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Sewage smell in house AFTER drains have been unblocked

(15 Posts)
Coleoptera Sun 01-Dec-19 16:45:37

I had to have our drains unblocked by Dynorod 3 days ago. They found a massive and complete block and did the usual water-blasting through the main 2 drains in the driveway. The blockage was cleared (saw this on camera) and all household plumbing was working again. There'd been no smells - just a blocked shower and a couple of slow draining sinks that prompted my call out.

However, we now have a disgusting smell of sewage located I think near an old groundfloor sink and washing machine - or - probably more likely - in a room that was converted from a garage, which was built (by previous owners) over another main drain!

This drain was inaccessible at the time of the unblocking by Dynorod, as it's underneath a carpet and a lot of heavy gym equipment and piano (our mini gym and music room). But the smell is probably worst in this room. No smell was detectable before the drains were unblocked. So I don't know why the smell is there now.

I've done all the usual things like ensuring there's lots of water flowing through that drainage area - from the groundfloor shower (the one that originally blocked), the old sink and the washing machine. But although the smell is masked when the washing machine is on, it's absolutely terrible if we come back to the house having been out and isn't getting any better.

Could it be that the high-pressured blasting of water has cracked the indoor drain under the room? However, surely the drain cover would block the smell - plus the carpet? Is there an undetectable P trap that's dried out? But if so, then why does the smell not go away now I've kept running water through the system?

PigletJohn and anyone else with any idea - can you advise me please?

Will I need to call out Dynorod again? They weren't initially very good and told me there was no blockage at all until I insisted on further investigation and then they found a massive and total drains block. I'm worried they'll say we need to take apart the groundfloor room to look at that drain, only to find that this isn't the issue at all. This would involve lots of expense and disruption and I'm hoping it's something less invasive.

Any ideas anyone?

Coleoptera Sun 01-Dec-19 17:59:24

Oh, just to add, in case it's relevant, when the washing machine is on, there's a sounds like water gurgling up in the sink next to it. Might that indicate some dried out air trap? However, this has always happened long before the sewage smell began.

The smell might be most strongly situated behind the washing machine where there are pipes - one of them being a very old one which I suspect is made of lead. The pipework then goes under the flooring and I assume towards the drain in the adjacent room (which has the drain shaft underneath the flooring).

Would high pressure blasting of the blockage have somehow adversely affected the pipework/ P trap that's somewhere underneath the floor, rather than at the specific area where the drain shaft is? I don't know what the underfloor pipework consists of, just beneath a washing machine. Would there be part of the drainage system under the floor that should have an airtrap, which might then have been affected by the water blasting?

Coleoptera Sun 01-Dec-19 22:01:26

PigletJohn - legendary MN expert - are you around? Anyone?
I've been researching on the internet as much as I can to find a solution - but am still unsure of the source of the smell. Pretty clear now though that it's mostly from behind the washing machine pipework. It only started when we had the drains unblocked but although the smell is temporarily masked when I put on an empty 90C wash, it doesn't clear and the whole groundfloor and parts of the upstairs now smell disgusting.

It's definitely not coming from the shower tray (which I know can be problematic due to low profile shower tray easy-plumb wastes) - as I've had a good sniff there and it's fine.

Should I call out Dynorod again or try a local plumber? The latter may not have all the equipment that a drains company do. Any ideas anyone at all?

Coleoptera Mon 02-Dec-19 11:52:52

Still looking for advice from anyone on MN. Dynorod have fobbed me off and said that after a blockage has been cleared, it can take weeks for the sewage smell to clear. Has anyone heard of that before?

However, when the drains were blocked, there was no smell at all. I've had the washing machine on countless times, we've had lots of showers, run water through the sinks, cleaning fluids etc etc and the smell is pervading the whole ground floor of the house.

