Outside sewer vent covers

[Andrew Gabriel]

I know they aren't fitted nowadays, but situation here is a sewer with an intercepter trap manhole at the end of the run before it goes into the main street sewer. This has a cast iron vent pipe into the manhole which comes out of the ground nearby and rises up a low wall with a vent on the top with a rectangular slatted face, except the face has long since gone and it's just wide open to the sewer. It often smells.

I have something identical on the outside wall of my house so I can see what's meant to be there - the slatted grill has a thin flap (looks like mica) behind it which acts as a one-way valve to let air into the sewer, but not out, presumbly to prevent pongs, and this one seems to work - it's quite near the living room window, and has never smelt. (This one will be 1909, and the broken one is 1920's but what's left of it looks identical).

Any idea if these vent tops are still available? Couldn't find any, but not sure if they have a special name? Don't think a modern plastic one would survive near ground level next to a footpath.

[newshound]

Don't see why thickish plastic sheet (say 200 to 500 microns) should not behave in much the same way as mica. The sort of thing sometimes used for covers of reports. I wonder if the mica sheet just flexes or whether it is hinged (and perhaps sprung). This is assuming you can get "inside" of course. But it *is* DIY!

Alternative I suppose might be just to hide a modern air admittance valve in a suitably disguised metal box. If you have decent access to the CI pipe which is presumably ~ 120 mm dia perhaps you could cut the box off, insert waste pipe plus air admittance valve down the upstand, and pop the "box" back on the top.

[DerbyBorn]

newshound wrote in news:509a52b7$0$14959$c3e8da3 $ [e-mail]:

I wonder if it is now required. The need for these seems to have reduced over the years and many sewers are only vented at every 2nd house (I think). Is is a shared branch? If so, under the new regulations it will now be adopted by the relevant water authority.

[Andrew Gabriel]

It's vented because it's an intercepter trap. These aren't used anymore AFAIK, but I presume if you still have one, it still needs to be vented. OTOH, the intercepter trap is defeated by the rodding plug having gone missing.

It is shared by 6-8 houses, and yes, we could call out Thames Water, although when it blocked some months back, I rodded it myself. Got enough fat out to fill a few carrier bags.

[Hugo Nebula]

Theoretically, yes. However, there are probably enough open stacks on the sewer to make it irrelevant. In my home town at least when 'grant work' was carried out in the 1970's & 1980's, the drainage systems were renewed & interceptors removed.

The point of interceptors was as the only trap between the sewer & the house, as there were usually no traps to any fitting within the house or the yard. Now every appliance is trapped, and all yard gullies are supposed to be too, so there's no need for interceptors.