Waste Water Tank, pipes and slow draining sink.. (1 Viewer)

[Paul and Fiona W]

We're new to MH'ing, having bought our first one only two weeks ago.

On our second trip out last weekend, the smell from the toilet/shower room was indescribable (well, I work for a specialist drainage company, so I can describe it), but it was enough to make Mrs W gag. We discovered that the smell was due to septic water in the waste water tank, but why would the smell pass into the cabin if the pipes from the shower and hand-basin pass below the chassis rail before entering the tank effectively forming a trap ?

I disconnected the drain tap (it was blocked with slimy stinking goo), and back-flushed it by pushing my garden hose up... the result was that any blockage was pushed back into the tank, allowing about 40 litres of putrid water to empty onto my drive !! I had poured half a bottle of bleach into all the plugholes so the smell wasn't as bad as it might have been......

So, my questions are:-

Is it normal for the corrugated waste pipes to pass below the chassis rail before going into the top of the tank or is this a lash-up by any previous owners?

Can I use Mr Muscle or similar in the plugholes to remove any scaling/slime that may be reducing the flow and keep them clean?

Can I use ordinary house-hold bleach without risk to the pipes/fittings ?

Are there any techniques/products I should be looking for ?

Cheers

Paul Walters..

 

[pappajohn]

Hi Paul and welcome.
Bleach can have an adverse effect on the rubber seals.
You will NEVER get rid of the smell.
Buy 1/2 dozen bottles of cheap cola...Aldi own etc...then tip into the tank via plugholes, go for a vigorous drive to 'stir' the cola, leave a couple of hours then drain down again.
Has the effect of cleaning the tank of sludge and slime.
Fit sink plugs and cover shower drain when not being used, it will contain any stink.

 

[Paul and Fiona W]

I'd heard of the cola thing... used it to clean coins in the past, so it must have some "dissolving powers"... Aldi here I come !!

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[MC 55 FUN]

I'd heard of the cola thing... used it to clean coins in the past, so it must have some "dissolving powers"... Aldi here I come !!

Buy the full fat, all dissolving stuff, not the diet version

 

[peterc10]

Drooping drain pipes are a sign of poor design. They are not normal but are not uncommon I am afraid. As you have found out they are prone to smelly blockages if not regularly flushed through.

Our motorhome has a double floor that takes all the services so no drooping pipes.

 

[Spanda]

Ours thankfully has straight pipes and local traps in the shower and sink so any smell doesn't come back into the habitation area. None of which is any help to you ! What we have found is that, even though we have effective traps, the movement of the van when we are driving can shift the water from the traps and down the waste pipe. When we park up one of our check list jobs is to run a small amount of water down the sink and the shower room drain to make sure the traps are effective. Filling the droopy pipes that way would help, but if your DIY skills are up to it, and there is room to fit them, I would suggest putting traps immediately on the outlet from the sink and the shower to make sure you don't get a smell from gunge adhering to the inside corrugations of the pipes.

As others have said, avoid bleach at all costs.

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[Shrimp]

We've used washing soda in the past to clean the wate tank, dissolve well in hot water, let it sit in the tank, go for a drive, drain tank. It does help but we've also used the 'proper' stuff, I don't think anything-short of a new tank-will ever be 100%! The concertina pipes don't help! I also find that if the van is really level the sink is slow to drain, it likes a bit of lean to one side!!!! Hicccc!!!!

 

[pappajohn]

Another trick, if you can access the large inspection bung, around 4" to 6" wide, on the tank.
Tip in a bag or two of ice cubes then pick a route with loads of tight corners.
The ice will dislodge any crud before it melts then flush out the tank.

 

[Paul and Fiona W]

From what I can see underneath the vehicle, the x3 shower outlets, plus the hand basin are connected into x2 inlets into the tank. There is a real spaghetti of corrugated pipes and 90deg bends and T couplers joining them all together so that 3 of the 4 of them form U bends under the chassis rail before entering the tank in 2 ports alongside each other. As an engineer working in the waste water industry, I was appalled to see such lack of hydraulic efficiency, with such potential for blockage. That's why I wondered if it was a lash up.....

On another note, would anyone have expected the motorhome centre we bought it from (and who did a full pre-collection habitation check) to have emptied and flushed the tank out for the sale ?

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[Two on Tour]

Check that you have water traps on each sink, shower and basin drain otherwise there's nothing stopping the pong directly coming from the grey tank.
As your driving along the bumping and bouncing will make the tank expel it's bad breath. As @pappajohn suggests, we always travel with plugs in plugholes.

 

[MC 55 FUN]

On another note, would anyone have expected the motorhome centre we bought it from (and who did a full pre-collection habitation check) to have emptied and flushed the tank out for the sale ?

Err . . . yes we would & both our purchases had this done - however there are dealers & there are . . . . err . . dealers

 

[Riverbankannie]

Err . . . yes we would & both our purchases had this done - however there are dealers & there are . . . . err . . dealers

Ditto

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[Riverbankannie]

From what I can see underneath the vehicle, the x3 shower outlets, plus the hand basin are connected into x2 inlets into the tank. There is a real spaghetti of corrugated pipes and 90deg bends and T couplers joining them all together so that 3 of the 4 of them form U bends under the chassis rail before entering the tank in 2 ports alongside each other. As an engineer working in the waste water industry, I was appalled to see such lack of hydraulic efficiency, with such potential for blockage. That's why I wondered if it was a lash up.....

On another note, would anyone have expected the motorhome centre we bought it from (and who did a full pre-collection habitation check) to have emptied and flushed the tank out for the sale ?

And Welcome to the world of MH builders

 

[MC 55 FUN]

To prevent your grey waste tank filling up simply drive around with the . . . . .

 

[tonyidle]

It's worth changing all corrugated pipes for the flexible smooth bore type. Corrugations slow the flow dramatically and trap crud.