Bad smells from the new bathroom sink

[darrenbarber]

First time post, please be gentle!

I've had a new first floor bathroom fitted, so sink, WC and bath with shower over.

The plumbers did a lot of work while I was offsite, so I've got little to no info on how they've plumbed everything.

They had to move the WC from an outside wall to the left hand inside wall, and I know they had a few problems moving the soil pipe to fit the external one. I have no idea if their final solution is correct as i've had floor/wall tiles laid over the floorboards/pipework. There is a pipe visibly joining the external pipe, and the WC flushes correctly as far as I can tell.

Now the new sink is wall hung, on the same wall but 1m further from the external wall. I cannot see what happens to the sink waste pipe after it enters the floor.

But what I do know is that running the sink tap first thing in the morning releases a horrendous smell, definitely human waste, from the plughole.
This smell continues for as long as the tap is on (ie a few minutes, not seconds).

As an amateur I can only imagine why this is. My theories are:

1. The WC pipe to the external pipe is too shallow for the faeces to be fully washed away. This smell is then activated when other water passes into the external pipe somehow?

2. The sink waste pipe is attached to the WC waste pipe somehow before they both exit the building? There is no sign of a seperate sink waste pipe entering the external vertical pipe, so I assume this has to be the case? Is this common practice or a botch-job? Again, is it possible the angle might be too shallow and waste is sitting inside the pipe? Is there any way if they are connected that the WC waste might even backfill into the sink waste pipe?

The distance from the WC to the external pipe is about 0.75m max, and from the sink to the WC is 1m.

Please help, as I don't know whether my plumber/plumbing is at fault or I'm missing a more fundamental drainage problem.
thanks in advance.

 

[mikej2005]

The sink waste pipe is attached to the WC waste pipe somehow before they both exit the building? There is no sign of a seperate sink waste pipe entering the external vertical pipe, so I assume this has to be the case? Is this common practice or a botch-job? Again, is it possible the angle might be too shallow and waste is sitting inside the pipe? Is there any way if they are connected that the WC waste might even backfill into the sink waste pipe?

I have two toilets and two sinks that all join to a horizontal soil pipe before it exits vertically down through the house, so I don't think this is necessarily the cause of your problem.

There are presumably guidelines as to the slope required, although judging by the length of my horizontal run (4-5m) and the distance between the floor and ceiling below (standard), I would think that the drop doesn't have to be much to ensure it flows properly.

Your sink trap should, in theory, help stop smells coming back up through the plug-hole. If you're getting waste water from the toilet entering that trap, then you've definitely got a major problem somewhere, as you should have 2-3ft of height difference between them which should help prevent that. The waste from the toilet will want to take the easiest route - are you sure you don't have a blockage further down perhaps ?

 

[darrenbarber]

Thanks.
There is 2ft height difference on the pipework, so I agree the trap should be doing the trick.
I can't tell if any wc water is in the sink trap, can't see anything obvious.
What is the best way to try and flush the external soil pipe? Off the shelf or dynorod?
If it is wc waste getting into the sink pipe or trap, would that only be due to a blockage or is there some plumbing scenario where the pipework doesn't have the correct valves/vents etc to make the water flow properly causing it to rise into the sink?

 

[big-all]