Joining concreted in drainage below foundation level

[Masarius]

Hi all,

I'm currently part way through quite an involved backyard renovation and I've struck a problem (not the first!). There's an old combined storm water / foul water gully beside the house which I'm pretty sure is leaking, but in any case I'd like to replace it and I need to plumb some linear drains in to the same manhole which I was planning to do by making both connections meet an an inspection chamber before continuing on into the manhole using the existing pipe.

The gully is surrounded in a massive chunk of concrete and the pipe goes down quite deep, below the foundation level of the house and it's all concreted in. Due to the high previous ground level (over the DPC) I'm bringing it down as low as I can in a bid to get under the DPC with my new paved area. I was hoping to be able to pipe around the concrete below the foundation level to avoid disturbing it and the foundations but now that I realise it's concreted all the way to the manhole I'm unsure what to do.

At this point I'm thinking of breaking off all the concrete above foundation level, cutting through the mass concrete about 1 metre out from the house and attempting to connect the section from there into the inspection chamber using a PVC to clay adaptor that fits inside the pipe, but I'm not sure if this is sound or not. Any help greatly appreciated!

Untitled

• Masarius
• 1 Jul 2013
• 1

 

[noseall]

Hi all,
attempting to connect the section from there into the inspection chamber using a PVC to clay adaptor that fits inside the pipe, but I'm not sure if this is sound or not. Any help greatly appreciated!

There are no plastic to clay adapters that fit INSIDE the pipe. The connection is made externally and should never interrupt the bore of the pipe.

If it is possible to peck away at the concrete and expose enough pipe to make a connection away from any bends or collars then go for it. We have done it many times but it takes a lot of patience and sometimes there are failures.

Otherwise, if the distance to the chamber is not to great, replace the lot in plastic.

 

[Masarius]

Thanks for the advice noseall, I'll have a go at carefully chipping away at it. What is your opinion on removing the concrete that's directly beside the house? It's about 15cm deep and about 20cm wide for the part that's below the lowest foundation brick and directly adjacent to it. Do you think I could safely remove this (about a 1.2m long section) and replace with my own pipe without disturbing the foundation too much? The soil is heavy clay and its stability seems to vary quite a lot in the different places I've been digging.

 

[noseall]

You are in the lap of the Gods when it comes to nibbling away at pipes surrounded in concrete.

Also there are many salt glaze joint failures or cracks in pipes that run close to, or are connected to the foundation concrete.
This often occurs where an svp and a salt glaze pipe has sheared due to differential movement, but can apply to other nearby pipes.

You are going to have to 'suck it and see' I'm afraid.

 

[Hugh Jaleak]

McAlpine DC-1 will fit inside the pipe, but you still need the remaining pipe to be sound, and keeping that intact when surrounded by concrete is not an easy mission.....

 

[Skimmers]

drop me a msg i can pop over and have a lool

 

[noseall]

McAlpine DC-1 will fit inside the pipe, but you still need the remaining pipe to be sound, and keeping that intact when surrounded by concrete is not an easy mission.....

Surely these things are like a pan connector and are only suitable in certain locations?

How do they cope with flow anomalies and rodding etc?

 

[Hugh Jaleak]

Good point Noseall, whilst I think they may be fine used in a vertical run, I have my doubts as to their practicality in a horizontal run, but if making the best of a bad job I can think of worse ways to 'bodge' a joint!

 

[Masarius]

Thanks everyone for their feedback on this.

The clay joiner did fit inside the pipe and it was the most convenient option for me by far because otherwise I would have had to break out and reseat a new pipe in the manhole which is something I don't have the confidence or experience to mess with. As the connector is right up near the manhole (within about 20cm of it) it shouldn't be a problem for rodding as you'll be able to move past the restriction very close to the opening.

In the end I completely broke out all the concrete and pipe and is now replaced with 100mm PVC also bedded in concrete as it's below the foundation level and that's what the regulations recommend.