Stopping strong wind sucking water out of shower trap

[tireetim]

I have an upstairs bathroom with a shower, a sink and a toilet. All connect in to an external soil stack which goes to a septic tank. I find that when the wind is strong (often is as I'm in the Hebrides) I get a strong smell of septic tank. I think this is due to the wind sucking the water out of the shower trap then the gasses getting in. Occasionally in the winter the wind is so strong it blasts the water out of the toilet U-Bend into the room but this is not often enough to really cause a problem. Can anyone advise me how to fix the problem? The top of the stack is open and not blocked although the top section (1m approx) is missing as it blew off but I will replace this although I think the problem was there before this broke.
Thanks.

 

[TheVictorian]

maybe a mushroom vent cowl or an external AAV?

 

[Gasguru]

External air admittance valve....Floplast AX110 might do the trick or a deeper water seal trap on the shower or a HepVo trap on the shower.

http://www.google.co.uk/url?sa=t&rc...Cs0OfxNj-Bh6Nvw&bvm=bv.62922401,d.d2k&cad=rja

 

[tireetim]

Thanks guys - I will try the AAV and if that doesn't stop it the HepVo trap.
Tim.

 

[Nige F]

Thanks guys - I will try the AAV and if that doesn't stop it the HepVo trap.
Tim.

So how is the septic tank going to vent if the vent stack only lets air IN The AAV might blow off in the wind anyway - speed bonny AAV , like a bird on the wing .........over the sea to Skye Go with the Hep V O - they can be fitted inline in a pipe run

 

[tireetim]

There are three vents on the septic tank then about 6m of 110mm underground pipe until it bend up and into the stack. Is this enough to vent with an AAV on the top? Just thought it might solve the problem of the toilet u-bend blowing at the same time. If it's not enough venting then I will go with the Hep V O.