Plumbing Bath waste with almost no clearance.

[Schmill]

Ok, so everything was going reasonably well with refitting the bathroom until this.
The 'plughole' of the bath is above a section of floor that is directly above the main feed and return circuit to boiler.
From the bottom of the bath to the top of the floor I have about 125mm, and basically that is not enough room for me to fit the banjo / pop-up-plug connection AND one of these traps:

I have seen one of these which may take up less space:

But now comes the questions.
My waste is of single pipe design, that is an internal soil stack that everything flows to.
As I understand it the regs stipulate that the bath must have a minimum 'seal depth' within the trap, and neither of the above traps will give it. Apparently one way to achieve this is to use a shallow trap at the bath, then run the waste pipe to a clearer area, and use an inline trap to give the correct seal depth, and then onto the soil stack from there.

This work around sounds like the most promising solution to me, but I have a couple of questions;

The waste pipe goes from the bath, and travels under the floor, with the basin waste T-ed down into it, and then goes into the soil stack.
Obviously the basin will have it's own trap, so not an issue.
If I have a shallow trap at the plughole, and then a deeper trap further on before the sink 'T' am I going to be at risk of basically having an airlock between the shallow bath trap and the deeper one, and then have problems with the water draining?

If I am having a deeper trap later in the pipework, do I even NEED a shallow trap directly under the plughole of the bath, or would a 90 degree elbow be ok into a length of pipe that then feeds into the deeper trap?

Many thanks

 

[crockett]

There is a minimum depth for trap seal,


http://www.mcalpineplumbing.com/faq.asp


Have a read and see if it applies to your situation, if the original trap was shallow, you can replace like for like. Read into that what you will and apply the regs as it suits

 

[Paul Barker]

Correct the bottom picture hasn't got sufficient (75MM of water) trap so buy a hepVO (waterless) one instead with a 40mm knuckle adapter. The knuckle adapter fits onto your bath drain and the hepVO trap fits to that then the far end of hpVO trap is a compression fixing to 40mm pipe.

 

[Paul Barker]

There is a minimum depth for trap seal,


http://www.mcalpineplumbing.com/faq.asp


Have a read and see if it applies to your situation, if the original trap was shallow, you can replace like for like. Read into that what you will and apply the regs as it suits

starnge it is some years since I did water regs training but it was 75mm then. Also our local building inspector won't pass those shallow traps. He might be behind the times like me or McAlpine might be in the wrong. You decide.

 

[mrgas]

The shallow trap wont comply with regs but will work just fine.

 

[OLLIE20]

Mate if its your own house, and it works, **** the regs, its a bath trap what the worse that can happen, do what makes the job easies for you, trust me no1 will ever pull you up on it when coming to sell the house etc, its a bath trap, who cares?????

 

[Axel]

Make a bath panel out of 1" steel plate and weld it on. Who's to ever see what kind of trap is in there...

 

[rojaca]

Shallow seal was only permittable where the grey water dropped into a hopper head. I suggest you all take a look at Axel's post regarding nursery rhymes and there application of part H. Shame on you all

 

[Schmill]

Ok, this is crazy

I've spent this evening remeasuring everything and trying to make something fit...

The bath side panel is 510mm high, which when fitted to the side of the bath, means that the plughole can only be 100mm above the floor.
The bottom part of the banjo waste (that came with the bath), is about 55 - 60mm, which leaves sod all room for any kind of 'proper' trap. Even fitting just a 90 degree elbow would leave the pipe halfway through the floor, so I don't think a hepVO and knuckle will work there either

If I use a shallow P trap I might just get away with it, and it looks like this;

Bath Waste

• Schmill
• 8 Sep 2010
• 2

So that is with the floor board removed (22mm thick). The beams on the left of the picture are strapped to the side of a joist, in order to support the section of floor that was over the hole.

So I will have to do that, and then run the length of the bath between the bath and floor a piece of waste pipe, at the far end the pipe will then disappear under the floor and run parallel to the joists connecting to the soil stack, with the bathroom sink dropping down into the run about halfway between the soil stack, and where the bathwaste will drop below the floor.

I'm thinking that no only for building regs (75mm water seal), but also because that shallow P (19mm water seal) might dry out quite quick being next to the boiler feed and return pipes (the two 22mm copper pipes in the photo), that I will need some other kind of trap, probably at the far end of the bath before the pipe goes under the floor.

So... what sort of waste do I need at the other end? Presumably some thing that will just be a nice deep U shape going down under the floor and back up again? I will need horizontal entry and exit to it though, and I've not seen that anywhere?
An alternative to that would be if I could fit a hepVO inline with the waste pipe as it ran under the bath, BEFORE it went under the floor, but I'm not familiar with them, so I don't know if ( A ) it would solve the issue of not having a very good wet trap, and ( B ) if they aren't much bigger than the 40mm pipe itself due to space contrainsts?

Thanks

 

[kirkgas]

you could use a bent adaptor (which is used on tank overflow connection) onto the bath grating, swing it to the side, fit a short piece of pipe into a 75mm deep running trap in a position to miss the copper pipes, and sunk into the floor void, swivelled back to line back up with the waste outlet, simples, (my explanation may not be too simple, but google McAlpine and go through the catalogue to get the right bits)

 

[Schmill]

I'm following most of that...

So out through the plughole, then somehow direct the pipe sideways, then into a trap somewhere, then back to the waste?
Not actually sure I have room for a deep trap anywhere at this end of the bath tbh, but also not entire sure what you mean by a "bent adaptor" ?

 

[londonboy]

Couldn't you reroute the copper pipes and fit a standard trap?

 

[Schmill]

Not without some MAJOR works

Would need to lift a large section of the flooring, turn the pipes as soon as they came through the wall, then notch all the joists across the bathroom for the new pipe positions, and then of course rerun those pipes, and also the towel radiator pipes that T off of them.

 

[mb3]

Hi m8, having just been searching for baths etc I came across a bath waste that may solve your problem but it isn't cheap. It's a complete pop-up waste with overflow with the outlet comes out at 90* from the usual wastes, so you could just use a straight pipe from it to a more suitable place for the trap or use one of the in-line traps.

Anyway here it is,
http://www.bathstore.com/_applicati...p-waste-for-single-ended-baths-1611.html?pg=0