Our Grey Water Mystery Leak

Shortly after we moved in, we started noticing water on the ground under the dump valve for the black tank and one of the gray tanks. Thankfully, the water appeared to be either fresh water or gray water! But it was a concern and needed fixing.

Our unit has an all-weather sealed underbelly, so the water leaking could have been coming from any number of places and traveling along the underbelly to the drain valve area. We were really concerned, because water can do a lot of damage when the leaks are not addressed quickly. During the course of troubleshooting, we noticed the leak was the worst when the bathroom gray tank was close to full.

A view of the dump valve and waste drain area

I made a small incision in the corrugated plastic liner covering the underbelly to dry it out and get a better look at the problem. I could see the bottom of the gray tank, but it still wasn’t clear where the water was coming from.

I moved indoors and opened the two access panels in the bathroom, one under the shower and another under the sink. Under the sink, I opened the lower access panel in the sink cabinet and found a large space with the water feed, the drain plumbing, and several electrical lines. (The lighter colored boards in the floor area of the lower cabinet were added for another project I started shortly after fixing the leak. Stay tuned for a future post about that.)

An open cabinet with access panel removed

The black sink drain pipe ran straight down through an opening in the floor and directly into the top of the grey tank. I got a nice look at this area when the tank was full and there was no indication of water leaking in this area. The water in the park tends to be hard so a chalky residue would have been present if there was a history of leaks in that area.

The shower also has a drain that leads to the grey tank that is accessible through a second small access panel under the shower drain pan.

Sn open access panel for the shower pan

When I pulled this panel off the cutout area behind it was barely large enough for my arm. I wanted to get a better look so I used my cell phone camera as a periscope to see what there was to see.

When I first moved the phone into the opening a very frightening picture appeared: a large hairy spider appeared on the screen that appeared to be the size of a dinner plate! Once I adjusted the zoom on the camera, I realized we were not being invaded by giant spiders. After recovering my dignity and rehoming the tiny arachnid who was as surprised by the intrusion as I was, I tried again.

My arm barely fit in the access hole, so I used a razor knife to open things up and dull the sharp edges. I was able to fit one arm and my phone in the space so I used the video option to view the areas under the shower pan. (I was not very excited about sticking my arm and phone into an area where there may be more spiders but tracking down the leak was important.)

It took several attempts, but I was able to get a decent view of the drain and saw that it went straight down from the shower pan and took a 90-degree turn just below the floor. I could not see where it entered the grey tank. To check the area I could see I started running water in the shower and monitored the area for leaks. Very quickly, I saw water dripping from the connection to the shower pan. That connection used a friction-fit coupling and a large plastic threaded nut to secure the drain line into the shower pan.

It took some contorting, but I was able to reach far enough to get a hand on the nut— which was very loose. The loose nut caused the shower drain pan joint to leak directly into the space below the floor and drained out the lowest point by the dump valves. Of all of the problems that could have caused the leak this had to be the best problem to have, the water leaking was soapy shower water. I was able to tighten the nut enough to stop the leak. I suspect it was not properly installed at the factory. I have heard of issues like this coming up from time to time.

a view inside the shower drain pan area

Success! We haven’t seen any leaks since.

This issue could’ve been a major problem requiring expensive and invasive repairs. We are grateful that this was such a quick fix!

Published on July 4, 2019. Last modified on July 7, 2019.

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