# proper Flush toilet in motorhome



## jph6969 (Sep 22, 2012)

Hi all, my first post inthese forums! 

After much research I have bought a 12m coach and am converting it to a motorhome. I've moved some of the misted windows around and stripped the insides completely and am in the process of planning the layout of the inside including shower and toilet and have a couple of questions. 

1) I am planning a 'normal' toilet with cistern and U bend like in a house. has anyone got any experience of doing the same and any pitfalls or tips. 

2) is there any reason my gray water cannot be put in the same tank as the black water? 

Looking forward to your replies!!


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## cabby (May 14, 2005)

a domestic toilet will use too much water.not sure if there size of pipe work will match up to the black tank.
The reason there is a grey tank and a black tank, draing black tank, then empty grey tank trough the black to flush it out.

cabby


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## gaspode (May 9, 2005)

jph6969 said:


> 1) I am planning a 'normal' toilet with cistern and U bend like in a house. has anyone got any experience of doing the same and any pitfalls or tips.


I would imagine that the first time you brake sharply or take a tight corner the water in the U bend will go straight into the holding tank leaving the tank contents open to stink out the whole coach. Also domestic type cisterns would use far too much water (you'll soon realise that in a M/H fresh water is a resource you don't waste) and they'll leak their contents onto the floor at the same time your U bend empties into the holding tank. You need to use either a cassette toilet or a marine toilet if you intend using a fixed holding tank.



jph6969 said:


> 2) is there any reason my gray water cannot be put in the same tank as the black water?


Grey water is easy to dispose of, black water less so. As soon as you put any black waste into your grey tank the whole lot becomes "black" making disposal more difficult. You use seperate tanks and rinse the black tank with the contents of the grey tank. Also if your sink/shower empty into a tank containing black waste the smell will percolate back through the waste traps due to the same reasons stated above for the toilet.


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## nicholsong (May 26, 2009)

jph6969 said:


> Hi all, my first post inthese forums!
> 
> After much research I have bought a 12m coach and am converting it to a motorhome. I've moved some of the misted windows around and stripped the insides completely and am in the process of planning the layout of the inside including shower and toilet and have a couple of questions.
> 
> ...


Gaspode has given you very good reasons why not. I should just forget the flush toilet idea.

It sounds as though you may be wanting a lot more advice in future - all readily available from members on here, but you will need to subscribe after 4 more posts.

Geoff


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## jph6969 (Sep 22, 2012)

> I would imagine that the first time you brake sharply or take a tight corner the water in the U bend will go straight into the holding tank leaving the tank contents open to stink out the whole coach. Also domestic type cisterns would use far too much water (you'll soon realise that in a M/H fresh water is a resource you don't waste) and they'll leak their contents onto the floor at the same time your U bend empties into the holding tank. You need to use either a cassette toilet or a marine toilet if you intend using a fixed holding tank.


thanks for that gaspode, the water usage is not really a problem as the coach has a huge boot into which I plan to put a 500L water tank, and the black/grey water tank. The water in the U bend is another issue I hadn't thought of though. Really want the comfort of a proper bathroom so will have to come up with a solution a couple of things come to mind

1) dry flush the toilet so that the cistern doesn't refill 
2) fit some sort of bung in the toilet for during transportation 
3) fit some sort of one way/shutoff valve in the black waste pipe that stops fluid/ air comming back up the pipe.



> Grey water is easy to dispose of, black water less so. As soon as you put any black waste into your grey tank the whole lot becomes "black" making disposal more difficult. You use seperate tanks and rinse the black tank with the contents of the grey tank. Also if your sink/shower empty into a tank containing black waste the smell will percolate back through the waste traps due to the same reasons stated above for the toilet.


I realise that the black water is more difficult to get rid of, one of the reasons for going for such a large waste tank as I wouldn't have to empty it so often. I have thought about putting a couple of disposal mechanisms in

1) a dump valve that I can connect a dump hose to if there is the facility to do so 
2) dumping through a macerator pump into a portable waste tank for disposal in the same manner as a cassette.

Having a separate grey water tank with pump will mean that I don't have to empty the black tank as much. Thanks for those points.

Thanks for letting me know about the post limit I shall have a look at the membership.


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## pippin (Nov 15, 2007)

500litres of fresh water isn't going to last that long if you intend flushing toilets with it.

Experiment at home, measure water usage per flush and per shower. Then do the maths.

Your suggestion 
_2) fit some sort of bung in the toilet for during transportation _

I wouldn't fancy that little operation, handling/storing a sh1t covered bung!

I suspect that what is important to you is being able to s(h)it on a proper-sized porcelain bog.

A marine toilet will fit the bill if you are that desperate.

Take note of Gaspode - he has a wealth of experience.

PS While you are at it, why not fit a bath, washing machine, dish-washer, tumble-drier.............
Although obviously meant in jest, if you want all the comforts of home.........


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## gaspode (May 9, 2005)

jph6969 said:


> 2) fit some sort of bung in the toilet for during transportation
> 3) fit some sort of one way/shutoff valve in the black waste pipe that stops fluid/ air comming back up the pipe.


What you describe is a marine toilet, go get one and stop trying to re-invent the wheel.

Water and waste tanks of 500 litres each sound rather OTT to me, have you considered the possible effect on the handling of the vehicle? I'm not an expert on RVs, you need to talk to an RV expert as the waste tank arrangements you propose sound to me as if they're just normal RV practice. On "normal" M/Hs best practice is to carry as little waste as is practical, why lug around half a ton of waste for days on end when you can simply empty it? In UK and Europe it's usually easier to dump small quantities of black waste than it is to dump large amounts.


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## bigcats30 (Aug 13, 2012)

1 litre of water weighs in at 1kg

even a bus only has a limit to what it can carry.


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## pippin (Nov 15, 2007)

Do the maths again.

500litres of fresh, 500litres of grey/black - that's a *tonne* of liquid sloshing around!


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## nicholsong (May 26, 2009)

pippin said:


> Do the maths again.
> 
> 500litres of fresh, 500litres of grey/black - that's a *tonne* of liquid sloshing around!


I agree that 500lt is stupid - particularly if most of it will 'go down the pan',

However, none of us have the fresh and waste tanks full at the same time. If we start a trip with waste tank/cassette empty and fresh full(say 150lt) we will still only have 150lt on board, whichever tank it is in - unless we top-up fresh before we empty waste. If waste is full there is no point in putting in more fresh, except for tea/coffee etc.

Geoff


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## ceejayt (Nov 25, 2005)

Just as a guide - we carry 370 litres of fresh and a waste tank of 165 litres - we opted for having two cassettes for the toilet so we can swap out. Dometic do an excellent porcelain bowl and toilet seat set up so no need to 'splash out'  on a real toilet.

With this set up we are good for at least 7 days without worrying about anything and more sparingly 10 days. Cassettes are so much easier to deal with than trying to find somewhere to empty a big black tank. We considered a marine toilet and black tank but glad we didn't.

Hope that helps


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