Overflowing Dometic CT 4000 Toilet

Sparkster · Senior Member

Overflowing Dometic CT 4000 Toilet

Possum3 · Guru

It happened to us once this year - problem was the blade didn't close properly - only the once and never did it again. Check that your blade and mechanism is working correctly.

Baz421 · Guru

Sparkster wrote:
Yep! The subject heading says it all -well mostly.
For some crazy reason our Dometic toilet has started overflowing the waste tank onto the floor of the van leaving a rather smelly mess when we reach our destination.
The tank need not be even as high as half full or even on rough road to overflow.
The main "O" ring was replaced by a Dometic Agent but made no difference.
Has anybody else had this problem and found a cure?

Don't have your model, but suggest you do a practical check of all seals (obviously) and see where leak is.

To do this get a garden hose turned on SLOWLY and stuff a rag in the outlet and SLOWLY fill with water, you should then see what is leaking, ie breather valve , main seal or vent for discharging. I think this is the only 3 ways it can leak to the floor area.

Also be aware "slop" in tanks etc is often worse with 1/4 to 1/2 full range. We had to modify water tankers years ago with baffles as they "fell over" when less than 1/2 full quite often.

Sparkster · Senior Member

Thanks Possum the slide is definitely firmly home when it happens.

Baz this model takes water from the 'van water supply so I can probably rig something to pressure test the seals etc.

I've tried a few things while on the road and one of the conclusions I'm sort of thinking about is that there is a build up of pressure in the cassette and along with the sloshing around the liquid forces its way out through the seals.

So along with your suggestion I'm going to pay particular attention to the 'pressure relief system', making sure that some groobly hasn't made its home in the vent tubing.

The system gave us no trouble for 1000's of Km's then bingo, smelly water everywhere - nice!

greyhoundtom · Senior Member

Sometimes a change of chemicals combined with warmer weather can certainly increase pressure inside the tank, or even just warmer weather on its own can do the trick.

Therefore plain water tests may not find the cause of the leak.

There again I did strike minor problems in this regard and not being prepared to fiddle too much with a soiled tank I dumped the tank and just bought a new one, which in my case solved the problem.

Cheers, Tom

Sparkster · Senior Member

Thanks greyhoundtom, the thought of replacing the tank had not yet occurred to me mainly because I can't see how the tank would be the cause.

My reason for that is that is that it doesn't appear to do it when standing still.

Then again the argument against my thoughts there could be flexing of the tank while the vehicle is moving.

What's a new tank worth?

What about if I half filled it with soda water and shook like b****ry? Not kidding!

But the first thing will be pressure testing the whole system as suggested by Baz.

-- Edited by Sparkster on Monday 5th of October 2015 08:18:16 PM

-- Edited by Sparkster on Monday 5th of October 2015 08:33:47 PM

Baz421 · Guru

Sparkster wrote:

Baz this model takes water from the 'van water supply so I can probably rig something to pressure test the seals etc.

What I suggested will be a basic test of the tank only independent of the supply. IF you find nothing then I would look to supply (overpressure) or some other issue???? Confirm it is not hooked up to the van's water pump as that is a no no for those models I think.

Good idea to clean pressure relief valve if crap has sloshed around -agree.

Sparkster · Senior Member

Sorry Baz I was thinking aloud a bit as I can't get to mains water. We live in a retirement village and the 'van is parked with other 'vans in a compound.

While travelling I have turned all water supply to the unit off to eliminate incoming pressure problems.

The Dometic unit does not have its own tank and is only supplied from the 'van, be it pump or mains.

Tomorrow I think I'll be addressing the pressure relief system first. The valve that sits on top of the tank has had a good clean out today.

Baz421 · Guru

Sparkster wrote:
Sorry Baz I was thinking aloud a bit as I can't get to mains water. We live in a retirement village and the 'van is parked with other 'vans in a compound.
While travelling I have turned all water supply to the unit off to eliminate incoming pressure problems.
The Dometic unit does not have its own tank and is only supplied from the 'van, be it pump or mains.
Tomorrow I think I'll be addressing the pressure relief system first. The valve that sits on top of the tank has had a good clean out today.

