underbelly leaking possibly from grey or black tank

Check the hose that fills the fresh water tank. It is clamped on and the clamp might be loose at the tank end, so some of the water doesn't go in but goes down.

OK, a little update. DH cut the underbelly and looked like clear water and very little smell. So that's a good thing. Next he partially dropped the underbelly so now it's drying out and later today we are going to work on finding what the problem is. Since our freshwater is almost full. We figure to add water until it comes out of the overflow. Then see if any leaking occurs. We normally keep the fw only about 1/2 full. However we had to fill it a week or so ago because they are working on the roads and the water has been off for a day here and there. Just like today, it will be off all day. I'll give an update when we know more. Keep the ideas coming. They are VERY helpful!! Thanks so much!!!

Oh there would be no doubt if it were the black tank. Grey tank water will have a soapy dishpan smell. Pump will cycle if a leak in the freshwater system.

When you cut the coroplast make sure that the "hinge" of the flap is towards the front of the unit. That way the underway wind will keep it closed as opposed to ripping it open over and over.

You have an odour. Can't mistake black for grey with a smell test.

The 5er we had suffered a partially dropped fresh water tank that made the underbelly swell down. The fresh water tank is made of a plastic that can swell, but the black and grey tanks are stiff.

First cut the underbelly low point and let any water out--collect some in a bucket for a better smell test. As said, black Gorilla Tape works to repair the cut.

I am thinking just a water leak won't make the underbelly swell down, but first drain it. Ours never went back up flat in shape after the tank dropping episode.

The soaking wet pink insulation is a write off, ignore it. Probably didn't do any good anyway.

the age man gave you the way to go.

I assume you would know if it was black. Either way you need access.

Assuming tank is black ABS plastic I recommend Plasti-Mend to make the repair. Amazon or buy direct. If the crack is large plasti-mend has sheet ABS to reinforce the repair.

Good luck doing this on the road. Maybe some eternabond tape could make a temporary repair.

We had something similar. Found a crack in fresh water tank (glad is wasn't black tank). We replaced tank and insulation, then put the coreplast back on.

You could put some dye in one tank or the other to localize the leak. Probably the gray tank. Maybe food dye would do it. Then you'll have to cut a flap in the coreplast and do a temp patch on the leak with eternabond if you have any. Close the flap up with gorilla tape. You may have to pull out wet insulation. Get some rubber gloves.