will just slide all the way past the stop and into the grey tank. From here you can measure and cut the ABS to size to fit onto the original broken off piece. You will need to use a hacksaw or ABS pipe saw to cut off the old spin weld fitting and then when all is cut to size use the 1.5" ABS coupling with the black ABS glue to put it together. You will have to remove the elbow out of the metal enclosure to do this before installing it back into that for final assembly. Apply lots of the clear silicon around the grommet and anywhere you can reach. The elbow should be well under the bottom drawer so it clearly with a few inches space. Now reattach the flexible hose using the compression pitting and hand tighten. Position it so there is minimal tension and install the metal piece with 4 wood screws to the floor. Remember that this elbow and metal bracket also ends up being inside the black bag which is a royal pain to work around, but in the end it works out. Before reassembling anything let the silicon set overnight or 24H and test out the drain using a large bucket of water so you test the drain at full capacity. Check to make sure you have no leaks. Now test the slide for clearance by closing and observing how it tracks with the fitting in place. The fitting should remain where it is without being touched and the slide should mover with slot providing the clearance needed. The black bag will move as it is designed to isolate the whole area there and create a barrier between the outside and inside for critters and outside air. This is also you chance to see how the duct work and everything else is doing when the slide moved in and out and you can move stuff around to make it all clear the slide. If all is working as it should just secure the black bag by pulling the string and securing with the little spring clamp. Re-assemble the cabinet cross members and install the drawers.

In conclusion this was not a fun job, but waiting 3 months to get this into a shop or finding a mobile RV mechanic just wasn't happening soon enough for us. If you can wear long sleeves and gloves as you will get cut up (queue up FirstAid kit). I don't like wearing gloves because I need to feel what I am doing, but I did put on surgical gloves when working with the clear silicon. My arms and hands look like I got into a fight with a feral cat and lost. Hopefully most of you will only read this for amusement and not actually need to do this repair. Other than fixing the front cap this is the worst repair I have had to do yet, but I am certain it is fixed better than a typical repair place would do.
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