fresh water drainage

[coolpaul]

Hi Folks,
I have moved into a property with a nice patio but I have noticed that the fresh water drain from the roof goes to the foul water manhole(I hear this common in older houses) but it does not seem to have a gully(trap). Is this ok. A friend said it should have a gully.
Cheers
Paul

 

[Ric2013]

Your friend is right.

 

[coolpaul]

Cheers Ric, I would have to dig up the patio. Is it essential or would it be possible to put the gully in the manhole. Hope this does not sound stupid.

 

[johnduffell]

You have to either replace the gulley with a trapped one or you could put it somewhere later on the pipe between it and the manhole. Usually you'd put it at the gulley because that provides a handy access for clearing blockages and silt.
You wouldn't get away without digging things up but it wouldn't be a big job for someone experienced.

 

[coolpaul]

Thank for the reply John, news I did not want to really hear but if it has to be done. I suppose there is no wee miracle adapter that you insert into the drain that does the same job eh. Ah well where's that kango. Cheers.

 

[Ric2013]

As a workaround, could you make a reasonably airtight connection between the gulley and the drainpipe, and then add a waterless trap that would fit into the drainpipe itself. A HepVo would work, but it wouldn't fit and I think the largest size is 40mm.
Anyone aware of something he could use without digging up the patio? I know traditional water seals are reliable and preferable, but the bodge has already taken place...

 

[coolpaul]

Cheers Ric there may be hope yet.

 

[johnduffell]

Ric has a great idea and you might be able to just class the gutter as some kind of rudimentary vent pipe! Therefore not needing trap.
I'm not sure hepvo would cope with the moss and birds nests from the roof.
If you're not noticing smells you might be able to get away with it for now, see how it goes. But if you find a powerful stench in the loft, maybe not.
If the loft does get smelly you could add a hopper part way up to release the smell away from the eaves.

 

[Ric2013]

That's a point. If the top of the drainpipe is a reasonable distance from any opening windows such that the foul air doesn't come into the house (building regs would be 3m horizontally, but you may get away with less), then it could well act as a vent pipe if you seal the bottom.

 

[coolpaul]

Sorry folks I dont think I explained myself too well. Please see diagram. Cheers

 

[Ric2013]

My point about sealing was that you could possibly modify the 'drain pipe from roof' to seal to 'drain' from your diagram. The opening to atmosphere would thus no longer be at ground level but at a hopper, if there is one, or at the gutter. Where would that opening be, relative to windows?

Your diagram confirms what I thought your text was explaining: no surprises 🙂