Sewer Drain Pipe Failure - grey water pipe disconnect

[txbanker123]

Coming back from a trip at Christmas, we stopped to make the final dump of the waste tanks. It was then I noticed the support bracket supporting the dump valve was snapped and the dump pipe was hanging just a bit lower than normal. Supported by the underbelly shield and foam insulation.

Dumped the black tank just fine (FORTUNATELY!)

Went to dump the grey water and noticed water draining out the passenger side and the underbelly was swelling a bit. Still getting water out the dump hose so I let it all drain. Took the rig back to the storage yard. Next weekend I removed all the screws securing the underbelly to the bottom of the rig. Dropped it down along with all the insulation which was soaking wet. All that is thrown out now.

On the passenger side, I discovered the issue. The drain pipe from the galley grey water tank had become separated from the reducer fitting in the 4" main sewer dump line. See photo below.

You can see the drain pipe from the grey water tank was inserted to the reducer coupling, but only about a quarter inch. Not glued. When the support at the opposite end broke, that enabled the pipe to move around just enough to allow the grey water tank pipe to pop free. I can push the assembly back up and get the grey water pipe to just fit inside the reducer coupling, but it will not hold.

So, now I am trying to repair and have a few questions for the board:
1. Why is the pipe not glued and what type of adhesive/sealant do I use when reconnecting the pipe?
2. Need to replace all the insulation. Will standard household insulation batts be fine - will remove the vapor barrier paper

I am thinking I will cut the grey water tank pipe and use a coupling to fit it back together. That should make the overall length a bit longer so it will rest inside the 4" pipe reducer more securely. Just wondering how to seal it back up.

This looks like Bad Design not Grand Design

Thank you for any suggestions
Don
2019 S310GK

[FT4NOW]

You might want to consider something like the rubber reducer below. It is designed for sewer pipes. I actually have 2 3" couplings on my sewer pipe from where I had to cut the pipe in 2 locations. No leaks and easy to take apart if needed. Not sure exactly on the small pipe size, I think 2", bit the large pipe should be 3", not 4".

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[WhittleBurner]

​The reducer suggested above would be the way we'd go. We had to replace the insulation due to a gray valve leak. We used Reflextix from Lowes, 2 rolls and some foil tape did the trick.

[powerscol]

For glue it is PVC cement, but get the black cement rated for your pipe. You will also need primer. Wear rubber gloves as it can get messy. You will first need to thoroughly clean the existing connection of the gray stuff I see in the pictures. You can use regular sand paper for this. You want o get back to the origination black pipe serface.

Hope this helps

[txbanker123]

Thanks for all the suggestions. I believe I have successfully completed the job. I also heard back from Grand Design who provided a couple of pointers. I did not need a reducer, but did use a 1.5" flexible coupling from Home Depot. I cut the pipe and used the fresh cut end to insert to the reducer on the sewer pipe end cap. Then I slipped the flexible coupler on.




The hardest part of the job was replacing the coroplast. So large and bulky! My wife suggested using a floor jack to aid in lifting it up the frame. What a great idea!



Really don't want to do that again, but I think we are back in business.