Two 90 degree bends from toilet to soilstack, bad idea?

[CortinaV8]

Ideally I would like to relocate my bog to another wall in the bathroom, this would involve using a 90degree elbow straight off the back of the pan, through the wall, another 90 degree elbow then about 2.5m of pipe before it reaches the soil stack.

I can get more than the required level of fall however is it a good idea? common sense tells me no, but there must be thousands of them installed like this.

 

[Richard C]

Not a brilliant idea as adjacent elbows will be prone to blockages; any chance you can fit a slower bend to the second? B Regs also require that you provide rodding access for clearance of blockages to all bends greater than 45 degrees but that shouldn’t be a problem on the outside. I tend to stick with 1:40 (25mm per metre) fall; you can go to 90mm per metre but the problem with going too steep is the water tends to run away quicker than the solids increasing the risk of blockage.

 

[mysteryman]

It should be OK if you keep the fall. I've done the same, and mine go through at least three bends before the stack.

However, as above, it may not be legal.

 

[Richard C]

It should be OK if you keep the fall. I've done the same, and mine go through at least three bends before the stack.

It’s not the number of elbows in a run that’s particularly a problem, it’s having two of them very close to each other other.

 

[mysteryman]

Mine's been OK for a couple of years now.

 

[CortinaV8]

Any more thoughts on this? Distance will be about 70 cm between points? How close is too close?

 

[Hugh Jaleak]

Elbow at the back of the pan should be fine, must be thousands of pans fitted like that. The other elbow where the soil pipe passes through the wall, fit an access bend so you can get inside the pipe should worst happen.....

 

[Richard C]

Close-ish but could be worse. Problem is that flow slows dramatically when it hits a sharp 90 degree bend, OK; but stick another 90 degree bend in there before everything has had a chance to get up velocity again & the solids will sink while the liquid will continues on. Hydraulic flow is a complicated science, it’s a bit like having too much of a fall on a straight foul drain, you need the liquid to accelerate at a low enough velocity to keep the solids flowing with it, too fast & they will stay put. That’s why I suggested a bend rather than an elbow on the 2nd; 70cm should be OK but much depends on the size of eggs you lay ; just make sure you have a rodding hatch.