Shower Enclosure - will it drain correctly?

[rarara]

Hi, I'm hoping that someone can give me some advice on this issue:

Just moved into a new place and there is no shower, so will add one to the corner of the bathroom opposite the current bath. At the moment the bath/sink etc feed into a vertical cast iron soil pipe which is boxed in against a wall (its a Glasgow tenement flat, so an unusual arrangement). The bottom of the inlet to this where the bath/sink feed is about 4cm above the level of the floorboards, but hidden by the sink vanity unit.

I am proposing to join the shower waste to where the bath waste goes, so maybe entering it at a height of 6 or 7 cm. I realise that the drain of the shower will need to be higher than this level, so raising the enclosure shouldn't be a problem but here is the issue:

To get the shower waste across to join up with the rest it needs to horizontally cross the room, so will therefore need to be under (or at the very least level) with the floorboards. It will have to travel 1.5m and then have a right angle and travel a further 1m. Lets assume the base of the enclosure is 15cm, and the point it connects to the other drain is 6 cm, that means there is a *TOTAL* fall of 9cm in 2.5 metres = OK! BUT, since the base of the pipe could be 4cm from the top of the boards, it will then have to rise say 10cm right at the end to allow it to exit. Will this:

A) be a problem with draining quickly enough from the shower, since the step up needs to be overcome? I don't want to be standing in an inch of water every morning in the shower.

B) assuming a) isn't a factor, will there be a constant 2.5m of standing water in the pipe between taking showers? Is this a problem? Or will the water be sooked out by the action of entering the soil pipe?

I am trying to get my head around resolving this! I have considered such things as hepvo's and pumps but am not sure if they will be of value. Downstairs have the shower in the same location, so it must be possible

Hopefully my description of the problem isn't too confusing!

Thanks

 

[Richard C]

since the base of the pipe could be 4cm from the top of the boards, it will then have to rise say 10cm right at the end to allow it to exit. Will this:

A) be a problem with draining quickly enough from the shower, since the step up needs to be overcome? I don't want to be standing in an inch of water every morning in the shower.

No you cant do that & yes, it’s a serious problem ; water doesn’t flow uphill very well. The whole waste run will be constantly full of water which is not only against Building Regulations, is also a health hazard.

B) assuming a) isn't a factor, will there be a constant 2.5m of standing water in the pipe between taking showers? Is this a problem? Or will the water be sooked out by the action of entering the soil pipe?

As above, it is a serious problem. There are Building Regulations covering both the length, size & connection of waste runs;
http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADH_2002.pdf

It’s also best practice to have a separate connection into the stack for each appliance or you will almost certainly have problems with trap siphoning; but probably not with the shower

 

[rarara]

hmmm, i kind of suspected as much.

do you think a pump would help if it was just before the point where the pipe has to rise?

failing that i suppose the options are: (a) get the inlet to the vertical soil pipe dropped a bit. only problem is there is virtually no space below the boards, just a very hard lime(?) material, so may not be possible. (b) maybe run the shower outlet to the far external wall since that is where the toilet sits and it connects to a different soil pipe, probably on the external wall but not looked. its very thick sandstone though, so again could be a big job.

wish i knew what the neighbours had done, but their shower was in place when they moved in

 

[Richard C]

do you think a pump would help if it was just before the point where the pipe has to rise?

No

failing that i suppose the options are: (a) get the inlet to the vertical soil pipe dropped a bit. only problem is there is virtually no space below the boards, just a very hard lime(?) material, so may not be possible.

There is usually a way around most problems but difficult to advise without seeing the set up you have; is it possible you can install a new waste run externally?

(b) maybe run the shower outlet to the far external wall since that is where the toilet sits and it connects to a different soil pipe, probably on the external wall but not looked. its very thick sandstone though, so again could be a big job.

Your going to be governed by the amount of fall you can get on the soil pipe (around 1 in 40) & maximum length of unvented waste branch; 3m for 40mm diameter waste, 4m for 50mm diameter waste.