MAN-HOLE VENTILATION SYSTEM

[J0hnny]

Dear all,
i wonder if you can help me. We currently have a public sewer/ man-hole right in the entrance to our development, 12m deep with a 3.1m diameter combined attenuation facility at the bottom. When it rains the pressure is such that it blows the lid. I have approached the water authority and they have accepted that it's their responsibility to vent the MH. However their timescales to carry out the work is not accommodating the opening of the development. i therefore need to install temporary measures. In order to minimise smells etc when pressure is low I think a valve of some sort would be appropriate (prob need to be 300 diameter given the pressures). However I do not have much experience in ventilated MH's. Can you advise please? many thanks for your help as always. Kind Regards

 

[elev8848]

JOhnny:

IF the concern is that the MH lid gets blown off by pressure of air or water, a manhole cover with a hinge is available.

IF the concern is odor, a diaphragm (a thin light circular metallic disc) is available that is installed directly below the manhole cover. But if the ventilation is needed to allow for pressure fluctuations within the sewer, this option might not be allowed.

 

[J0hnny]

Thanks for your response. The problem is both....I want to prevent the man-hole from surcharging, relieve the pressure during storm periods and keep the odour to a minimum. Due to the man-holes location and need to re-direct the pressure to a verge via a valve system i think? the traight forward thing to do would be to fit a stack to the man-hole but this is not partilcularly convenient at this location.

 

[LCruiser]

This is apparently a combined sewer? If the manhole lid is blowing during storms I would seriously look at the pressure back up the line to the development. Otherwise a locking manhole might be a fix with an air-vac to prevent water from escaping.

 

[J0hnny]

Yeah it's a combined sewer. it runs from a 675 diameter pipe into a 3.1diameter pipe where the flow is then attenuated - I need advice on ventilting the man-hole so that pressure can be controlled to prevent surcharging - many thanks