Foul sitting in pipes
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kdj
- Posts: 3
- Joined: Sat Feb 25, 2006 6:47 pm
- Location: essex
Hi, We have just had a cctv camera put down the drains of our 3 year old house, as requested by NHBC, to try to ascertain why we have such a terrible smell of sewage wafting from our downstairs cloakroom sink. The camera found that waste is sitting in the pipe and that it is not flushed away with a single flush of the downstairs toilet - the downstairs toilet is on separate drain system to the other toilets in the house. The crew had to flush the toilet several times to get any water to come through into the drain at all, but we were told that as it did eventually unblock, that this does not constitute a blockage. This is the second time we have had a camera investigate the drain - the first time they lost the footage - and exactly the same thing was found then as well. We are now not using our downstairs toilet in an effort to keep our air clean! The builder had previously said that they would probably put a pipe out of the front of our house to vent the gases from the toilet, but this seems to us to be merely disguising a problem - the smell will still be produced, but it will be outside the front door instead surely? Can anyone advise us as to why the waste doesn't flush away properly and what the best course of action might be? Thanks
--kdj--
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TheRobster
- Posts: 83
- Joined: Fri Sep 24, 2004 10:04 pm
- Location: Leeds, UK
The most likely explanation is that the pipe gradient isn't steep enough. This means that the velocity of the water from the toilet is too low to carry the waste away and it simply settles in the pipe.
When the crew flushed the toilet several times to unblock the pipe, did they completely remove all the blockage? If not then another possibility is that you've got a permanent lump of "something" in there and this is retarding the flow, causing waste to build up at that point. Could be hard-packed sediment, a big lump of grease or something similar. Could be that someone tried to flush something down the toilet in the past and it got lodged in the pipe.
If the pipe was completely cleaned and it still blocks, then the most likely bet is that it's the first problem I outlined (flow velocity is too low). Off the top of my head, the most obvious solutions are:
1) Re-lay the pipe at a steeper gradient (if this is feasible)
2) Replace the pipe with one made from a material with a lower coefficient of friction (i.e. a pipe that is 'smoother' than the existing one). Whether or not this would work depends on the material of the existing pipe. If the pipe is old it's probably made of iron, concrete or clay. If you replace it with a modern PVC pipe then this should lower the friction between the wall of the pipe and the water/waste mixture and blockages should be less likely to occur.
3) Increase the flush volume of the toilet (less certain to work but probably easier to do). Most toilets nowadays are of the low-flush variety though...usually between 6 and 7 litres per flush. I aren't even sure if you're 'legally' allowed to fit anything with a flush volume greater than this (if you're in the UK at any rate).
I'm also assuming that the pipe isn't damaged in some way? I would have thought that the CCTV would have picked up any cracks in the pipe or ground shifts.
When the crew flushed the toilet several times to unblock the pipe, did they completely remove all the blockage? If not then another possibility is that you've got a permanent lump of "something" in there and this is retarding the flow, causing waste to build up at that point. Could be hard-packed sediment, a big lump of grease or something similar. Could be that someone tried to flush something down the toilet in the past and it got lodged in the pipe.
If the pipe was completely cleaned and it still blocks, then the most likely bet is that it's the first problem I outlined (flow velocity is too low). Off the top of my head, the most obvious solutions are:
1) Re-lay the pipe at a steeper gradient (if this is feasible)
2) Replace the pipe with one made from a material with a lower coefficient of friction (i.e. a pipe that is 'smoother' than the existing one). Whether or not this would work depends on the material of the existing pipe. If the pipe is old it's probably made of iron, concrete or clay. If you replace it with a modern PVC pipe then this should lower the friction between the wall of the pipe and the water/waste mixture and blockages should be less likely to occur.
3) Increase the flush volume of the toilet (less certain to work but probably easier to do). Most toilets nowadays are of the low-flush variety though...usually between 6 and 7 litres per flush. I aren't even sure if you're 'legally' allowed to fit anything with a flush volume greater than this (if you're in the UK at any rate).
