Porta-potty lower-tank pressure (due to elevation changes)

[Old Crow]

I'm probably not the only one to have gotten an unpleasant surprise when opening the slide valve on a Thetford porta-potty.

The lower tank is a sealed compartment so changes in elevation can cause pressure buildup inside the tank. Open the slide at the wrong time and distressing things will happen. Curse words will flow freely.

I mention this as I made a mistake last Fall.

After dumping and cleaning the potty, I added deodorant and water. Typically, I have the slide closed so I can use that little well above it to measure the deodorant. Then I add water and let the mix down into the tank.

This time, though, I opened the slide and put the water in and closed it to measure the deodorant. Somehow, I got distracted and forgot to let the deodorant down into the tank.

At this point I have to mention that I was also trying a new deodorant. It turns out that deodorant not only has a very strong smell but it also stains anything it touches a bright blue.

You can imagine where I'm going with this.

On the next toilet use, I slid out the toilet and -- thankfully--- thought to pull out the slide before opening the lid. That blew deodorant all over the toilet bowl and the inside of the lid. It even blew some of it past the edge of the lid. It looked like something out of a horror movie.

I grabbed paper towels and mopped up as fast as I could. I probably should have stepped away to let the air settle as my eyes were burning as I worked.

The worst part was the staining. That blue chemical somehow got into the plastic and just wouldn't come out for the longest time. I saw blue staining for days.

I shudder to think what would have happened if I would have opened the lid and seen the deodorant and had been over it as I opened the slide.

I added this to the potty lid to remind me to think whether the potty had changed elevation before opening the slide. But since the deodorant event, I always open the slide before opening the lid.

 

[RicoV]

Yep, real good advice. We had a similar experience early on with our Thetford, and it only took once to capture my full attention and quickly implement a protocol such as you've done. I sure hope you ultimately got rid of all the blue stains.
Rico.

 

[Wandering Sagebrush]

That can be nasty, in particular if you use something with formaldehyde in the formula. Having heard of folks putting the mix in the water reservoir, I always put the “anti stinkum” in the bottom tank, and water only in the top. Slowly opening the slide helps, too.

 

[Old Crow]

Yep, real good advice. We had a similar experience early on with our Thetford, and it only took once to capture my full attention and quickly implement a protocol such as you've done. I sure hope you ultimately got rid of all the blue stains.
Rico.

Yes, I was able to get them off once I took the toilet outside and liberally doused it with water while working at them with a micro-fleece rag. Cleaning sprays didn't seem to make a difference.

That can be nasty, in particular if you use something with formaldehyde in the formula. Having heard of folks putting the mix in the water reservoir, I always put the “anti stinkum” in the bottom tank, and water only in the top. Slowly opening the slide helps, too.

I've seen that idea of adding deodorant to the upper tank but also know the instructions for mine say never do that (and capitalize the 'never'). I'm not sure why. Perhaps some deodorants would stain the bowl.

In re-reading the instructions today, I see they also tell us not to put the deodorant directly on the slide (as I've been doing) for fear of damaging the seal. Perhaps that's the reason behind it.

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Also... for all...(on the topic of pressure in the lower tank)

I see there's an interesting post over on the Ford Transit USA Forum where a guy experimented with putting a valve in the cap of the drainage elbow to relieve tank pressure when elevation changes significantly. He installed a nylon valve from McMaster-Carr which opens at 0.5 psi pressure differential.

On his test he did a 3700-foot elevation change and found that the valve did eliminate the problem of pressure bowing out the sides of the tank and a possible seal rupture. However, it still left the tank 0.5 psi over-pressured. That still requires the slide to be pulled to avoid a surprise splash.