Soil pipes and stuff

[David WE Roberts]

We are looking at extending out at the back of the house. This would involve building over a run of soil pipe from the stack to the first manhole if we don't relocate stuff. I have had a brief trawl through the Building Regs and it looks as though we are O.K. as long as the first run of pipe does not appear on any sewer maps. Other hpuses along our row have already done this so traditionally there wasn't a problem. However it would be good to know that this is O.K.

We are also going to build a new downstairs shower/toilet in the middle of the house. I am assuming that we don't need a soil pipe but can manage with a one way valve. However, I don't yet know how far the one way valve has to be (vertically) from the toilet itself.

Any advice welcome.

Cheers

Dave R

[Tim Watts]

??? Don't understand... Unless you are installing a macerator, how are you going to manage without a soil pipe?

I have a bog in the middle of the house with the soil pipe under the floor - I have no one way valves. Do you expect back flooding from the sewer?

[Tim Lamb]

In message , David WE Roberts writes

We have several runs of soil pipes crossing our house. Two are sandwiched between the oversite concrete and the floor screed. A concrete lintel carries the wall above them. The 3rd is deeper and passes through the foundations of an extension. Again, protected by a concrete lintel.

Rodding access is a consideration. The other issue we found is that drain trenches must not be deeper than a line drawn at 45deg. from the bottom of the building foundation. Not a problem for a right angle crossing but tricky when parallel.

Is this a *stubby stack*? I have a similar job to do and eagerly await the responses:-)

regards

[David WE Roberts]

Sorry, lack of clarity. Should have said soil stack. Old style, you hacve a soil stack which opens to the air above the house and away from windows etc. New style, you can have a stack which terminates inside the house and has a one way valve to let air in but not sewer gasses out. AFAIK you have to be able to let air into the end of the run of soil pipe to prevent siphonage of the U bend. Just wondering how tall the internal soil stack has to be. It would be nice for it to be discreet.

[David WE Roberts]

A stubby stack was what I was imagining - the question being how stubby can you get?

The extension will be single storey so no great load. The current soil pipe is where the side wall would be, so if it stays I presume we build round it. Need to go and chat to some neighbours. The short run of pipe would be diagonally under the floor to the back, and the rodding arrangements would not change - there is no rodding hole in the stack and access is from the manhole at the back of the house. The iron stack would be replaced by plastic as we have to re-route the bath and shower into the soil stack as they come down into the centre of the back of the house ATM.

The new horizontal soil pipe would go from the centre of the house to the side where the drains run from the back of the house out to the road. I am assuming it can go under the suspended wooden floor and out through the foundations and not above the floor along the wall and straight through the kitchen. Another issue to sort out :-)

One option is to dispense with the old soil stack completely and relocate the bathroom outlets to the centre of the house above the downstairs toilet and put everything one one new pipe. However this does limit our options a bit because there isn't much overlap between upstairs and downstairs bathrooms.

[Tim Watts]

ah - then what you mean is called an "AAV" or Air Admittance Valve.

A one-way or non return valve implies a different beastie that is used to prevent backflow and flooding from the main sewer.

a look down the last few pics in the above album ^^^

The lumpy grey thing on the left in the boxing-in is an AAV. Specifically it is a Floplast AAV that is designed to be installed below the flood line (the sink typically, or the top of the pan depending on what feeds in.

There is a min height above the pan connector - the full details are here:

(hunt around for the leaflet or data sheet - mounting details and diagrams are in there).

But, typically it means this particular AAV can be mounted so its top is more of less at the level of the pan/bog seat which makes for neat boxing in.

Another possibly acceptable solution is to use a HepVO valve in the run to the basin and use that as a method of venting the soil branch.

Personally, I like the Floplast - do not substitue to another manufacturer, usually AAVs have to be installed much higher. But the Floplast is readily available and cheap. It's fairly quiet in operation - slight "blurp" - I've heard much worse ones (massive "farty" noises when letting air in).

Cheers

Tim

[Malcolm]

When we had an extension built it went ove a foul water sewer and a surface water sewer from next door. All that was required was lintels where the pipes passed through the foundations for the walls. There were joints (in the plastic pipe) which would have been in the middle of the extension so, being ultra cautious I made sure that there was a jointless run of pipe under the extension

Malcolm

[Man at B&Q]

It has to be higher than the highest water level. If, e.g., it's below the level of the washbasin and the whole system gets blocked, with a basin full of water, when you remove the AAV the head of water in the basin may force "stuff" (not neccessarily just water) out of the top of the AAV.

MBQ

[Tim Watts]

That is generally true - but if you refer to my message of a couple of days ago, the Floplast does *not* have this requirement, which makes it ideal for the OP's application ;->

[RobertL]

I'd be surprised if it made it OK just because it isn't on the sewer map. It might well be a public sewer; if it was built before 1937 (IIRC) and serves more than one house then it is IIRC.

With Thames Water (for example) you need to get their agreement if you build within 3 metres of it or over it.

[David WE Roberts]

I'd be surprised if it made it OK just because it isn't on the sewer map. It might well be a public sewer; if it was built before 1937 (IIRC) and serves more than one house then it is IIRC.

With Thames Water (for example) you need to get their agreement if you build within 3 metres of it or over it.

*************************************

Then again it might not be as it only serves one house. Have you read the relevant part of the Building Regs? It was very specific about the sewer maps.

[Jethro]

So looking at that, I could replace the hideous eyesore we have had since moving in (about 10' high, and "S" bending around the eaves) with a 5' pipe and external AAV ?

What's the best way to replace a cast iron pipe with plastic, regarding joining below the ground level ?

How much can I get for about 100Kg cast iron ?

[docholliday]

It's a pity the people who extended my parents' house (before they bought it) were'nt equally cautious. Not only are there lots of joints

- they couldn't really avoid that since this was before the days of plastic pipes - there are also two manholes inside the extension, one of which is at a near right angle bend in the pipe...

[Tim Watts]

If you have 5' above the eaves, why do you have an AAV? Are your sure - such pipes are normally open to air.

Assuming I'm right, you may or may not be able to replace it. Under some conditions, you *should* have an open to air vent on the furthest branch of your local drain so it can vent postive pressure (AAVs only vent for suction). You'll have to look at the building regs, part-whatever-drainage is.

Wait for someone else, no idea....

If the merchant is near, some beer money. If the merchant is miles and miles away, I'd just leave it for the pikies because I;m lazy like that...

[David WE Roberts]

Ummm....... As I read it, the current pipe does not have an AAV.

[Jethro]

No there's no AAV. The current cast iron stack is about 10' high and looks ghastly.

Since we get at least 3 scrappies a week driving round, the physical removal is not a problem. I just wondered if it was worth anything ...

[Tim Watts]

Oh yes, you're right. I misread: "and external AAV"