Foul Drainage

[Judith Birkett]

Hello

I have an issue that I am unsure how to solve.



I am looking to get a single storey extension added onto my property.



Please see attached floor plans, existing and proposed.



The extension would be over a public sewer (blue), therefore I need a build over agreement. I have decided to have the manhole moved to form a new y junction onto the main public sewer.



I have new fowl water pipes (pink) going to the new inspection chamber from the

1 Existing SVP pipe

2 New Utility (I was told by my architect that I could not simply join it to the existing SVP for some reason, blockage)

3 New WC.



I noticed that a lot of the new pipes are going either under or over the existing public sewer pipe. Is that acceptable or even possible??



Would it be possible to simply join the utility piping to the WC piping and route the fowl water out that way?



Will and inspection chamber actually be able to accommodate that many pipes at that angle?



All seems a bit confusing to me so any help would be greatly appreciated.

 

[Newboy]

I noticed that a lot of the new pipes are going either under or over the existing public sewer pipe. Is that acceptable or even possible??

As long as there is sufficient fall and separation then not an issue.

Would it be possible to simply join the utility piping to the WC piping and route the fowl water out that way?

Not a good idea - a blockage would result in foul water rising in the utility room.

Will and inspection chamber actually be able to accommodate that many pipes at that angle?

An chamber can take the quantity but the entry angle will need to be altered to allow for the waste to follow a natural line into the channel (and be accessible for jetting/rodding should the need arise).

If the 'Y' branch is the connection shown in your new plan then this is subject to the sewer owner accepting a connection in that position. If proposal to rejoin to a new chamber (under the dining table) then no.

Where are the boundaries to your property and are you detached/semi/terrace/end ?

 

[ivixor]

The boundaries appear to be there, marked in red. If so, then you may be out of luck. You have no place to move the manhole to, and the water company will likely not permit you to simply delete the manhole. The manhole you have to collect your own drainage is not a manhole on the line of the shared sewer, so doesn't count.


Below is what we have done. We moved the manhole to the right. Anglian water approved this with no issues.

 

[Judith Birkett]

Thankyou both so much for your input.

1. see attached drawing. I have seen the following drawing done by an architect whereby they connect the kitchen sink and WC sink directly to a public sewer with no inspection chamber over those junctions. Is this ok to do? It sort of makes sense to me, as you would not have as much material that could cause a blockage from these, potentially, or is the architect just wrong and you can't do this?

2. With regard to simply deleting the manhole, I understand what you are saying Ivixor about the new inspection chamber not being on the line of the existing public sewer, however, I looked at some guidance where by the manhole under the extension has been completely removed and a new inspection chamber placed at y angle to it not on the line of the existing public sewer. the idea I think is that you can then rod the junction from the new inspection chamber to clear a blockage. does this not sound correct? (see link to guidance page 7 )


https://www.thameswater.co.uk/-/med...ilding-over-or-near-a-public-sewer.ashx?la=en

Many Thanks

 

[ivixor]

The only one who can say for sure is the drainage authority. However, they only care about their own sewer. Building Control is the next hurdle - as has been mentioned, they are unlikely to approve a plan where the flow needs to effectively double back on itself.

 

[Hugh Jaleak]

All sections of a foul sewer should be accessible for rodding/jetting should the need arise. Blind connections into an existing run, especially under a building, are very unlikely to be permitted. Kitchen drains, can and do block, I've had to clear one blocked on the outlet from the gulley this last week. Fat and soap buildup was sufficient to block a 4" pipe completely. WC's are often abused, no way could you have a WC connected to the drain on a blind run, it must be accessible for maintenance.

Judith, I cant make out your drawing on your initial post, the drainage runs are just too small and faint. Any chance of marking them more clearly and reposting so we can see what the proposed runs are please? There are options if drains need to run back on themselves, a Marscar bowl is one, but will need to see the layout to determine exactly what may be feasible.

 

[ivixor]

What I would do here is get rid of the utility room/wc, and leave that area unbuilt with the manhole on the main sewer there. Then put your utility room and WC where the back half of the garage is. If you want to keep a fullsize garage you will need to extend it forwards and figure out what to do with the front door.