Sewer drainage under garden advice

bery_451

Hi,

Were building a new bathroom upstairs at the side of the house and the new toilet there has to drain into the existing sewage mains pipe under our garden.

Our old bathroom downstairs at the back drains into sewage mains pipe underneath our back garden.

I believe we dont have a manhole. Is it best to have one?

Instead of digging up the whole back garden and possibly front garden to find this pipe is there a way to obtain information or a map that shows where the sewage pipe is?

minicooper272

Short answer is, yes you can trace the sewer without digging the whole garden - there are a few options - easiest is to use a SOND, which is a tracker on a rope that the pass through the pipe. It really needs a manhole up or downstream for them to access though.

you can also get a survey carried out with ground penetrating radar, which detects voids in the soil. It's not cheap and not always successful though!

You don't need to excavate the whole garden though - your pipe will be quite shallow (half a metre deep) and a couple of long but narrow trial trenches would track it down if you have a rough idea where it is.

Does the pipe serve your house only, or neighbouring properties as well? (Edit: I'm asking because your water company sometimes has maps showing roughly where the pipe is, but not usually if it only serves your house)

bery_451

minicooper272 wrote: »

Short answer is, yes you can trace the sewer without digging the whole garden - there are a few options - easiest is to use a SOND, which is a tracker on a rope that the pass through the pipe. It really needs a manhole up or downstream for them to access though.

you can also get a survey carried out with ground penetrating radar, which detects voids in the soil. It's not cheap and not always successful though!

You don't need to excavate the whole garden though - your pipe will be quite shallow (half a metre deep) and a couple of long but narrow trial trenches would track it down if you have a rough idea where it is.

Does the pipe serve your house only, or neighbouring properties as well? (Edit: I'm asking because your water company sometimes has maps showing roughly where the pipe is, but not usually if it only serves your house)

Its a semi detached house as there be neighbours. I live in Birmingham. Who is my water company and how do I get maps off them?

SOND requires a manhole?

tealady

bery_451 wrote: »

Its a semi detached house as there be neighbours. I live in Birmingham. Who is my water company and how do I get maps off them?

SOND requires a manhole?

If you live in Birmingham it will be Severn Trent usually. Parts of Sutton come under South Staffs

Davesnave

bery_451 wrote: »

I believe we dont have a manhole. Is it best to have one?

Instead of digging up the whole back garden and possibly front garden to find this pipe is there a way to obtain information or a map that shows where the sewage pipe is?

It won't be optional. You'll need at least one inspection chamber to meet building regulations and the work will need to be signed-off by building control.

It is very likely that there will be a drainage map avalable from your your water company. Digging blindly is not a good idea, as even a small digger can dislodge a pipe before anyone realises it's there.

You might be able to intercept your existing pipe in the back garden without making a direct connection to the shared main sewer, but much will depend on the specific situation.

minicooper272

Davesnave wrote: »

It won't be optional. You'll need at least one inspection chamber to meet building regulations and the work will need to be signed-off by building control.

It is very likely that there will be a drainage map avalable from your your water company. Digging blindly is not a good idea, as even a small digger can dislodge a pipe before anyone realises it's there.

You might be able to intercept your existing pipe in the back garden without making a direct connection to the shared main sewer, but much will depend on the specific situation.

Drainage maps from water companies can be pretty poor - I've found pipes a good few metres from where the map showed before, and they don't normally hold anything for a private dwelling...

You can dig by hand to find the pipe, but far better to have a reasonable idea where it is first by tracing it.

minicooper272

bery_451 wrote: »

Its a semi detached house as there be neighbours. I live in Birmingham. Who is my water company and how do I get maps off them?

SOND requires a manhole?

For semi-detached houses, you might find you have a shared sewer running through both gardens that then connects you to the mains sewer. Neighbours might have a manhole in their garden, so it's worth asking them.

Contact your water company's customer services team, they'll have access to a mapping system and can provide plans (you might have to pay £20-30 for it though). I would ask them if it shows anything within your boundary (or just outside it) if they can tell you over the phone before you pay. Like I say, it can often be very poor though.

The SOND needs a manhole because they need somewhere to drop it in and take it out again. You could have a manhole somewhere that a previous owner buried, but hard to know where. If your neighbours have one, check in a similar place in your garden.

Davesnave

minicooper272 wrote: »

Drainage maps from water companies can be pretty poor - I've found pipes a good few metres from where the map showed before, and they don't normally hold anything for a private dwelling...

You can dig by hand to find the pipe, but far better to have a reasonable idea where it is first by tracing it.

I found they had a good idea of where the sewers were at my last 1930's semi, and those could also be extrapolated from manholes, but I agree they'll probably have nothing on the smaller shared/individual foul water drains.

And yes, even quite important pipes, like the supply for a whole village which runs through my property, can be waaay out on their plans. Quite important when building/putting in fence posts with a pile driver!

Some people will scoff, but I got better results from divining that with a couple of bent rods...something I'd try anywhere first, as it's very low cost.

Doozergirl

Have you kept your searches from when you purchased the house? There is a water search in there that contains those water company maps. The CON29DW, if I recall.

Better than spending money on more.

Warwick_Hunt

tealady wrote: »

If you live in Birmingham it will be Severn Trent usually. Parts of Sutton come under South Staffs

It'll still be Seven Trent for waste.

minicooper272

Davesnave wrote: »

I found they had a good idea of where the sewers were at my last 1930's semi, and those could also be extrapolated from manholes, but I agree they'll probably have nothing on the smaller shared/individual foul water drains.

And yes, even quite important pipes, like the supply for a whole village which runs through my property, can be waaay out on their plans. Quite important when building/putting in fence posts with a pile driver!

Some people will scoff, but I got better results from divining that with a couple of bent rods...something I'd try anywhere first, as it's very low cost.

My mum actually was pretty good with divining for culverts, it's worth a shot