Bumping my thread in case anyone can reply?

johnd2 Mon 02-Dec-19 12:58:21

No idea why noone else has replied but the gurgling is basically either a blockage in that part of the drain or the pipe has standing water ie going uphill.
I wonder if there is a further blockage in that area which needs dealing with.
The smell would be caused by the water in the trap being sucked through by the narrow gap beside the blockage. Either that or one of the traps is losing its water or dislodged.
Have you tried running just a trickle of water slowly down all the drains, to make sure there's not enough force to cause gurgling?
The final option would be either start pulling up floors or get a camera in from all directions.

johnd2 Mon 02-Dec-19 13:03:08

There shouldn't be any traps under the floor, and when you put a trickle of water in that would be a cup full in each.
The actual smell from an open drain is not caused by your pipework but basically anyone on the same run, the sewage is basically nicely steaming away in the pipe and obviously very smelly. The drains are all ventilated on people's roofs, so if the wind is blowing your way, the smell comes through.
We had an open pipe on our system while they were building our extension, and it was fine most of the time but occasionally we got the full benefit of the neighbours...

Coleoptera Mon 02-Dec-19 13:15:31

Many thanks Johnd2 for replying. That's really helpful.

When you say the gurgling is possibly a blockage in that part of the drain, do you mean in the narrow waste water pipe leading away from the washing machine and/or the sink?

The washing machine was plumbed in right next to and below the sink and I think both drain into the same waste pipe. The gurgling has always happened since we got the washing machine plumbed in and long before any blockage or any smells.

The smell seems to be strongest at the back of the washing machine where there are various in-pipes for water and out pipes for waste water. But it's also pretty strong in the room under which there's an old drain shaft that's completely covered up by flooring and carpet.

Dyno have now said that sewage smell is 'normal' after a blockage has been cleared but I'm not convinced this is definitely the cause. Have you heard of this being the usual result of having a blockage cleared?
Surely if the drains are now running clear and the traps are all working, plus vents, then if anything, there should be less smell than before - and there wasn't a smell at all in the first place - just a block?

Where exactly would the traps be in the vicinity of the sink and washing machine? I assume there's one under the sink and presumably there should also be one under the washing machine area? Is that correct?

I'm not sure what you mean about running all the water slowly down all the drains? All appliances and sinks have been in regular use across the last few days but the sink only gurgles when the washing machine is draining.

Any further thoughts and ideas? I feel as if I'm becoming a plumbing and drains expert!

PigletJohn Mon 02-Dec-19 15:57:50

I think you'd do well to get an experienced local plumber to take a look.

The skillset of dynorod workers may vary.

I incline to the view that drains should not get blocked unless you put toys, sanpro or cement down them, so there is probably a construction or damage fault. It may have been caused when the extension was put on top.

Haver a look behind your machine and photograph the waste pipework. There is often a standpipe for a dishwasher or washing machine, it should have its own trap.

Your soil pipes should have a vent. Usually it is a 100mm pipe that rises up the outside wall of the house (sometimes in a duct inside the kitchen and bathroom, boxed in) that is open at the top to let air in and out, equalising the pressure, and to allow and odours or gases to escape above the hight of your windows.

Bathroom fitters sometimes like to put a Durgo or similar valve in, which is supposed to let fresh air enter the pipe when there is suction, and supposed to prevent smells coming out. They don't always work well, and they may stick.

Coleoptera Mon 02-Dec-19 16:59:06

PIgletJohn, many thanks for replying. That's very helpful of you.

Dynorod have been back out but reached no definite conclusion and have said to wait a week and then see if the smell clears.

Meanwhile, they put 'smoke-bombs' into the drain nearest the house and then came inside to see if the chemical smell released when there's sewage gas, would be detectable. He and I couldn't detect anything much at all - so concluded that there's no obvious place where sewage gas is escaping into the house - BUT - there's still a strong smell of sewage. This is strongest behind the washing machine and within the room that was built over a drain entrance.

He said that he'd discussed the case with a senior colleague who said the only thing is to rip up the carpet and flooring in that room and then get a camera down that drain between there and the washing machine, the shower and the downstairs toilet that all feed into that drain, so see if there are any cracks/any damage. As this would be a big disruptive job, involving taking apart a room, moving everything in it and ruining the carpet, he said wait a while and see if the smell really does persist.

Meanwhile, he found that the drain had re-blocked - but at the top of the driveway at the last drain shaft before it then goes into the public sewage system. He didn't know why that would have happened as he'd unblocked it all the other day. We speculated whether the drain ran uphill bit it doesn't seem to as the shaft is deeper than the one nearer the house. He suggested that because it had blocked there again then that might explain the smell in the house but now he's cleared it again and the smell is still there.

