This doesn't look good....sagging floor?

[rickst29]

If you have a cassette toilet, you should temporarily remove it and verify that it does not leak clean water content onto the floor in a test area.

You have only a gray tank, with no separate dump valve for a Thetford or a poor man's Sealand. There is a chance that "gray water" continues to leak from bad drainage plumbing for the kitchen or bath sinks, but it is mot likely a problem with the tub drain.

(A pierced or cracked "fresh" line could also be responsible, inclduing the possibility of the outdoor shower lines - if they were ever allowed to freeze with water in them.) But I would suspect the tub drain first.

My own TM bathtub is failed in some manner, and not yet fixed. On a recent trip, we over-filled the gray tank while washing dishes on the last day. I had expected that it would rise into the tub, WITHOUT LEAKING, allowing us to dump later - but it instead began leaking into the floor, very slowly, and dripping to the ground from there. I had to dump the excess at the campsite, into a different container, to stop that drip.

If your bathtub has ever been used as a bathtub (rather than a shower pan), a similar leak might be present: From hairline cracks in the lower tub, or (more likey) from a failure in the drains' connection into the gray tank. In my temporary case, the leakage probably occurs from the tub drain when the drain is filled and unable to drain into a tank without "adequate room" for the drain to clear quickly.

A filled tub, even with room available in thee tank, would have standing water keeping the drain pipe full for a considerable time when you begin to drain the tub.