Period Chill

[plasticpigeon]

We've had quite a bit of snow in the Midlands. The combination of pretty good roof insulation and no central heating means that we have had twice as much snow on our roof as other houses on our street. That is until most of it slid off and took the guttering with it!! On the last picture the gutter has completely fallen off leaving only the bit by the downpipe!

 

[DJH]

Oh dear, more work then plastic..... Is that an Automatic Air Admittance valve on your soil and vent pipe? Do they work outside nowadays?

No snow here........

Doug

 

[Penners]

Yup - looks like a Durgo valve to me. They can definitely be troublesome in very cold weather - they're best fitted indoors.

 

[plasticpigeon]

I haven't a clue about the soil pipe, I didn't do the system. I guess that since top of the pipe is low it would not be nice to have just an open vent, if that is what normally sits on top of a soil pipe. No troubles so far, how would the troubles manifest themselves? I am planning to redo all the drainage this year, as it was lined and generally cocked around with under an insurance claim not long ago (made and executed before I bought the house). If the drains are as badly repaired as the rest of the insurance work on the house then they will probably be worse than they were before the work and need remedial work.

 

[MdB]

No troubles so far, how would the troubles manifest themselves?

If it sticks open then smells outside.

If it sticks closed then gurgles in the wash basin / bath when you flush the loo. If its bad enough, it will remove the water from the U bend and you will then get smells.

 

[Penners]

how would the troubles manifest themselves?

An air admittance valve or Durgo valve works by allowing air in, but not out. So it prevents the traps in your plumbing system "pulling" when you flush or drain a bath, etc., while preventing nasty smells from being emitted from the soil pipe.

A soil pipe that extends up beyond the eaves is not usually fitted with one, as these unpleasant smells are simply dispersed before they can enter the house. But your soil pipe terminates at a surprisingly low level, which is - I imagine - why the plumber fitted a Durgo valve.

The problem with exterior Durgo installations as that they can freeze up. In such cases you can usually smell the problem! However, some models are fitted with internal insulation which is usually (but not always!) a reasonable protection against freezing.

 

[robgil]

Sometimes a sewer needs venting to atmosphere as well , if the vent is sealed it could cause sewage smells to escape through your water traps. If that were mine and it was not vented anywere else I might extend it and put a rain cap or 90 bend on the top. (can you still use elbows on the top of vent pipes? The drainage firm who put mine in seems to think so).

 

[DJH]

In addition Penners these AAV's are required to be higher than the lowest water waste trap in the particular situation that soil pipe serves. This usually is the waste trap in the wash basin although from memory the manufacturers want them the same height or higher than the level of water in the toilet cistern even though that has no influence on the operation of the valve. They are, unless as Penners says insulated, designed to be installed indoors and should not be fitted if the soil pipe is the only form of ventilation to the drains.

In other words the simple rule is that if a drain from a manhole has only one soil and vent pipe serving it then that vent should be open to the air and not have an AAV fitted. If there are two or more vents fitted to the drain then the lower ones can have an AAV fitted but the vent at the top of the run should be left open. This particular situation tends to happen more in terraced houses but large houses may well have more than one bathroom each served by a separate soil and vent pipe.

If an un-insulated AAV is used externally the rubber foo foo type valve which, because of it's position at the top of the pipe, will more than likely be wet from condense in the pipe from hot water, will freeze and could stick to it's seat and not allow air to enter. What can happen in this case is that if, for example the bath is emptying and the wc flushed at the same time a vacuum could be formed inside the pipe which, because the AAV is stuck, could siphon water from the waste traps on other sanitary fittings allowing foul air into the rooms the fittings are situated.

Another consequence of AAV's failing is that with no fresh air available in the drain all sorts of nasty things have an ideal environment in which to flourish. Believe me I've seen this gunge and I would not care to have it invade my house especially if one of the traps that was 'pulled' is in a basin in a bedroom.

Anyway this is from my experience in the plumbing industry. I'm sure the present regulations are the same as they were in my time.

Doug

Sorry Rob your post got in first!!

PS I would hazard a guess that somebody put an AAV there t save extending the pipe upwards at least on metre above and away from an opening in the house. Perhaps he was afraid of heights :roll:

 

[plasticpigeon]

Thanks or the advice. I plan to change the whole system in time.

 

[Penners]

In which case, PP, if it were mine I would just extend the soil pipe up above the eaves and leave it with an open top (except for a bird guard). Simple is best - nothing to go wrong!

 

[Lime]

I noticed the air admittance valve too and agree with the advice that a simple open ended vent pipe with bird excluder is wanted.
You will need to glue the pipe between the two pipe joints where you negotiate around the eaves as a strong wind may catch the top of the pipe and cause the pipe to pivot at this point.
(This assumes the pipe above the eaves is free standing. If it is supported you do not need to worry about the wind)
You can use a smaller diameter vent pipe than 110mm too.

 

[DJH]

The neatest and most secure way of extending the vent is to take it straight up through the soffit and the the tiles and weather it with a lead slate. Didn't I use to make those things...

Doug

 

[Lime]

The neatest and most secure way of extending the vent is to take it straight up through the soffit and the the tiles and weather it with a lead slate. Didn't I use to make those things...

Doug

If you look at the pictures the eaves have little or no overhang save for the guttering.
Going through the eaves isn't an option in this case.

 

[DJH]

Yes you're quite correct Lime. Sorry everyone I just didn't look at the picture properly, but in my defence when there is a soffit its the better way of doing it and you get to use some lead as well.

Doug, off to Specsavers

 

[DJH]

PP you could reduce the size of the vent part of the soil and vent pipe to 3" or 75 mm if you wanted too but I always think the change of size draws they eye towards it as it's not the usual way when the stack is located outside for some reason. As Lime says you should use solvent weld joints on the offset bends, (45 degree ones are best) going around the guttering and I would suggest that you clip the upright pipe to the wall as close as the top bend will allow you. This will increase stability against strong winds.

Doug, no snow here

 

[Zebra]

Remember this everybody? Remember bedsocks and hot water bottles and icicles and snow on the roof and minus 13 in the morning? Isn't it nice now that it's warm?

 

[angrybird]

it doesn't seem that long ago that it was minus 15 and a metre of snow!
today it was 30 degrees, not quite hot enough to fry an egg ...yet :roll:

my poor Malcolm (car) buried in the snow

 

[Penners]

Isn't it nice now that it's warm?

It must remind you of your happy days in the Serengeti.

 

[Zebra]

Ah, happy days indeed.

 

[Penners]

Well look at you, camera-hogging right in the middle. You'd had your mane and hooves done specially for the photoshoot, hadn't you?