I'm in the process of building a large garage at the end of my garden that will contain a toilet. Do I need a vent stack at the garage end as well as the house end? The toilet will be approx 30meters from the existing vent stack.
Youcould use one of these maybe! http://www.screwfix.com/search.do;jsessionid=ZTQEXJJ1EZ3M2CSTHZOSFFI?_dyncharset=UTF-8&fhsearch=Air+admittancevalve&x=12&y=10
if you are running the foul drain from the new wc into the existing system that already has a vent stack then no vent stack is needed at the garage. would suggest an unvented stub stack tho, to allow connections from sink. this will give you rodding access also. the AAV suggested earlier may not be a good idea as they are not generally supposed to be in unheated locations as they are susceptable to frost
As the new w.c. appears to be at the head of a single line the answer is yes. The purpose of a vent stack is to save the trap from being pulled out with the outflow with the resulting problem of drain stench in the toilet. It stops a syphon from forming. It does not need to be an actual open stench pipe, as you could use a vent (durgo valve is one name I believe) which allows air in but seals to stop the smell getting out. Bottom line is you definitely need something but it is your choice as to what. If the new run is a straight line you do not need rodding access as you would rod back from the manhole that you form where you join the new pipe to the old. Having said that, if you fit a vent stack as against a one-way valve you could easily incorperate a rodding access at very little cost by fitting a T and a blanking plate.
yes you do need some form of vent to this drain as it is so far away from the existing one. an automatic air adittance valve would be ok for this but I would advise you to box in the pipe and wrap it with cosywrap or similar. obviously you do not cover the valve itself and you will need to fit a vent to the box to admit the air. as for rodding back from the manhole this is wrong. you must provide a rodding access and make sure you have at least a 1 in 40 fall. the idea of rodding is to send the obstruction down the drain not up it!!
Sorry to correct but if the run is straight then rodding back <u>from</u> the manhole is permissible.