Regarding the wastepipe behind the sink and washing machine, he took a look at this and the washing machine has been plumped straight into the sink waste pipe under the sink so it shares a trap there but he didn't think it had dried out and said that if there were a problem there, then we'd have the sink blocking and it's not blocking at all. If they share a trap, will that be a problem? The smell doesn't seem to be coming up from the sink but more, behind the washing machine where there's a very old waste pipe running into the floor.

The soil vent pipe outside, near this whole area, isn't emitting any smell as far as I can tell, although it's above the roof line. There's no smell outside - only inside the house. It doesn't have a Durgo valve fitted as far as I know and has never been a problem.

The man from Dynorod suggested that having cleared the drains blockage the other day, then this might then have acted like a 'cork' plugging the pipes from smells and now it's released, the smell is there. But this doesn't make sense to me as surely the 'plug' itself would have been very smelly and we didn't have a problem with smell until after the blockage was cleared? In any case, the new and unexplained blockage further from the house would surely be 'plugging' the smells again - if indeed that made any sense in the first place?

Any further thoughts? I really appreciate your help.

PigletJohn Mon 02-Dec-19 18:02:51

photos might help

opening up the hidden cover will probably help. There could be a disused pipe under there or some other damage.

PigletJohn Mon 02-Dec-19 18:04:02

where is the soil vent pipe, and how high? If it is free and open, gases should be escaping up there, not into the house. Has he sniffed it?

PigletJohn Mon 02-Dec-19 18:05:49

I want to see the route the flexible waste pipe from the machine takes, on its way to the sink waste.

SofiaAmes Tue 03-Dec-19 02:53:35

I am such a plumbing nerd...I LOVE these threads. @PigletJohn if you ever want to take a family vacation in Los Angeles, I have a large house and plenty of extra bedrooms and would be happy to host you and your family if you promise to talk plumbing with me....smile

Coleoptera Tue 03-Dec-19 15:33:04

PigletJohn, I'm afraid I can't do photos but I'll try to describe the route of the flexible waste pie from the washing machine to the sink: the flexible waste pipe comes out of the back of the washing machine, loops round the back of a cupboard under the sink and the feeds into the front of the P trap which has the sink feed coming about this. There isn't a localised sewage smell in this area - just a generic one.

The soil vent pipe is high above the roof line, above the area of the downstairs toilet and upstairs toilet . I can't reach up there - and nor could the Dynorod man- but there's no discernible smell coming from near there or outside. The smell is in the house.

In the last 24 hours I've also now developed the classic symptoms of sewage gas exposure - nausea/diarrhea/headache/sore throat - and have been up all night ill. It might be a coincidence and just a virus of course. DCs are showing no symptoms themselves. Maybe it's exposure to raw sewage each time I've been helping/observing/talking to the Dynorod man.

If we have to take up the carpet and flooring in the indoor room with the drain shaft, I'm worried that the coiled hose for the camera - which is on a heavy reel - will be dragged through the house covered with microscopic ecoli/sewage dragging on the carpets etc, as it's pretty dirty and was only for use outside. I'm also worried that the high pressure water clearing - if they need to do that indoors - will also spray sewage on walls and flooring and furnishings.

Dynorod have told me to wait for at least a week and see if the smell clears. Would you advise me to look for a local plumber to give a second opinion in the meantime? The trouble is that plumbers aren't necessarily going to have equipment to explore drains nor the technical knowledge about drains, as opposed to plumbing.

PigletJohn Tue 03-Dec-19 18:25:27

when the waste pipe connects to the trap, does it then run downwards (so that waste from the sink can run down it) or does it loop up and touch the underside of the worktop, retained by piece of string, cuphook or something?

First rule of plumbing: flows downhill.

An experienced wrinkly plumber will have seen most of the things that can go wrong with domestic drains so may spot something. I'd suggest (if you can find one by personal recommendation) offering to pay for an hour of their time to rummage around.

I would not be surprised if there is a defect, dip, deadleg or something where dislodged detritus is collecting. But as you have an open soil vent, it's puzzling to know where else the smell is getting out.

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