Build over Thames Water sewer for extension

markwidgery

Hi. I am getting a little freaked out. I have planning permission for a large extension to the side and rear of my semi-detached house. I did the plans myself on sketchup so we've not had an architect involved. There is a sewer running through the back garden with a manhole cover over an inspection chamber. My plans put this manhole cover in my new bedroom.

My builder assured me before building that we could lintel over the sewer and install a double-sealed cover in the bedroom - not perfect but not a real problem. The sewer and manhole covers have been built over in a similar fashion on both sides of us.

We put in a building notice application and the inspector has been round and seemed positive.

So far they have knocked down the conservatory and utility room, and are about to start the footings. I got a letter from Thames Water, my supplier, yesterday. They say I need a build-over agreement for any work over a public sewer. More significantly, they say they will not allow you to build over a manhole cover, even with a double sealed cover.

Having read their stuff, I now understand that all shared sewers became public in October 2011, and are therefore owned by Thames Water now. I got the neighbours to flush their loo and it comes through, so I know it is shared.

Anyway, my builder called building control, who told him to contact Thames Water. They said on the phone we will need to divert the sewer but I have no idea how that might work, since it is built over on both adjoining properties already. Their information says 'where feasible Manholes should be removed and piped through. Manholes should be constructed outside your extension'. If they allow me to cover and pipe-through do they also require a replacement manhole? If so there is nowhere to put it as the extension covers the entire run within my property boundary.

Just in case it is important there is a photo of the inspection chamber. The pipe runs 1.40m beneath the manhole and is about 15cm in diameter.

Interestingly as I searched I came across this document which seems to contradict some of the stuff they sent me

Page 3 final question says:
"If a property owner wishes to build over a sewer or lateral drain after October 2011 and
there are not any public sewers illustrated on the map of sewers in the area under
consideration for development, what would be the property owner’s position with regards
to requirement of building over approval?

A) Property owners are legally required to notify the local building control department of building
work or works to repair, reconstruct or change the course of a drain or sewer. However there is
no current requirement for the building control office to inform customers or Thames Water that a
building over agreement may be required where the sewer in question does not appear on the
map of sewers. It is the responsibility of property owners to make diligent enquiries to determine
whether the drainage in the vicinity of any proposed development will affect property and to seek
the approval of the owner or owners of the sewers, or drains that may be present prior to
construction."

I checked the sewer map we had done when we bought the place in 2007 and this sewer is not shown on there. Obviously Building control will have the up to date one to look at. This statement seems to imply that it is up to building control rather than TW if the sewer is not on the public sewer map.

I am fine to put in the build-over application but I am concerned about the implications. While I can accept some delay and degree of extra expense, I am concerned that they could simply turn round and say no. If we can't do anything about the manhole, it completely scuppers our rear extension.

Has anyone had similar dealings with TW? Are they reasonable in allowing something to be done that would not have been an issue before October 2011? Am I missing anything important here?

It seems odd that a piece of legislation brought in to simplify maintaining sewers could have the effect of making my back garden a no-go area for extending. Any advice would be extremely welcome. Thanks in advance

I tried attaching or linking to the floorplans and photos but since I am a new user it won't let me. Irritating

"Sorry as a new user you are not allowed to post with links. This is done to stop spammers clogging up the site. Please edit your message below to continue."

Hopefully someone has some good ideas??

Doozergirl

The extension runs boundary line to boundary line? Is it a narrow plot?Do your neighbours have manholes? It might be that TW will give the build over agreement with no manhole if the run is able to be rodded from either side. Otherwise you may have to divert the sewer if a decent angle can be found.

Not only will the water company not allow manhole within the house, you will not want one! When the neighbours' waste starts backing up and the blockage is by you and they're jetting in your bedroom?! Eeeew! :eek: it's a matter of when, not if.

Severn Trent are very friendly and act like they are there to help, not hinder. I'm sure Thames will be similar. Call them.

