Connecting the bath waste to the soil stack

[aa44]

I am trying to plan the plumbing for my new house.

One of the bathrooms will be on the ground floor which will have a solid concrete floor. I need to connect the bath waste to the soil pipe but obviously don't have a huge depth to do it in. The distance between the bath waste and the soil pipe won't be massive. If I use a HepVo trap on the bath and then connect to a boss on the soil pipe at the lowest possible level above the floor (i.e. with the base of the boss sitting on the concrete) am I likely to have any problems?

The bath might be something like a Kaldewei Saniform which appears to have a gap of about 125-145mm between the bottom of the bath outlet and the floor. I can get about another 30mm by not laying any flooring round the soil pipe so that would give me about 155 - 175mm between the bottom of the boss and the bottom of the bath outlet. Into that space I need to get the HepVo and presumably a banjo for the overflow and maybe 5mm vertical drop for the slope.

Any problems with my plan? (I know that I need to have at least 450mm from where the waste pipe joins the stack to the bottom of the rest bend).

Is there any advantage in using a shallow P trap before the HepVo to connect the overflow rather than using a banjo?

While I'm on, I need to join the shower waste at probably the same level. Am I right in thinking that I can join two waste pipes to the soil pipe at the same level at a 90 degree angle but not directly opposite each other (i.e. 180 degrees)?

Hope this makes sense.

 

[muggles]

OK first things first, you may not use a shallow P trap on a bath, or indeed on anything going into a soil stack. The minimum trap seal depth for a bath running to a stack is 50mm, shallow P traps typically give 19mm. You can, however, use a proper bath trap like this one:

This will have the added advantage of giving your waste pipe a higher 'starting point' than a HepVo trap would, thereby increasing the available fall. The fall on the waste pipe should ideally be 44mm per metre (2.5º), however falls as low as 18mm per metre are acceptable but not recommended. 18mm per metre is the absolute minimum.

I see no problem with connecting the two wastes on opposite sides if this makes things easier, however what you absolutely must not do is connect either directly opposite a W/C connection, or anywhere in the opposite half of the pipe within eight inches below that connection. This is a prohibited zone for the prevention of crossflow (IE poo going into your shower/bath waste).

 

[aa44]

Thanks for your help.

AA

 

[Schmill]

Have a similar situation myself, except mine is an upstairs bathroom, but the pipes feeding the boiler run just under the floor bewlow where the waste hole for the bath is
To make sure I understand this trap correctly...

Am I right in thinking the left vertical port connects to the bath waste / plughole, the right vertical port (with the elbow) connects to the outgoing waste pipe, and the bottom horizontal port just has a sealing cap fitted to it, for the pprovision of unblocking it if it clogs?

Thanks

 

[Hugh Jaleak]

Yes.