Drains Under Extension - limited room for Inspection Chambers / Rodding

[BobSlayer]

Hello

We are about to extend our kitchen. Single story extension.
I am scratching my head to make a pan for the drains. We have limited room for external inspection chambers and rodding points as our property and new extension will sit on the boundary on 3 sides.

- The new kitchen will be the area in blue on the plan, up to the boundary wall
- Green dotted kitchen = existing kitchen. This area has a bathroom above which will be retained. With the walls opened up on the first floor with steel beams.
- Red hashed = current single story utility room which will be demolished.

- Yellow dotted line = existing drains that run through our garden into a main sewer. We do not share drains with any other property.
- purple dotted line = proposed new drain from new bathroom, connecting to existing yellow drains. *

- The extension will build over an existing inspection chamber (red rectangle with x). Which we will do away with.
- The black rectangle is where we propose to put in a new inspection chamber outside
- It seems we may need a rodding point in the new bathroom?
- The current position of the stack is marked with two circles, would there be any problem if we wanted to move this?

Can anyone see any major issues here or additional points I should consider?

(* Should I consider replacing all the drain under the extension with new drains? For piece of mind? I could then also potentially move the drain nearer the outside wall in the extended kitchen so it can pick up new services?)

Other info
- house is 200 years old
- the new bathroom / bedroom is a 70's garage. Which we are converting into accommodation
- existing green kitchen is also 70's built

If the image doesn't show above here is the link
https://drive.google.com/file/d/1Mn7k7j1z6T65Azsd2_uie4OMSSCZDDbn/view?usp=sharing

 

[johnny2007]

Surely you will need to re-route the existing stack otherwise it will be in the middle of your open plan kitchen.
Haven't done drains for a living, but I have seen stacks passing through bedrooms (encased and sound insulated) with an accessible rodding point behind.
Usually a cutout in the casing held by 4 screws.
Needless to say, I've never seen such rodding points being used, but I am sure our friendly drain specialists have seen it all.

 

[^woody^]

Form internal chambers with sealed covers

 

[BobSlayer]

Surely you will need to re-route the existing stack otherwise it will be in the middle of your open plan kitchen.

Cheers, yes, there will be a utility room at the back of the Kitchen, between the kitchen and the new bedroom (converted from the garage) - I didn't show it here as it seemed to complicate the drawing. So the current plan is for it to go up and internal wall.

My main concern is having enough inspection / access for the drains if we are building over most of it?

 

[BobSlayer]

Form internal chambers with sealed covers

Obviously this is an option - It could be possible to put an internal inspection chamber in the above mentioned utility room back of the kitchen?
- do you think it is necessary?
It seems that building inspectors / water companies are not keen on them as an option?

 

[^woody^]

If these are your drains then the water company has no say in any chamber's location. If they are not your drains then the water company is unlikely to permit any internal chambers. Building control have to accept internal chambers if constructed properly and sealed.

Your plans are confusing and you are better off showing an existing and proposed, or just using a different shade for new walls, but keep all external walls the same thickness and likewise internal walls.

And were are the doorways? Presumably that new bathroom is an en-suite, in which case it might better off at the back of the kitchen as you may not be permitted to bend the drain run like that without access points at the changes in direction.

 

[BobSlayer]

If these are your drains then the water company has no say in any chamber's location. Building control have to accept internal chambers if constructed properly and sealed.

Ahhhhhh super big thank you Woody - there is a pint waiting for you in Worcester!

Your plans are confusing

Sorry yes I knocked them up on an online programme with my limited skills! I can see I missed a few doorways. Cheers for the tips.

that new bathroom... might better off at the back of the kitchen

We tried it here and it didn't work as well. Being at the front means it has the flexibility to be an ensuite for this bedroom and a downstairs WC / shower for the rest of the house.

Anyhoo. Big big thank you
So I think an internal inspection chamber at the back of the kitchen (in the utility) where the run bends will solve all our potential problems. I had been operating on the erroneous assumption that this was not possible.
- And I think we need a rodding eye somewhere in the bathroom?

 

[^woody^]

This should work with no internal chamber. The branch will be just after the rest bend, and everything is roddable from the stacks.

Air admittance valve on the stub stack

 

[BobSlayer]

Ah... very interesting
Is there any reason you have removed the shower and moved the WC?
- was there a problem with this set up as we really want a shower and WC here.

 

[^woody^]

Because it then allows a straight drain run to the other connection point. Any bends are potential trouble spots, so inspectors may want more access to deal with any blockages that may occur.

It's no good planning a bathroom layout that can't be done if the drain layout wont allow it.

 

[^woody^]

You could potentially have the toilet in the other corner and then connect to the stub stack where I have put it by a pipe along the wall, but that will mean the stub stack is in the shower area, so will need to be designed around.

 

[BobSlayer]

Hmmm OK I see - what would I need to do in order to retain the shower and sink as well as the WC?
- Straight line directly line from the WC in the original position
- with branches joining from the sink and the shower?

 

[BobSlayer]

Our posts crossed

You could potentially have the toilet in the other corner and then connect to the stub stack where I have put it by a pipe along the wall, but that will mean the stub stack is in the shower area, so will need to be designed around.

We could probably make that work

 

[BobSlayer]

Super big thank you... still some head scratching to be done, but i feel we are getting there and I should at least be able to work out where I am digging x