Can I connect bath and sink waste pipes?

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Hi All

I'm just in the process of fitting a new bath and sink and would like to tidy up the waste pipework. At the moment the bath has a 40mm pipe going through the outside wall into a hopper and the sink has a 32mm pipe also going through the outside wall into the hopper. I'd like to join the two together but as a DIYer I'm not sure if this is against building regs or if joining the two will cause problems. I suspect that draining the bath could cause negative pressure may empty the sink trap so I may need to fit some sort of valve?

Another problem is the actual hopper itself. The hopper and waste pipe are mounted on the back wall of the house however there is a conservatory on the back of the house and the hopper is actually below the level of the conservatory roof, hence in the house... sort of. Why it hasn't been moved is a mystery......

Problem is it gets a bit smelly so I'd like to seal it off as the same time as tidying up the pipes. Is there any reason why I cant seal off this pipe? Nothing else uses the pipe or the hopper..
 
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Separate wastes are always preferred; if you must interconnect fit a Hepvo waste to the sink or you will draw the trap;
http://www.plumbworld.co.uk/hepv0-self-sealing-waste-442-1788

You can’t just remove the hopper & have direct connection as air must be allowed to get into the system; remove the hopper, replace it with a vented soil stack & tee your bathroom wastes into that.
 
All makes sense but the hopper pipework is a smaller diameter to a normal soil pipe, presumably this is the original rainwater pipe pre the conservatory? This would make sense as its on the opposite side of the house to the soil pipework. Another worry is why the smell, is this nomal or has someone bodged the pipework in a neighbouring property (there are some real bodged extensions on the street).

I also cant seem to locate a vent smaller than a normal soil pipe, are they actually available?
 
Strange things going on; wrong thread, already deleted this once :confused: be back later
 
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All makes sense but the hopper pipework is a smaller diameter to a normal soil pipe, presumably this is the original rainwater pipe pre the conservatory? This would make sense as its on the opposite side of the house to the soil pipework.
Are you saying the bathroom waste is being dumped into the surface (rain) water drain? That should not be happening unless they all discharge into the foul drain system. No longer allowed but common in the past.

Another worry is why the smell, is this nomal or has someone bodged the pipework in a neighbouring property (there are some real bodged extensions on the street).
As I’ve already said, if it’s an open hopper system, it’s very likely to smell & why they aren’t used anymore; or are you saying there is a general smell wafting about the place?

I also cant seem to locate a vent smaller than a normal soil pipe, are they actually available?
Regs allow vent pipes (dry portion only) to be reduced to 75mm but the nearest your going to get to that is 82mm & even that may be difficult to get unless you go to a large Builders Merchant or distributor; DIY sheds don’t stock it. You’re then going to have to get an adaptor to reduce it down to what you’ve got; personally I’d cut it off at ground level & put in an new 110mm plastic vented stack.
 
Carried out a bit more research.

House is a a 1930s semi, all the pipework looks to the same as the rest of the houses on the street.

Lifted the manhole cover in the back garden and found a gentle flow of water, no smell at all and the gullys look remarkably clean. Ran a hose into the hopper at full pelt and watched the water increase in flow down the gully. The waste from the kitchen flows into the usual type of gully below the window so ran the hose into this and again the water increased in flow down the back garden gully but noticeably less this time. Presume this is a two pipe drainage system. Pipe is about 69mm dia.

The smell comes and goes, sometimes nothing for a week or more but now I'm not so sure its just coming out of the hopper, It may also be wafting in out of the gully underneath the kitchen window. Get the feeling that the pipework between the kitchen and the gully in the back garden might be the real culprit. At the moment there is almost no smell from the hopper.

Hopper pipe is concreted in so no hope of installing a 110m vented stack at ground level.. :cry:
 
Carried out a bit more research.

House is a a 1930s semi, all the pipework looks to the same as the rest of the houses on the street.


It may also be wafting in out of the gully underneath the kitchen window.
:
That`s the most likely source :idea: source some Jeyes fluid and dose it with that :idea:
 
If this kind of system is not allowed any more, what are you meant to do about it?

I am also in a 1930s house and have the same system - bath waste water goes into hopper and then into an open drain. No smells (yet) but it's not a very good system.
 
Was common practice in that era to discharge basin/bath wastes into a hopper. Always was an unsanitary affair, smells often became a problem, for that reason the idea was abandoned, and it is now against regs to fit a hopper other than as a direct replacement.

Best plan is to do as suggested by Richard, fit a 110mm stack. Often the hopper was fitted adjacent to the 4" cast iron soil pipe that served the bathroom W.C., replace this with 110mm plastic, and join wastes into that. Remove (now redundant) hopper.
 

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