Your builder is a fool. This takes weeks. Building over without permission could, in the worst case, cost you a future house sale. There's always a way around these things though. You are going to need to spend some money at least capping the pipe properly and removing the current manhole - that's the best case scenario.

jimmy_cricket

I wouldn't worry. My neighbour has built over Thames Water's sewage pipe. I posted on here about it as it was left open for over a week. On contacting Thames Water, I was told that no agreement had been sought or granted "But they would write a letter to the householder if I liked".
Still to this day, it has not been inspected and the extension is now built. Oh, and my drain (which is connected to the one built over) has just blocked and backed up, which Thames Water had to come and clear.

fluffymuffy

Doozergirl wrote: »

Severn Trent are very friendly and act like they are there to help, not hinder. I'm sure Thames will be similar. Call them.

Having now done about 6 build over notices to Severn Trent they have been OK when it's straighforward. Straightforward means application form +fee+ before construction CCTV footage and report from sewer inspection company (e.g Dynarod, or Metrorod, or Thingyrod) , and then post-construction CCTV footage + report. Obviously I charge for all this faffing too and so the client sees about £700+ in total added to their job before anything much happens. And that's just building near or over. And they don't always agree to building over. Sometimes they just won't allow it - "for access purposes" - and that wasn't even an inspection chamber - just a pipe.


When it's not straightforward they are still friendly to deal with but incapable of agreeing among themselves what needs to be done and getting an approved solution down in writing.

Doozergirl wrote: »

Your builder is a fool. This takes weeks.

Hope the OP's DIY plans effort extended to producing a full plans submission for Building Control and he's not relying on this daffy builder to construct the extension on a Building Notice.

Doozergirl

jimmy_cricket wrote: »

I wouldn't worry. My neighbour has built over Thames Water's sewage pipe. I posted on here about it as it was left open for over a week. On contacting Thames Water, I was told that no agreement had been sought or granted "But they would write a letter to the householder if I liked".
Still to this day, it has not been inspected and the extension is now built. Oh, and my drain (which is connected to the one built over) has just blocked and backed up, which Thames Water had to come and clear.

They may not have trouble now but your neighbours will have a tremendous headache when they come to sell!

markwidgery

Thanks for all the input. The lack of links and attachments is irritating. If you want to see the images there are some plans and photos on picasa, just search for picasa then my first and last name with a space between in google. Under building regs folder. In answer to Doozergirl the plot is 9.4m wide and we are building over almost the entire width (bar a little on one side for access). There are manholes on either side, both inside their respective extensions but remain accessible.

My big hope is that, as Doozergirl suggests, they will allow me to cap over the pipe and remove the manhole completely. This would leave more than 10m between manholes - anyone know if there is a minimum distance they allow?

Thanks again

Doozergirl

Worst case scenario is that they will ask for a new manhole where your access is at the side. Please do not have a manhole in the house, even if it's an option.

Winter_Phoenix

Doozergirl wrote: »

Please do not have a manhole in the house, even if it's an option.

Doozergirl is absolutely right. I know someone who had a properly-double-sealed cover in their 1970s kitchen extension floor, not mentioned to them when they bought the house. When the inevitable drain blockage happened, raw sewage was forced up around the ageing seals, and a kitchen unit had to be removed to allow the manhole cover to be taken up. It was bad in a kitchen, with a floor which could be disinfected easily, and everything scrubbable or bleachable. In a bedroom, it would be a complete nightmare.

PS: Is your house insurance company OK with your plans? I suspect they won't be too happy if you have to claim for new bedroom carpet, bedding, etc. a couple of years down the line. (Sorry to be so pessimistic! Good luck with whatever you decide to do!)

southcoastrgi

put the links here without the www. then they will just show as text

markwidgery

Thanks. Try pasting this into a browser with https:// before it

picasaweb.google.com/107365430337460511640/BuildingRegs

Doozergirl

Well, if you all have double sealed manholes inside your houses, someone is going to have to open theirs up to rod! Honestly, the plan looks like a terrible option. I'm almost certain that TW will not allow a manhole inside (and that one seems huge), but leaving one out altogether doesn't look like an option either really, you're going to have to rely on others opening up their indoor manholes to rod. No one is goin to be able to jet - which would be preferable.

Obviously, you'll have to ask TW what they think, but my gut says you might have to bring your living room extension in enough to fit a manhole to the side on the outside. A 9 metre extension or 10 isn't going to make to most huge of differences to your quality of life.

I can't make head nor tail of the proposed floorplan - is that what it's going to look like? Creating a better flow could save some money and maximise house value.