Multiple SVPs to single IC....good idea or not?

[Thorfun]

Hi all,

just finalising the penetrations through the basement walls and we originally had 2 x foul pipe penetrations to different inspection chambers outside. But the AT has suggested removing one of the penetrations and running all the SVPs to a single IC. was just wondering if this is a good idea or not? it seems ok to me but as I haven't much of a clue about stuff I thought I'd ask those that do. ?

 

Here's a sketch of what's being proposed.

 

hopefully the sketch is pretty self-explanatory but I'll use words anyway. 

 

soil pipe A comes straight down from an en-suite above and soil pipe B comes down from another en-suite and then goes through the floor and along the ceiling of the basement to join with soil pipe A. Soil pipe C comes from an en-suite and down through to the basement and was originally going out through the basement to the IC coming from the dog shower and shower room above the garage (the squiggly red line denotes that connection being removed) but now it is going along the basement ceiling where it's labelled 4" soil to join up with soil pipe A. the macerator labelled D is from the WC in the basement which will get pumped up to join soil pipe C as shown, it was previously suggested to pump to soil pipe A. So all of those pipes are now being sent out through a single penetration in the basement to the IC coloured in red.

 

can anyone see any issues with this? or should we revert back to soil pipe C having it's own exit from the building?

[Oz07]

Not sure if be happy with that connection, feels a bit unnatural. Would it be accessible to rod from both cupboards or hatches in basement ceiling? I'm sure it would be fine, after all I've got flush invert 90 Dec junction IC and I've never had to lift the lid due to blockage. As long as there was rodding from both ends available, it's pretty close to the IC outside so any problems should be fine. Have you got depth to have the c pipe run 2 or 3 inch higher then a little 15 or 22 bend downwards before it hits the 90 junction? @Nickfromwales is your man to comment. 

[Thorfun]

 

1 hour ago, Oz07 said:

Not sure if be happy with that connection, feels a bit unnatural. Would it be accessible to rod from both cupboards or hatches in basement ceiling? I'm sure it would be fine, after all I've got flush invert 90 Dec junction IC and I've never had to lift the lid due to blockage. As long as there was rodding from both ends available, it's pretty close to the IC outside so any problems should be fine. Have you got depth to have the c pipe run 2 or 3 inch higher then a little 15 or 22 bend downwards before it hits the 90 junction? @Nickfromwales is your man to comment. 

 

this is the detailing of the pipes going through the basement ceiling and out through the wall. maybe this helps to answer the rodding questions.

 

 

the ceilings in the basement are 3m high so we do have a bit of room to play with but the level of penetration through the basement wall is dictated by the invert level of the inspection chambers.  

 

[Oz07]

Interesting stepping up to 150. Looks like you have room to bring that 90 connection into the drain within the top third of pipe which is I believe what building regs ask for. Your ridding points would be on the stack in cupboards above

[Oz07]

What's the detail for sealing pipes like this in basement where they exit the wall and still allowing for movement. Are they solid in the wall with flex bands and rocker pipe outside?

[Thorfun]

7 hours ago, Oz07 said:

What's the detail for sealing pipes like this in basement where they exit the wall and still allowing for movement. Are they solid in the wall with flex bands and rocker pipe outside?

tbh I don't know!

 

 

architects have covered themselves with the NOTE in the drawing but I think the WC foul waste duct will need to be bigger than 150mm if I'm going to slot a 150mm waste pipe through it. I'll need to speak to the groundworkers and basement contractors to see what they say about it all.

[saveasteading]

I prefer the original arrangement.

As there is a horizontal  pipe joining at the bottom of the vertical ( have I got that right?) there would be excessive turbulence when flows collide. Also the vertical is splashing into your big and gently sloping 150 horiz. and could run upstream. Water comes to a stop , solids settle, blockage.

 

Perhaps this could be lessened by a) using large radius connector  at A, or first converting the vertical to horiz, before joining, or the vertical drops further and B to A tumbles into the vertical before bending out.  ie separate the junctions.

there doesn't seem to be space for all this plus rodding points, which would have to be accessible.

I suggest 'revert'.