I'm also assuming that the pipe isn't damaged in some way? I would have thought that the CCTV would have picked up any cracks in the pipe or ground shifts.
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TheRobster
- Posts: 83
- Joined: Fri Sep 24, 2004 10:04 pm
- Location: Leeds, UK
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flowjoe
- Posts: 1136
- Joined: Sun May 08, 2005 9:25 am
- Location: North West
It shouldnt really matter if foul waste is holding in the system if it doesnt lead to a blockage, a three year old house will have plastic/clay pipe work which is as smooth as you can get internally and the waste should push through.
The worry is that you are getting internal venting toilets, sinks, baths etc are fitted with traps to prevent venting from your system and ultimately the main sewer they discharge into.
It sounds as though water is being drawn out of an internal trap due to a vacuum when the toilet is flushed, leaving a direct vent into the property, i suspect that your buiders are talking about fitting an air admittance valve to the front of the property which will allow air into the system, but doesn`t allow the system to vent out.
The valves are not designed to work outside as frost or ice will stop them working, they can be fitted to the rear of the WC and you can also buy sink/bath traps with valves fitted,
When you flush the toilet keep an eye on the water level in the sink/bath/shower trap, you may well find that the level moves up and down, if so just run the tap each time the toilet is flushed to fill the trap again and seal the vent.
Edited By flowjoe on 1140947905
The worry is that you are getting internal venting toilets, sinks, baths etc are fitted with traps to prevent venting from your system and ultimately the main sewer they discharge into.
It sounds as though water is being drawn out of an internal trap due to a vacuum when the toilet is flushed, leaving a direct vent into the property, i suspect that your buiders are talking about fitting an air admittance valve to the front of the property which will allow air into the system, but doesn`t allow the system to vent out.
The valves are not designed to work outside as frost or ice will stop them working, they can be fitted to the rear of the WC and you can also buy sink/bath traps with valves fitted,
When you flush the toilet keep an eye on the water level in the sink/bath/shower trap, you may well find that the level moves up and down, if so just run the tap each time the toilet is flushed to fill the trap again and seal the vent.
Edited By flowjoe on 1140947905
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kdj
- Posts: 3
- Joined: Sat Feb 25, 2006 6:47 pm
- Location: essex
Hi All,
Thanks for all the replies - basically, NHBC is investigating, but they don't want to get involved unless they absolutely have to. I am of the opinion that they will try to wriggle out of doing anything, which is why I posted, so that I might be able to come back with something sounding vaguely knowledgeable when they give me their report! NHBC only became interested when I contacted the ODPM as the contractor I had called from Drain Doctor thought that none of the houses in our drain run had an open vent which contravenes building regs, Part H. NHBC, when they came out to inspect that said that the downstairs toilet was on a different drain system to the toilets on the other 2 floors of the house - there is a manhole at the front of the property, but the toilet actually drains through to the back - meaning all the pipes are under the house, which the CCTV guys said is not really a great way to do it. There is another manhole at the back, which the other toilets and sinks drain into. Goodness knows what the one at the front is for, as no-one seems to know... Next to the toilet, all the pipe work is boxed in and in the corner there is a covered sort of stack (best way I can describe it with my v limited knowledge!) The builder (and by this I mean the house builder) has said that they would build this stack up by another 6 inches or so, and then stick a pipe outside from this.
Re the question about the water level in the toilet - this does go down at times and Drain Doctor said that this showed that the traps were being sucked out. In his report he put that it appeared that of the 16 houses in the drain run, all had air admittance valves - I have since been told that you can't tell if there is an open vent in a house without going into the roof space to see. As NHBC have insisted that the downstairs toilet is not on the same drain system and does not use the system that the durgo in the roof is venting, they say they do not need to inspect the other properties to see if the property at the head of the drain run has the open vent or not.