Are you sure it's a CT4000 or a CTS4110???? If the 4110 and you can't find anything with your tests make sure the toilet pump is not running without pressing the button ie a loose wire etc.

Here's some links to parts and manual if you don't have them.

https://www.getawaeco.com.au/files/CTS4110_AUS_NZ.pdf

http://caravansplus.com.au/catalog/product_info.php?products_id=12067

http://caravansplus.com.au/catalog/pdf.php?pdf_id=857

Sparkster · Senior Member

Thanks Baz, the paperwork I have with the supply of the 'van gives the model number so first thing tomorrow I will check the name plate on the unit.

I guess what is possible is that it could be a 4000 series.

Shall check tomorrow.

banjo · Senior Member

It will more than likely be the pressure release valve jammed, it is on the top RH of the cassette and seats into a spring loaded device in the housing.

Ours did similar,a quick spray of silicon cured it for us, but having said that we have had many other issues with leaks and seals from these toilets, would never have another dometic one, simply expensive rubbish.
We had a Thetford in all of our other vans and never any problems.

Hey Jim · Guru

Hi Sparkser,

You could try using a dye bomb ( from plumbers supplies) in the tank with half full of fresh water. And go around the block a few times. You may find a hair line crack in the Tank perhaps. confuse confuse

Regards Jim

greyhoundtom · Senior Member

Sparkster wrote:
Thanks greyhoundtom, the thought of replacing the tank had not yet occurred to me mainly because I can't see how the tank would be the cause.
My reason for that is that is that it doesn't appear to do it when standing still.
Then again the argument against my thoughts there could be flexing of the tank while the vehicle is moving.
What's a new tank worth?
What about if I half filled it with soda water and shook like b****ry? Not kidding!
But the first thing will be pressure testing the whole system as suggested by Baz.

-- Edited by Sparkster on Monday 5th of October 2015 08:18:16 PM

-- Edited by Sparkster on Monday 5th of October 2015 08:33:47 PM

I certainly do hope you can fix it out by simply replacing a seal somewhere because a new cassette will cost around $350.

Cheers, Tom

Sparkster · Senior Member

The Model # is 4110, my apologies the 4000 is a series of models evidently. The paperwork reads 4000.

Can confirm there are no grooblies living in the pressre relief tube.

Removed the only remaining (large) "O" ring seal could not see any evidence of leaking and applied silicone to all seals.

I have previously partly and fully filled the tank and left it in the heat of the day and shaken it but no evidence of leaks.

I agree with Banjo re; the quality, I've had several Thetfords over the years with absolutely no problems and they had covered a lot more K's and rattly roads than this Dometic.

I like the sound of the dye bomb idea. We're off on a short 1000k trip next week with varying types of roads so if all the seals and valves cleaned and lubricated doesn't fix it the bombs the go.

Thaks so far for ALL the ideas, I have used or will be using them in some way.

Sparkster · Senior Member

Well I've reassembled the offending Dometic cassette and put some low pressure air pressure through the vent pipe and detected no leaks so fingers crossed.

At least the valve worked which was where I had doubts.

It'll get a test this coming week.

I'll post how it went.

banjo · Senior Member

As a follow up to these ****ty toilets (excuse the pun), we have been parked on a slight slope side to side, as we have been block sitting for a couple of weeks over the dreaded school holidays, even on blocks the door side is still low.
We have compressor fridge so no worries there, but noticed the front of the toilet where the slide exits has leaked onto the floor ! must be the slight pool of flush water left sitting on the blade that has found it's way past the seal yet again.

These Dometic toilets are a disaster for full time use, maybe ok for occasional use, but not designed at all for longevity.

In 3 years ours has had a new cassette, a new slide mechanism, two new seals all under warranty, and is on it's last orders as far as I'm concerned.

greyhoundtom · Senior Member

Well that's been burned into my brain "Never buy a van with a Dometic toilet system".

Thanks for the update.

Cheers, Tom