 

[Thorfun]

37 minutes ago, saveasteading said:

I suggest 'revert'.

thanks. it's definitely an option.

[Thorfun]

so, I think I'm going to revert back to the original plan that was designed by the civil engineers rather than do as the architectural technician has suggested. I understand the reasoning to reduce the number of penetrations through the basement wall but as there are already 7 ducts I don't see the issue with having one more. but I will have to check those penetrations with the structural engineer anyway. and I kind of agree with @Oz07 in that it feels a little unnatural! I can't put my finger on why though.

 

BUT.....just to counter that, back when we were going to have a foul water chamber and pump the civil engineer did design something like that as all the waste was going through one hole in the wall to the foul water chamber. e.g.

 

 

so it is obviously a legitimate thing to do otherwise the civil engineers wouldn't have designed it at one point, right?

 

I'm really confused and not sure which to go with. before I tell the AT on Tuesday to revert I wonder if I could get the expert opinion from @Nickfromwales on this one please?

 

in the immortal words of Princess Leia....."Help me Obi-wan-@Nickfromwales, you're my only hope". ? 

[saveasteading]

It looks simpler on the plan than it is in 3d.   You have the advantage of the building in front of you.

If you have the pipes and fittings on site,  can you hold each in place and see how they would fit, and that the flows are smooth and don't clash?

An additional junction might be all you need to keep it smooth, subject to enough space.

[Thorfun]

26 minutes ago, saveasteading said:

It looks simpler on the plan than it is in 3d.   You have the advantage of the building in front of you.

If you have the pipes and fittings on site,  can you hold each in place and see how they would fit, and that the flows are smooth and don't clash?

An additional junction might be all you need to keep it smooth, subject to enough space.

I can't do this as it's just a partially dug big hole at the moment! basement contractors are coming in a week to start building the basement so I need to get these details sorted before then.

[Thorfun]

to update this thread....

 

I spoke to the civil engineers and they said "we don't normally get involved in things like this as it's internal plumbing"....err....but it's your design! anyway, he then went on to say that he doesn't see an issue with it as long as it's not more than 90° bends. so I take that as being a sign off from civil engineer.

 

I spoke to the groundworker and he said no issues with getting rid of the extra penetration through the wall and the internal run from pipe C to A but you should never run from a larger diameter pipe to a smaller diameter foul pipe like the CE designed after running the 150mm pipe through the wall! you can go from smaller to larger but not the other way around. this kind of makes sense though, right? the waste will be funnelled into the smaller pipe which could cause congestion? like on a motorway when it goes from 3 lanes to 2 lanes due to roadworks? he also said that a 150mm pipe is something you'd find serving 3 houses, not in a single house. which still leaves me confused as to why the CE designed it this way.

 

anyway, as I haven't hired a plumber yet I can't run this by them so I've decided to just go with the groundworker's suggestion and do 110mm waste pipe through the basement wall. 

 

any comments from anyone on this before I send the architectural technician an email in the morning explaining what I want?

 

then I just need to get sign off from the structural engineer that all the penetrations won't affect the structural integrity of the building and I'm good to go!

[Nickfromwales]

The uplift to 150mm makes zero sense to me tbh. 
I second the opinion of not going from 150 > 110mm even though the flow / solids would be at the dead centre and bottom of the pipe at that point. If I was on site there would be no mention of 150mm pipe whatsoever.
110mm can run for a hell of a distance with as little as 1:80 fall, and still accept branches from

2/3/4 even 5 WC’s before ever even thinking of upsizing. 
If upsizing gives any kind of confidence boost, then it won’t cause issue, but it needs to go all the way to the external IC unmolested eg no reduction before it’s final discharge to the sewer chamber. 

Edited May 5, 2021 by Nickfromwales

[Thorfun]

8 hours ago, Nickfromwales said:

The uplift to 150mm makes zero sense to me tbh. 
I second the opinion of not going from 150 > 110mm even though the flow / solids would be at the dead centre and bottom of the pipe at that point. If I was on site there would be no mention of 150mm pipe whatsoever.
110mm can run for a hell of a distance with as little as 1:80 fall, and still accept branches from

2/3/4 even 5 WC’s before ever even thinking of upsizing. 
If upsizing gives any kind of confidence boost, then it won’t cause issue, but it needs to go all the way to the external IC unmolested eg no reduction before it’s final discharge to the sewer chamber. 

