How much clearance for bath waste and trap?

[Simplez]

How much clearance do I need for a bath waste and trap? I really can't have the bath waste and trap lower than the floor as I will have issues with getting the pipe to the outside as there is a first floor roof that I cannot cut into.

One possibility is to raise the bath on an inch of wood to get extra clearance - or should that be avoided?

 

[Sonic70]

You can get a shallow trap if that helps.

 

[Nige F]

You can get a Hep V 0 waterless trap and adapters. A shallow trap is only used if the pipe discharges into a hopper - not a soil/vent pipe. The Hep can be used on a soil pipe connection

 

[Madrab]

One possibility is to raise the bath on an inch of wood to get extra clearance - or should that be avoided?

Ideally you would look to adjust the waste if you can. Unfortunately a shallow bath trap seal can easily be pulled if it discharges into a stack. If it absolutely can't be run without lifting the bath then no reason not to do that, just use a wide enough baton on the floor to give the legs/feet enough support on the floor. Just remember the height of the bath panel too.

 

[Simplez]

You can get a Hep V 0 waterless trap and adapters. A shallow trap is only used if the pipe discharges into a hopper - not a soil/vent pipe. The Hep can be used on a soil pipe connection

There is about 10-11cm clearance under the bath to the floor. So as long as the bath trap can fit in that space then I can get it out through the wall. The pipe will discharge into a hopper.

 

[Simplez]

Ideally you would look to adjust the waste if you can. Unfortunately a shallow bath trap seal can easily be pulled if it discharges into a stack. If it absolutely can't be run without lifting the bath then no reason not to do that, just use a wide enough baton on the floor to give the legs/feet enough support on the floor. Just remember the height of the bath panel too.

What does pulled mean in this context?

The waste will discharge into a hopper.

I could to add a few cm secure the bath feet onto battons - then use an mdf side panel which is height adjustable with its plinth.

The bath will be a reinforced straight bath as it will also be used for showering.

 

[denso13]

Even with a normal 75mm deep seal trap the outlet will be above the floor. Yes, the bottom of the trap will be below the floorboards but the outlet height is much the same on all traps.

 

[JimCrow]

I take it you want the trap outlet as high as possible off the floor, this trap might be your best bet, the centre of the outlet on this trap is around 30mm higher than the bottom of threads on the bath grating,
https://www.plumbparts.co.uk/product/mcalpine-60mm-seal-anti-syphon-extended-body-bath-trap-sm10ev/

 

[Madrab]

What does pulled mean in this context?

When a trap is 'pulled' it means that there has been a vacuum on the downstream side of the trap that has sucked the water seal out of the trap. When there are numerous outlets feeding into a soil stack, there can be the occasion where there is a vacuum created on the back of the trap connected to a shared waste system (basin/sink/shower etc). With a shallow trap there is only 19odd mm depth of water and it doesn't take a lot to pull that water out of the trap, either by the shared waste or by the draining bath water itself (self syphoning) and then it can let sewer smells in. That's why proper ventilation of a waste system is very important

When an open ended waste pipe runs into a hopper then there is a reduced chance of a vacuum being created and the trap being 'pulled' but it can still pull itself.

A bath, if set to a normal height, when the trap is fitted it's outlet should still sit above the floor level as @denso13 suggests. You may have to cut a little of the floor out to accommodate the bottom leg of the trap, bath height dependent.

 

[Simplez]

So when I have the bath fitted my options will be - one of the following. I take it all are acceptable or is one type of trap better than another? Or should I avoid the combined bottle trap and waste overflow?

1

2

3

 

[Madrab]

Option 2 - with or without the anti vac are the preferred option.

Option 3 if you have the space, option 1 as the last resort.