As for how long the smell has been going on - about 10 months! After we moved in - one day there was no smell, next day there was a terrible smell and we have had it ever since. We have only ever put the usual stuff down the toilet!!
The CCTV guys said that they thought NHBC would come back and say that there was nothing wrong with the drain, so they could help no further, but he said he would put in his report that the smell was really very bad and that a plumber should come to look at the venting and traps. Hopefully NHBC will be in touch this week...
Thanks for all the replies - basically, NHBC is investigating, but they don't want to get involved unless they absolutely have to. I am of the opinion that they will try to wriggle out of doing anything, which is why I posted, so that I might be able to come back with something sounding vaguely knowledgeable when they give me their report! NHBC only became interested when I contacted the ODPM as the contractor I had called from Drain Doctor thought that none of the houses in our drain run had an open vent which contravenes building regs, Part H. NHBC, when they came out to inspect that said that the downstairs toilet was on a different drain system to the toilets on the other 2 floors of the house - there is a manhole at the front of the property, but the toilet actually drains through to the back - meaning all the pipes are under the house, which the CCTV guys said is not really a great way to do it. There is another manhole at the back, which the other toilets and sinks drain into. Goodness knows what the one at the front is for, as no-one seems to know... Next to the toilet, all the pipe work is boxed in and in the corner there is a covered sort of stack (best way I can describe it with my v limited knowledge!) The builder (and by this I mean the house builder) has said that they would build this stack up by another 6 inches or so, and then stick a pipe outside from this.
Re the question about the water level in the toilet - this does go down at times and Drain Doctor said that this showed that the traps were being sucked out. In his report he put that it appeared that of the 16 houses in the drain run, all had air admittance valves - I have since been told that you can't tell if there is an open vent in a house without going into the roof space to see. As NHBC have insisted that the downstairs toilet is not on the same drain system and does not use the system that the durgo in the roof is venting, they say they do not need to inspect the other properties to see if the property at the head of the drain run has the open vent or not.
As for how long the smell has been going on - about 10 months! After we moved in - one day there was no smell, next day there was a terrible smell and we have had it ever since. We have only ever put the usual stuff down the toilet!!
The CCTV guys said that they thought NHBC would come back and say that there was nothing wrong with the drain, so they could help no further, but he said he would put in his report that the smell was really very bad and that a plumber should come to look at the venting and traps. Hopefully NHBC will be in touch this week...
--kdj--
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flowjoe
- Posts: 1136
- Joined: Sun May 08, 2005 9:25 am
- Location: North West
Its a three year old property with a 10 year guarantee and NHBC aren`t interested, nothing new there then.
Most modern properties have internal soil vent pipes within the roof space, pain in the a*?se but thats progress for you.
Forget looking at the other properties i suspect this problem is local to yours, modern drainage systems have rubber sealed joints, a leaking drain below ground does not vent through the sub-soil, through a concrete floor slab and into your bathroom/ D/Stairs WC. If you don`t have a sub-floor space then its a waste of time looking at the drainage system when it is obviously a venting problem
At a guess the sink/hand basin connects into a boxed in stub/stack shared with the toilet, on a line upstream of the main soil vent pipe, as a result when you flush the toilet there is a vacuum, which empties a sink trap.
There may be a boxed in air admittance valve which has failed, but raising it up 150mm will not help, NHBC will not help you out because this is due to poor construction.
Give the NHBC contractor a week. if you don`t get a satisfactory answer, notify NHBC/your builder that you will get a decent contractor in and pass the invoice on to them.
I suspect you may well be better off with a local plumber rather than a franchised drainage contractor.
Most modern properties have internal soil vent pipes within the roof space, pain in the a*?se but thats progress for you.
