Soil pipe Gradient

[Hydra]

Quick question as I note in part H of the building regs it makes specific mention of the minimum gradient of a pipe run. 

 

 

Currently I have some workers putting in a soil run that's going to be more like 12-15 degrees, which I believe is something around 1:4 - 1:5 gradient. 

 

From what I read online for advice this isn't ideal - My groundworkers insist they don't have any choice (think they want to avoid a backdrop)

 

Any thoughts as I have Mr inspector round Monday and the groundsmen will be long gone by then. 

 

Update - yes i've contacted regs, but after they haven't responded to my last 7 emails, i've given up with getting any advice from them. 

 

Cheers

Edited July 15, 2021 by Hydra

[Ian]

There’s nothing in either the British Standard or in the Building Regs that stipulate a maximum gradient so you’ll be okay when the inspector visits.

[MikeSharp01]

8 hours ago, Ian said:

There’s nothing in either the British Standard or in the Building Regs that stipulate a maximum gradient so you’ll be okay when the inspector visits.

+1

[ToughButterCup]

1 in 2 for 5 yards.  " ... (think I want(ed) to avoid a backdrop) ..." BCO: no comment

 

 

The whole foul drainage system needed 31 cubic meters of  top cover dug by hand during the first lockdown.

Oh dear, what a shame, never mind. I had nowt else to do.

[George]

I've never heard of an issue with too steep a gradient. Soil pipes start vertical after all!

 

Backdrops are preferred because it minimises excavation - but you do need to have the right components available.

[joe90]

1 minute ago, George said:

I've never heard of an issue with too steep a gradient.

It used to be said that too steep a gradient could lead to fluids flowing fast and leaving solids behind, but I think this has been re assessed hence it is now not of concern.

[ToughButterCup]

My BCO suggested we connect one short bit of rain gutter to the foul drain to provide a small amount of flush to the  pipe. Works well, I think.....

[tonyshouse]

One niggle, manhole/inspection point needed at each change of direction 

 

even fall is best 

[Hydra]

4 hours ago, George said:

I've never heard of an issue with too steep a gradient. Soil pipes start vertical after all!

 

Backdrops are preferred because it minimises excavation - but you do need to have the right components available.

 

6 hours ago, MikeSharp01 said:

+1

Unfortunately not the case, just got off the phone with the BCO and he said he won't accept more than a 6cm drop per meter. (1/60)

Which leaves me feeling a) slightly peeved, and b) Slightly happy about being a first for something. 

Now I either need to go outside and dig another 1.2 meters down, though nothing but stones and clay for 6 meters, or use a backdrop which would mean the pipe would be about 4 inches under ground level for half the run, and will be smashed to pieces when I have a driveway put in next year.

Potential solution,  Perhaps i'll get the initial run a little lower using a stub stack, then a backdrop at the end. To at least get it low enough that I can actually put soil over it!

 

Thanks for all the replies and sorry to be the odd one out with his BCO. 

 

 

[MikeSharp01]

19 minutes ago, Hydra said:

Unfortunately not the case, just got off the phone with the BCO and he said he won't accept more than a 6cm drop per meter. (1/60)

Hmmm sounds odd - did they explain their reasoning? Also 6cm / Meter = 1 / 17 while 1:60 is between the BR 1:40 and BR 1:80 

[ToughButterCup]

39 minutes ago, Hydra said:

... Unfortunately not the case, just got off the phone with the BCO and he said he won't accept more than a 6cm drop per meter. (1/60) ... 

 

What an arisole.  What gets me is that it's so arbitrary.

[Hydra]

40 minutes ago, MikeSharp01 said:

Hmmm sounds odd - did they explain their reasoning? Also 6cm / Meter = 1 / 17 while 1:60 is between the BR 1:40 and BR 1:80 

 

Possible that i've misquoted him with my 1:60! He stated for every 1m of run, 60mm was the maximum he would allow for drop. (for foul drainage). His reasoning being any steeper would leave the solids hanging dry. 

 

Given the dislike for steeper gradients I wonder if he will dislike my stub stack! (joking) 

 

Asked for a written conformation to present to my groundworkers, who aren't that happy, and in their own words "are too old for this"

Edited July 16, 2021 by Hydra

[Mr Punter]

Ask him where it says that in the regs or what standard he is working to.  BS EN 752 only refers to minimum gradients as do all the warranty providers.

 

The only time steep gradients are an issue is with systems with slotted pipe to allow infiltration to the ground and systems where you need to control the velocity before entering a treatment plant.

[Hydra]

1 minute ago, Mr Punter said:

Ask him where it says that in the regs or what standard he is working to.  BS EN 752 only refers to minimum gradients as do all the warranty providers.

 

The only time steep gradients are an issue is with systems with slotted pipe to allow infiltration to the ground and systems where you need to control the velocity before entering a treatment plant.

 

Have asked for written clarification but as the work is being done tomorrow, doubt I'll be hearing back in time. Gulp! 

Next time in life i'll leave all the reg interaction to the builder rather than pretending i'm a project manager  

 

[joe90]

Just read the regs and no max slope quoted, just minimum slopes (unable to cut and paste it for some reason?) why not challenge your BCO to quote the regs where it says max slope ? 

 

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/442889/BR_PDF_AD_H_2015.pdf

H1, page 16 table 6.

[markc]

I reckon he/she is very old school and referring to cast iron or clay wastes. (the rough inside face do tend to leave solids behind).

[ToughButterCup]

Could I suggest you let the ground workers  -just-do-it- and if the BCO wants to sound off later, then fine (for the reasons explained above).

