Posted: Wed Jan 14, 2015 1:18 pm
I need to make a fall of about 6m over a distance of 34m, to connect my house to a new septic tank system.
I'm aware that there are regulations covering minimum gradient, 1:80 I believe, but I can't find anything about a maximum gradient. It has been mentioned to me that beyond a certain gradient you risk 'stranded solids' however I cannot find what that magic gradient might be, and any attempts to google it simply turn up people declaring the whole thing to be a myth anyway, suggesting you can go for whatever gradient you want.
I did email my BCO but he only said to keep the fall into the tank at 1:40, and use backdrop manholes. I can understand that the final flow into the tank needs to be at a low rate, but I don't see why it matters what I do upstream of that.
Part H has tables showing flow rates starting at 1:10 which whilst not stated as being any sort of limit at least implies that you can go that steep.
If I can go to 1:6 or so then it will save me a lot of hassle building backdrop manholes.
Cheers
I'm aware that there are regulations covering minimum gradient, 1:80 I believe, but I can't find anything about a maximum gradient. It has been mentioned to me that beyond a certain gradient you risk 'stranded solids' however I cannot find what that magic gradient might be, and any attempts to google it simply turn up people declaring the whole thing to be a myth anyway, suggesting you can go for whatever gradient you want.
I did email my BCO but he only said to keep the fall into the tank at 1:40, and use backdrop manholes. I can understand that the final flow into the tank needs to be at a low rate, but I don't see why it matters what I do upstream of that.
Part H has tables showing flow rates starting at 1:10 which whilst not stated as being any sort of limit at least implies that you can go that steep.
If I can go to 1:6 or so then it will save me a lot of hassle building backdrop manholes.
Cheers
