P
Pzzszk
I am looking for advice/guidance on the re-design of the branch waste pipe run for a 1st floor basin. The starting point is the 35mm chrome pipe from the trap on the back wall of the house on the 1st floor. The end point is a pre-existing boss in the 4in cast iron soil stack located around the side of the house down near ground level. Normally I would use a McAlpine MS4-ISO 90 compression bend outside and then use 32mm welded pipe to get to the boss. There is only the one basin (no WC) connected to this branch waste pipe.
However, in this case, the waste pipe from the trap passes out through the wall and then needs to run 1.5m along an outside wall, then around a 90 corner and then down 2.4m to get to the level of the boss and then 1.2m across to the boss. So, a total of 5.1m (2.7 horizontal + 2.4 vertical) and 4 bends. If I read the regulations strictly, this isn't allowed without an additional venting (very difficult to achieve in this case) or a AAAV (even harder to achieve).
My questions are:
Do I need to count the vertical drop in the calculation? If not, then it becomes 2.7 and I can use 40mm pipe.
As this is one basin only (with a 35mm outlet), would converting to 40mm pipe after exiting the wall (about 6 inches from the trap) be sufficient to prevent the trap from autosiphoning?
Would it be better if I inserted a 60cm drop (in any pipe size) immediately upon exiting the wall, so that no water plug can be formed (basin only - no WC).
Would I solve (avoid?) all problems by just using 50mm pipe upon exiting from the wall?
Any help or advice will be appreciated.
Steve
However, in this case, the waste pipe from the trap passes out through the wall and then needs to run 1.5m along an outside wall, then around a 90 corner and then down 2.4m to get to the level of the boss and then 1.2m across to the boss. So, a total of 5.1m (2.7 horizontal + 2.4 vertical) and 4 bends. If I read the regulations strictly, this isn't allowed without an additional venting (very difficult to achieve in this case) or a AAAV (even harder to achieve).
My questions are:
Do I need to count the vertical drop in the calculation? If not, then it becomes 2.7 and I can use 40mm pipe.
As this is one basin only (with a 35mm outlet), would converting to 40mm pipe after exiting the wall (about 6 inches from the trap) be sufficient to prevent the trap from autosiphoning?
Would it be better if I inserted a 60cm drop (in any pipe size) immediately upon exiting the wall, so that no water plug can be formed (basin only - no WC).
Would I solve (avoid?) all problems by just using 50mm pipe upon exiting from the wall?
Any help or advice will be appreciated.
Steve
