Advice on outside drainage

RoughNeck

Kiran said:

I assume your new pipe is the one coming in at 90 degrees. If so, that benching is not great, also is the incoming pipe rising slightly? Have you got a depth on the invert level of the main run? Also, what is the distance between the manholes?

Distance between waste pipe to shallow drain is approx 9 metres, and then another 9 metres to the public sewer. Isn't there supposed to be a certain level of fall per length? I did see it the other day, but I can't remember what it was.

stuart45

You need to measure the length of the run. 1 in 80 is about right for a 4 inch pipe. You can go a bit more to 1 in 110, but that's about it. 

FreeBear

There should be a chamber installed where ever there is a change in direction of a pipe - Your waste appears to do a 90° turn just past the gate. No rodding point where the waste comes out of the wall either. Not good if you get a blockage. Was this work signed off by Building Control ?

Section62

RoughNeck said:

Ok. So I've taken some more photos and also a carpenter friend of mine came over to help and suggest/measure things.

Hideous pipe covered in concrete - this is the waste pipe that comes from the cloakroom. You can see it just about goes under ground where our blue gate is. This then eventually joins the main waste pipe (from upstairs bathroom) on the corner, and runs into our shallow drain.

Shallow drain: Putting my editing skills to the test (!) I've put the direction of flow, noted the kitchen sink waste and the direction to the public sewer. The depth of the shallow drain is about 230mm, touching the bottom of the lowest pipe.

Public sewer: I was surprised, but the depth of this is about 800mm nearly touching the bottom of the main waste pipe, so that does give us some wiggle room.

My friend thinks that we should be able to lower our shallow drain by someway, all the way to the public sewer, without having to make any changes to the public sewer. I just need to find out what the regulations are with the public sewer and whether there needs to be a certain level of fall into it. I hope this helps!

The depth of the chamber alone isn't enough information - the depth is partly related to ground level and by the looks of it the level of the grass where the public sewer is located is significantly higher than the ground level at the front of the house.  What you need to do is have someone with a level (doesn't need to be laser) to measure the "invert levels" in the public sewer chamber, the chamber in the patio, and the level of the underside of the soil pipe where it comes out of the wall.  You then need to calculate the level difference which with the length of the pipe will give you the "fall".  Ideally you'd be aiming for a fall of (say) 1 in 40 along the whole length of the pipe - it could be a bit flatter than that if necessary.  I suspect the actual fall is minimal, hence the builder doing a bit of a bodge by bringing the pipe up above existing ground level.

You can't make any changes to the public sewer chamber without permission from the water (sewerage) company.  However, if you are really stuck with achieving enough fall to achieve self-cleansing velocity (i.e. your drain is really flat) then it might be worth exploring with the water company whether the public sewer can be relaid to give you a bit more depth to work with.  This is unlikely to be cheap though.

Kiran

RoughNeck said:

Kiran said:

I assume your new pipe is the one coming in at 90 degrees. If so, that benching is not great, also is the incoming pipe rising slightly? Have you got a depth on the invert level of the main run? Also, what is the distance between the manholes?

Distance between waste pipe to shallow drain is approx 9 metres, and then another 9 metres to the public sewer. Isn't there supposed to be a certain level of fall per length? I did see it the other day, but I can't remember what it was.

1 in 60 is better with water saving appliances, but 1 in 80 will be ok. You want the pipes to be self cleansing.

From your second photo that pipework does look rough, even if the height of the waste pipe exit is dictated by what is going on inside, the pipe should have come out of the wall and turn straight down, that way your pipe would be below ground. Also, the grey strap on boss that has been used to take the sink waste is meant for above ground drainage, not burying in concrete or below ground.

It needs an inspection chamber when changing angle of 90 degrees and I'm guessing there is no stack attached to the pipe, at best there may be an air admittance valve but if not it needs some kind of vent. 

fluffymuffy

Ask your builder for a Building Regulations Completion Certificate 

stuart45

Guess work on those measurements, you'd be struggling to get the correct fall on the pipe considering the amount you need to drop it down to get it below ground level.

RoughNeck

fluffymuffy said:

Ask your builder for a Building Regulations Completion Certificate 

He wasn't cut out for the job. Whilst he did complete it, his workmanship was questionable and costs started to spiral, so we went with the easiest options just to get rid of him. A building regulation certificate would be nowhere to be seen I'm sure, if I asked.

RoughNeck

Kiran said:

RoughNeck said:

Kiran said:

I assume your new pipe is the one coming in at 90 degrees. If so, that benching is not great, also is the incoming pipe rising slightly? Have you got a depth on the invert level of the main run? Also, what is the distance between the manholes?

Distance between waste pipe to shallow drain is approx 9 metres, and then another 9 metres to the public sewer. Isn't there supposed to be a certain level of fall per length? I did see it the other day, but I can't remember what it was.

1 in 60 is better with water saving appliances, but 1 in 80 will be ok. You want the pipes to be self cleansing.

From your second photo that pipework does look rough, even if the height of the waste pipe exit is dictated by what is going on inside, the pipe should have come out of the wall and turn straight down, that way your pipe would be below ground. Also, the grey strap on boss that has been used to take the sink waste is meant for above ground drainage, not burying in concrete or below ground.

It needs an inspection chamber when changing angle of 90 degrees and I'm guessing there is no stack attached to the pipe, at best there may be an air admittance valve but if not it needs some kind of vent. 

I agree. Even if it went straight down, at least only a part of it is visible. I guess the issue was always the fall. I also like your inspection chamber comment. It would be great to have one of these on the corner where the cloakroom waste pipe joins the upstairs bathroom waste pipe and would help us be able to sort out any blockages.

RoughNeck

I have now e-mailed the 'Sewer Support Team' helpdesk with my query. Let's see what they come back with. I'd likely need someone with a laser to take an accurate measurement to work out the required fall and whether it's feasible. Even dropping it slightly would help with carrying the waste away at least. But it would be nice to drop it enough to get rid of the eye sore.

Thanks again for everyone's advice.