Building over a sewer and rodding access

[Pretty Mouth]

Hi all.  Let's begin with rodding access...  

The extension I'm planning to build will be located over a shared sewer, and (amongst many other things) I am concerned about providing enough rodding access to keep building control happy.

 

1930s terrace in a row of 4 houses

Existing extension to rear   3m X full width of house (approx 5m)

Sewer pipe (combined sewer/rainwater) runs parallel to, and approx 3.5m from rear wall of original buildings (according to drain survey).

Manhole access approx 10-15m downstream of the property

 

We want to extend a further 3m into the garden, again full width of the property.  This would leave the sewer running beneath the middle of the extension, without any room for a manhole externally.

 

At the moment there are 3 points connecting to the sewer - a soil stack, a downstairs W.C. and an outside gully.  Currently there's no rodding access to the W.C., there is a small access hatch at the base of the soil stack but I don't know this counts as rodding access.  We plan to move the WC, put a shower where the WC is now, lose the existing gully, and install 2 new gullys outside.  The outside gullys can be roddable, but how can I provide rodding access to the WC and soil stack?  What are my options?

 

Apologies for the low quality diagram.  Red is existing points, green will be new points.

 

[Pretty Mouth]

No replies?  I suspected this may be the case, I've searched high and low for answers , but no luck so far.

My thoughts: 

The main sewer has rodding access via the downstream manhole, and the external gullies will be roddable, so no need for concern there. 

 

The branch from soil stack to sewer may or may not be considered roddable via the access hatch at its base.  My understanding is that the rodding equipment can make its way around the swept bend at the bottom of the stack.  This must have been acceptable at the time the 1st extension was build 30 or 40 years ago, but would building control deem this acceptable now?  Can anyone confirm this  either way?

 

The toilet branch (I not 100% sure if this goes directly into the sewer, or joins the soil stack branch) is probably not considered roddable as the toilet would need removing to gain access.

[patp]

Plumber husband, who worked on the sewage side of Anglian Water for 25 years, searching out many a rodding access, says this -

 

You may have to have a "sealed manhole" within the house. The only other alternative is at the base of the soil stack. He would think that this might be acceptable depending on physical access etc.

[PeterW]

@Pretty Mouth where in the UK are you as different sewage providers have different rules. 

 

For Severn Trent you will need a build over agreement, and I would check your local provider as to what they need you to have first. 

 

In terms of rod access, you can put a sealed access point at the bottom of a stack but it’s a last resort. I would replace everything in the plot boundary possibly with uPVC and use swept entries to the runs - the far right gully I would make into a back access gully and put a long swept bend on it so you can rod or jet from there down the run. The rest, make them as short as possible with minimal turns and always use a 45 degree Y to connect. 

[Pretty Mouth]

Thank you both for your replies and information.

 

patp, I had considered a sealed manhole or inspection chamber, but I suspect it may no longer be permitted.  Thames water (not our regional water company)refuse them according to this guide:
https://www.thameswater.co.uk/-/media/Site-Content/Developer-Services/Guide-to-building-over-or-near-a-public-sewer.ashx?la=en

PeterW, the extension will be in Coventry,  so Severn Trent - we will indeed need a build over agreement.  I will contact ST and ask them for guidance, hopefully they will be happy with the sealed access point at the base of the stack.  I'll report back with any info.

[PeterW]

ST either want you to replace the whole lot in UPVC (it’s probably clay) or pay for a CCTV inspection before and after. 

 

TBH it’s cheaper to rip the lot up and replace it - get the runs ready, don’t forget a couple of slip couplings and basically you can bung the neighbours drain for an hour and replace the lot in one go.