Gradient limits on branch pipes ?

[1justin]

Part H table 2 & diag 3. Gradient limits for unvented branch pipes.

I understand the reason to put a maximum gradient on - to avoid unsealing traps.
(eg washbaisin on 40mm can achieve maximum of 3M on 18mm/M)

Is is correct to assume that if the pipe must turn completely vertical for part of a run before the stack, then that's not exceeding the guideline?

 

[Hot&Cold]

Part H table 2 & diag 3. Gradient limits for unvented branch pipes.

I understand the reason to put a maximum gradient on - to avoid unsealing traps.
(eg washbaisin on 40mm can achieve maximum of 3M on 18mm/M)

Is is correct to assume that if the pipe must turn completely vertical for part of a run before the stack, then that's not exceeding the guideline?

That looks like a question i composed for an exam centre,i remember it was not policy to include the words,
Hello
please can i ask
Thank you for taking time to read my post

1justin
Please refer to your reference material,the answer is there but consider many installs are sui generis and the rule of diversity applies.

If in doubt on site ask the building control bod who has to sign off the work.

 

[John D v2.0]

Is is correct to assume that if the pipe must turn completely vertical for part of a run before the stack, then that's not exceeding the guideline?

It's a common misconception that vertical doesn't exceed the fall required but vertically is actually infinite gradient and if the sink outlet drains quickly enough you'll hear the trap sucked as you empty the sink.
The principle of waste pipes is t the pipe should never completely fill with water IE surcharge, there should be space for air to come the opposite way up to pipe.
To do it properly you need to run the waste into a 50mm stack and drop it down that way. Then you won't hear any traps siphoning.
Alternatively you can get one of those naff IKEA sinks that drains slowly anyway then it won't fill the pipe.
The other alternative is to put an aav behind the sink or install a ventilating branch if you're that way inclined

 

[1justin]

Thank you John. That was how i was seeing it, hence posing the question. So in principle, if the 40mm were full, then a 50 won't be (at least initially), hence going up a size for the vertical bit would suffice. That could work for me.
(Old&Bold, your humour is one step beyond my ability to understand WTF you mean, despite checking your Latin, but thanks for the reply

 

[John D v2.0]

Yes basically up a size should do fine. Just have regard for the size of the trap and the peak water flow.
I did 50mm for the vertical pipe from upstairs to down, but the very short runs I got away with trap size because one is a shower and the other is a basin from IKEA. A bath would be more critical than a shower.
Sounds like you understand pretty well