I've had a bad smell in the bathroom for weeks. Kept sanitizing both black and grey tanks, dumping them, plugging drains, checking vents,
having a jolly old time. Today I pulled off the toilet, found absolutely no smell coming from the black water tank, but also found the problem.
The problem is the defective Dometic 300 toilet itself. The toilet is composed of numerous pieces, and two of those pieces assemble together with two gaskets at the joint. Well these gaskets somehow allow urine to pass through, and it builds up inside the toilet body. This is all explained very well in
this unnecessarily long video. It's a simple DIY fix, but a frustrating one to have to do.
In my case, I brought the toilet outside the trailer and can clearly see up to an INCH of standing urine inside the toilet body. Well that sure explains the stink!
Before proceeding with the DIY fix, I called Dometic to chat about warranty. This trailer is less than 9 months since new, and has probably around 20 nights camping in it.
The guy on the other end wasn't the least bit surprised to hear what I described, he probably takes these calls every day. He quickly offered to send a replacement 300 toilet, but after I inquired about upgrading to the 310 (much better model), confirmed that it's an option for an extra $75 USD fee. No-brainer, as that 310 is porcelain (vs. my super squeaky plastic 300), has a soft-close lid, and a design that does not suffer from the problem I'm dealing with. (Which would develop again on the replacement 300.) The cheapest option to buy a 310 is $400 CAD + tax, so this warranty-exchange gets me the same toilet for less than a quarter of the price.
Fired off all necessary info to Dometic's email, now the wait begins.
While I was down there, I also added an inline shut-off valve for the toilet's water hose. Typical, corner cutting Winnebago couldn't be bothered to install one at the factory.
They also overtightened the base plate, resulting in numerous cracks in the plastic, and a piece of it missing entirely. Yeah...