How should Waste Plumbing be Setup?

Have recently completed build of our house. Over the weekend I discovered a smell of waste in our main bathroom coming from the shower waste plug.

It turns out the shower water run's out to a gully, and the gully is connected to the main 4" waste pipe for toilet waste running around the house out to the mains sewage. The waste from the main 4" take away has flowed down into the gully, the smell of which is making it way up through the shower waste pipe.

My question is, should the gully fitting for shower waste be connected to the 'toilet' waste piping running around the house? It doesn't seem to make any sense to me but I'm not a plumber?

Any advice would be appreciated.

The shower waste should have (and probably does) a trap that creates a water lock. This is the same as a sink trap in function, and is there so that smells etc. cant come back.

As you have just finished the build, has the shower been used? If not, then it is possible that the trap has no water in it, and that is why the fumes are coming up.

Solution: pour a jug of water into the shower to seal the trap.

The rest of the plumbing sounds normal enough to me.

Hi buddyboy

Thanks for the info. No the shower hasn't been used yet so there wouldn't be any water in the trap yet, i spoke to the groundswork guy and he said pretty much the same thing.

But should the waste from the straight 4" waste flow into the gully that the shower runs out into? Not really happy with this and doesn't seem very hygenic that waste is just sitting in the gully not even fully covered by a solid lid?

if your groundworker is still on site is it safe to assume the works are not complete? There should be a plastic cover for the gully/AJ and im sure the will be ftted upon completion.
Shower and toilet are classsed as foul and run in the same line to the treatment system

No groundworks guy is well finished, I rang him to get him to come back to sort it. The gully only has a partial 'grilled' lid, so you can see into it.

The problem seems to be that the bend and connecting piece coming out of the gully should be dropping down into the main 4" run which would be at a lower level than the gully, instead the connection drops from the 4" striaght run down into the gully allowing waste to divert and flow into the gully.

dj01 said:

The problem seems to be that the bend and connecting piece coming out of the gully should be dropping down into the main 4" run which would be at a lower level than the gully, instead the connection drops from the 4" striaght run down into the gully allowing waste to divert and flow into the gully.

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Hmmm, how it should be........

The waste from the toilet goes into a 4" waste pipe which goes outside into a 4" (normally underground) waste pipe that goes to to the main sewer or septic tank. At any bends there will normally be an AJ, which is a capped box used for inspection and unblocking. This whole run should be enclosed.

connected to the 4" waste pipe will be gullys, which are open grilled u-bends. The U bend will be full of water, creating a seal that stops fumes etc. from the 4" pipe from getting out (The same as the shower or sink u bends in function). Water from showers and sinks (and washing machines and dishwashers) will flow into these gullys, and will drop down from open pipes ( 1 3/4" if I remember correctly). The gully is normally covered with a plastic grill, to stop leaves etc. getting into the water in the u-bend. The gullys should be stuated above the 4" waste pipe so that waste can't flow into them.

That is the way it is supposed to be set up.

From what you describe, it sounds like the exit of the gully is at the same level as the 4" waste pipe, so anyone flushing a toliet "upstream" will get into the water in the gully u-bend.

Can you re-check and confirm I understand you correctly. And that the gully also has water in it to create the seal mentioned.

To be honest, I think it is easier to get it right than wrong (Although Ive seen some amazing examples to the contrary). This isn't rocket science, and hasn't changed for a long time.

Thanks buddyboy. The bottom of the gully is actually at a lower level than the main 4" waste running around the house.

The connecting piece's between gully and 4" comes out of the bottom on the gully, points upwards (its not a u-bend though), straightens and joins into the 4" main run.

So the problem is some of the waste passing in the 4" is able to divert, and drop down into the gully. What should happen is the connection into the main 4" should go be pointed slightly upwards, and then connect into a u-bend as you describe, this way waste can't divert into the gully as it passes.

dj01 said:

Thanks buddyboy. The bottom of the gully is actually at a lower level than the main 4" waste running around the house.

The connecting piece's between gully and 4" comes out of the bottom on the gully, points upwards (its not a u-bend though), straightens and joins into the 4" main run.

So the problem is some of the waste passing in the 4" is able to divert, and drop down into the gully. What should happen is the connection into the main 4" should go be pointed slightly upwards, and then connect into a u-bend as you describe, this way waste can't divert into the gully as it passes.

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Sounds like we're both saying the same thing. Which unfortunatly sounds like the wrong thing

I'd suggest the course of action now is to get someone to look at it, either an engineer or other professional, and get them to state that it is incorrectly set up.

Then you have to start chasing the builder or whoever is responsible.

Yes unfortuately I think it wasn't done correctly, so I'm waiting on the guy who did the work to come back and look at it.

Thanks again for all the help!
dj01