Forget looking at the other properties i suspect this problem is local to yours, modern drainage systems have rubber sealed joints, a leaking drain below ground does not vent through the sub-soil, through a concrete floor slab and into your bathroom/ D/Stairs WC. If you don`t have a sub-floor space then its a waste of time looking at the drainage system when it is obviously a venting problem
At a guess the sink/hand basin connects into a boxed in stub/stack shared with the toilet, on a line upstream of the main soil vent pipe, as a result when you flush the toilet there is a vacuum, which empties a sink trap.
There may be a boxed in air admittance valve which has failed, but raising it up 150mm will not help, NHBC will not help you out because this is due to poor construction.
Give the NHBC contractor a week. if you don`t get a satisfactory answer, notify NHBC/your builder that you will get a decent contractor in and pass the invoice on to them.
I suspect you may well be better off with a local plumber rather than a franchised drainage contractor.
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kdj
- Posts: 3
- Joined: Sat Feb 25, 2006 6:47 pm
- Location: essex
I am still having a problem with my downstairs toilet...
To recap - a cctv inspection was done, this showed no water retention was evident in the system and so it was therefore assumed that the falls were satisfactory. The conclusion was drawn that the problem is associated with above ground drainage due to lack of adequate traps, poor seals or lack of adequate ventilation. It was also noted that there does not appear to be any venting system to the downstairs wc.
NHBC fitted an anti-syphonic waste trap to the hand basin. this did not work. NHBC were so slow I got a plumber out who fitted another trap to the pipe further down and said it was unlikely that the 2 traps would be sucked out. Well, they both are because the smell is still present. It is only intermittent now, but it is still very strong and unpleasant when it happens.
NHBC came out again and have said they have no idea what it is. They suspect that the gradient of the pipe may not be steep enough, causing the temporary blockage of the pipe. When the blockage is dislodged, this is causing the suction that is sucking out the traps. This is BAD NEWS if this is so, as there is 10 metres of pipe under the house and the IC is just outside the back door...
Also - one day we had a very pleasant smell in the toilet - and we had not put anything down any of our sinks or toilets, so we have no idea where that smell was coming from...
Finally - the smell became apparent about a year ago, around 10 months after we had moved in - we didn't notice anything previous to this.
Anyone got any ideas - is the gradient of the pipe likely to be the cause, or is there something else it could be????
Comments appreciated!
To recap - a cctv inspection was done, this showed no water retention was evident in the system and so it was therefore assumed that the falls were satisfactory. The conclusion was drawn that the problem is associated with above ground drainage due to lack of adequate traps, poor seals or lack of adequate ventilation. It was also noted that there does not appear to be any venting system to the downstairs wc.
NHBC fitted an anti-syphonic waste trap to the hand basin. this did not work. NHBC were so slow I got a plumber out who fitted another trap to the pipe further down and said it was unlikely that the 2 traps would be sucked out. Well, they both are because the smell is still present. It is only intermittent now, but it is still very strong and unpleasant when it happens.
NHBC came out again and have said they have no idea what it is. They suspect that the gradient of the pipe may not be steep enough, causing the temporary blockage of the pipe. When the blockage is dislodged, this is causing the suction that is sucking out the traps. This is BAD NEWS if this is so, as there is 10 metres of pipe under the house and the IC is just outside the back door...
Also - one day we had a very pleasant smell in the toilet - and we had not put anything down any of our sinks or toilets, so we have no idea where that smell was coming from...
Finally - the smell became apparent about a year ago, around 10 months after we had moved in - we didn't notice anything previous to this.
Anyone got any ideas - is the gradient of the pipe likely to be the cause, or is there something else it could be????
Comments appreciated!
--kdj--
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danensis
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Tony McC
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This is another of those problems where we can but guess because we can't explore and examine the system at first hand. I know the NHBC rarely break into a sweat when it comes to these repairs, but if you were to speak to your mortgage company, their building surveyor might be able to exert more pressure on them to have the probblem more thoroughly investigated and a remedial strategy proposed.
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