I have had several interactions with BCOs where their comments have no basis in guidance or common practice: but have adverse consequences for me.

Now I have taken to asking the BCO -while still on site- to agree my notes and action points before he (or in one case she) leaves the site.

 

That process seems to work well. Exactly the same process as managing your own line manager.

[saveasteading]

I believe the regs have been simplified...although I am not about to look up the old books.  There was once a rule, or at least understanding, that there was a maximum gradient to prevent separation as described. That of course does not apply to vertical stacks as obv it all just falls together. 

Also it is a fact that there can be separation, but it may now be recognised that another train will soon be along to give it a shove.

Diagram 9 stops at gradient 1:10, so it could be argued that this is the maximum.

 

AND it used to be that every change of direction, horizontal or vertical, required an access chamber. That has been dropped.

Well, not dropped exactly: it now says 'as straight as practicable, so that does leave it up to the inspector.

So be happy that he is ok with it , as that is not as straight as it could have been.

 

If the groundworkers are too old to remember these old rules then they aren't really very old at all, or were not paying attention.

 

In reality, your  arrangement with the steep section, rather than a simple grade, will work fine.

Did you say why they didn't do a constant grade?

 

I tell BCO if I disagree: Some are happy to agree when they hear the argument or see the proof. Some get very angry indeed to be shown to be wrong, and then it is time to demand someone else, usually younger.

BUT to their credit they come across some awful work, where the builder does not care or understand the theory. Perhaps they have to assume we are all like that until proven otherwise.

 

47 minutes ago, ToughButterCup said:

asking the BCO -while still on site- to agree my notes

Yes, this is management, even teamwork, and has the least chance of causing disagreements.

The BCO is not a designer, and neither, usually,  is your groundworker.

 

[Hydra]

1 hour ago, ToughButterCup said:

Could I suggest you let the ground workers  -just-do-it- and if the BCO wants to sound off later, then fine (for the reasons explained above).

I have had several interactions with BCOs where their comments have no basis in guidance or common practice: but have adverse consequences for me.

Now I have taken to asking the BCO -while still on site- to agree my notes and action points before he (or in one case she) leaves the site.

 

That process seems to work well. Exactly the same process as managing your own line manager.

Yes I have been giving them written plans of my intended methods for almost all works, to keep them sweet. I dare say some of it is architect standards as I had far too much time during lockdown.

Unfortunately this time, disaster. Came home to find the work has done, the pipe is cut and measured and fitted (no infill yet thankfully) but the gradient is a 6 inch drop per meter.
The problem being in the same evening I have in writing from the BCO confirming the absolute maximum the he will accept is 2.5 inches per meter. 

Groundsmen understandably are peeved, as it passes regs in their eyes. Maybe I just get them both a table for two and tell them to hash it out?

Anyone had a similar mexican standoff ? Wondering what's best to do. Other than revert to forums to moan about my issues 

 

Once again thanks for the views and such. 

 

 

[Hydra]

I don't get it, if 1:40 is the optimum for flow - why am I being asked to do 1:60! So confused... 

 

 

[Oz07]

1 60 is more like 18mm. I've laid at 12 before now. 

[Temp]

 

26 minutes ago, Hydra said:

I don't get it, if 1:40 is the optimum for flow - why am I being asked to do 1:60! So confused... 

 

 

 

Welcome to self building! Someone should have told you that managing people is the hard part. ?

 

Given a choice I would keep the BCO happy rather than the ground workers. You might need the BCO to be more flexible later. So I would try to meet his 60mm per meter maximum if you can. 

[saveasteading]

If that is your decision, then show the groundworker diagram 9 and clauses 2.19  and 2.20 of document H.

Any change of gradient to have an access point. They have none

Bends as large a radius as possible. They have tight bends.

Unfortunately I can't screen grab it, but here is the link

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/442889/BR_PDF_AD_H_2015.pdf

[Hydra]

22 minutes ago, saveasteading said:

If that is your decision, then show the groundworker diagram 9 and clauses 2.19  and 2.20 of document H.

Any change of gradient to have an access point. They have none

Bends as large a radius as possible. They have tight bends.

Unfortunately I can't screen grab it, but here is the link

 

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/442889/BR_PDF_AD_H_2015.pdf

Hmm thanks for pointing these out. Have read through but didn't notice the specific points. 

 

They did install, to my relief - an access chamber via a plastic manhole at the start of the drop, just out side the property. 

 

As for the lowest radius possible, i'm assuming by avoiding a backdrop they have technically achieved this? 

 

Currently the run has a slow 90 on the internal, a 45 into the access chamber, then a 15 drop before a 15 inlet at the drain. Seems pretty chill to me. 

 

The only alternative I can think of is to have had a deeper dig all the way through and a stub stack drop of  1.5m and a slow 90. though the way they have done it seems far easier to access in case of blockages.

Edited July 16, 2021 by Hydra

[Hydra]

30 minutes ago, Temp said:

 

 

Welcome to self building! Someone should have told you that managing people is the hard part. ?

 

Given a choice I would keep the BCO happy rather than the ground workers. You might need the BCO to be more flexible later. So I would try to meet his 60mm per meter maximum if you can. 

 

I'm not even building a house, i'm putting a toilet in a porch, that used to have a toilet in it in the 1970s, which was removed. Now I want it back again! I could have knocked it out in a weekend but instead i've got to create a cavity wall with sheathing and breather membrane built off of the brickwork, with 4x as much insulation as the rest of the damn house. 

 

Can safely conclude, moving a toilet = moving a mountain at least.