Hi Nick, thanks for the response and the confirmation that the 150mm pipe is not required. I will be speaking to the AT today to get the drawings updated and then sent to the SE for confirmation the penetrations aren't an issue structurally.

[saveasteading]

Agreed that the 150 pipe is strange. The only reason for it would be that the flow capacity in the building regs required it for some high capacity that we don't know about. Or it is rather flat gradient (Bad). But a large pipe with a small flow will encourage separation, and blockages. It really needs a review. Check the building regs yourself I suggest, as well as asking your experts.

(btw you can reduce diameter if the slope increases. but that would be in a manhole/chamber, not mid-run. )

 

Document H1, diagram 9.

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

Also see the general principles of avoiding crossflow, as original question.

[Thorfun]

36 minutes ago, saveasteading said:

Agreed that the 150 pipe is strange. The only reason for it would be that the flow capacity in the building regs required it for some high capacity that we don't know about. Or it is rather flat gradient (Bad). But a large pipe with a small flow will encourage separation, and blockages. It really needs a review. Check the building regs yourself I suggest, as well as asking your experts.

(btw you can reduce diameter if the slope increases. but that would be in a manhole/chamber, not mid-run. )

 

Document H1, diagram 9.

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

Also see the general principles of avoiding crossflow, as original question.

thanks. had a quick look at Document H1 and from that quick scan I agree that 150mm is overkill when looking at the tables for flow rates and pipe diameter and gradient.

 

just received confirmation from the SE that the penetrations have no impact on the structural design so I'm happy with it all now. 

[Thorfun]

although, the CE designed that 150mm pipe with a 1:50 gradient so running a 110mm pipe at 1:80 gradient will make the hole in the basement wall in the wrong place! ?‍♂️.

 

but as we have 3m high ceilings I'm not worried if I have to drop the 110mm a little lower and I'm not going back to the civil engineer (who take weeks to respond) to redesign it for a 110mm pipe. I'll just wing it on site and even if I have to use a 1:50 gradient with the 110mm that should still be ok.

[Mr Punter]

Just to add to this:

 

You would normally have an access for rodding / jetting at the base of the stack, in the room above the games room.  Having it on / near the horizontal run is not practical.  In the event of a blockage I would not want to unscrew that!

 

The long radius bend may be able to be moved up a bit into the floor zone to save some ceiling height.

 

I don't know why there is a hydrophilic strip where the pipe goes through the ground floor.

 

I assume the IC is deep as it has to take drainage from elsewhere?  Try to keep them as shallow as possible.

 

 

[Thorfun]

1 hour ago, Mr Punter said:

Just to add to this:

 

You would normally have an access for rodding / jetting at the base of the stack, in the room above the games room.  Having it on / near the horizontal run is not practical.  In the event of a blockage I would not want to unscrew that!

 

The long radius bend may be able to be moved up a bit into the floor zone to save some ceiling height.

 

I don't know why there is a hydrophilic strip where the pipe goes through the ground floor.

 

I assume the IC is deep as it has to take drainage from elsewhere?  Try to keep them as shallow as possible.

 

 

thanks. I believe the IC depth is due to other invert levels and then the final invert level of the STP.

 

I also haven't a clue what the hydrophilic strip is for! I will speak to the plumber but, ultimately, will just ignore that.

 

I understand about the long radius bend moving up to save ceiling height but that will change the penetration height for the foul pipe and that's a can of worms I don't want to open as the basement contractors are starting next week. as it's currently designed we'll lose about 500mm of ceiling height in the games room so it'll only be 2500mm high! I think we can live with that. ?

 

point noted about the rodding point. will bear it in mind when speaking to the plumber about it all. think I've had enough of the civil engineer and the fees they charge.

[Oz07]

The pipe size shouldn't impact penetration heights as you will be working off invert levels anyway ie bottom of pipe. It would only add an extra 40mm on top of the height if upsizing. Like has been said though 110 simpler all around