Breather pipe/vent on sewerage pipes

Hi there,
Does anybody know anything about sewerage breather pipes - (the big pipe that sticks up in the air above the edge of the roof?)

I'm just asking because a house we're looking at buying doesn't have these, but has a vent in the pipe (near the facia, under the roof) instead. This looks a bit dodgy to me because there's lots of air vents in the facia, leading into the house, so surely the nasty smells & toxic gases could end up in the house? There's also a wall vent right beside the vent in the pipe.

It's a dormer bungalow, so maybe the reason they didn't put in a normal "pipe sticking up in the air" one is because there are windows for the upstairs just above it?

Can anyone tell me if this is ok or if it is dodgy?? I hope I'm explaining it clearly.
Thanks,
Tazaro

my half baked opinion: The breather usually only draws air in, as you flush a 'bolus' is falling down the pipe creating a vacuum behind it, the vent allows air in to prevent it drawing air through the toilet pulling the water out of your U bend and breaking the seal to allow smells into your bathroom.... true the vent is open to the foul sewer but there shouldn't be any large volume of gas being expelled out of the top, I think...

Building Regulations, Technical Guidance Document H refers. Foul water drains and stacks must be ventilated to allow gas to escape and to prevent the seals in appliance traps from being broken. Vents must terminate at least 900mm above any openable window. A ventilation branch pipe is acceptable but this must terminate a minimum of 900mm above a window where it is located within 3 metres of the window.

Thanks for the info. How does this work for a dormer bungalow where you have velux windows in the roof above the level of the vent? Would the vent pipe have to be REALLY tall?

If the pipe is within 3m of the window the 900mm rule applies- for this reason you'll often see the the vent pipe (or dry section of the stack) routed within the roof space and terminated in a vent tile ABOVE the window level.

I have two bathrooms in my bungalow, but only one 'stink pipe'.
Should there be two, one for each bathroom??

depends on the run of the sewer pipes. if their all connected to the same manhole or not etc. the vent pipe is to let the gas that has built up to escape. otherwise potential bomb! advice for smokers with no vent pipe in the system.......dont smoke while on the loo!!