Doing away with a manhole

[ashdene]

Hope you guys can help me, I currently have an old manhole in my garden which only really acts as an inspection hatch and only has 1 inlet and 1 outlet on to the next manhole, I have been told I can remove it as it will be in the way of a new internal wall foundation. So my plan is to break it all out and replace the gulley in the manhole with a new length of plastic pipe that will run right through to the next manhole.
However Im a little concerned about how to connect to the existing clay pipe without causing a step or a ridge where poo could build up and cause a blockage

Can I cut a piece of plastic sewage pipe longways in half, place it over the existing gulley section to form a full pipe, seal it all up and then back fill it with Concrete??
Many Thanks

 

[Agile]

If I was a Building Inspector I would not be happy with a foundation formed on top of a drain and old chamber!

Furthermore have you remembered that it may just be an "inspection chamber" to you but to me its a rodding point!

 

[manchestergas]

Concreting in drains

 

[ashdene]

I will be fully removing the old chamber and bridging the pipe with a lintel before building on it, the next manhole is just 3 meters away so should't be an issue

 

[Hugh Jaleak]

Assuming this manhole is on a straight section and wasn't built on a change in direction on the drain then you should be ok. You really need to break the lot out and replace with a section of pipe, bodge jobs on drains can often come back to haunt you. Use a couple of 'Flexseal' couplings and a length of plastic pipe. Pipe will need adequate protection where it passes through the foundation.

Ensure both ends (especially downstream) of the clayware are chamfered to remove any sharp edges where material could catch, and ensure there is adequate access for rodding from either side of this point. Once its buried it wont be easy to get to!

 

[ashdene]

Assuming this manhole is on a straight section and wasn't built on a change in direction on the drain then you should be ok. You really need to break the lot out and replace with a section of pipe, bodge jobs on drains can often come back to haunt you. Use a couple of 'Flexseal' couplings and a length of plastic pipe. Pipe will need adequate protection where it passes through the foundation.

Ensure both ends (especially downstream) of the clayware are chamfered to remove any sharp edges where material could catch, and ensure there is adequate access for rodding from either side of this point. Once its buried it wont be easy to get to!

Thanks very much, it is a straight run so rodding will not be a problem from the next manhole along and the foundations will come upto the base of the new pipe less 50mm then a concrete lintel will bridge over the new pipe, sorry if I was unclear i did not mean I was going to encase the whole thing in concrete and build a wall ontop of it, I just thought that the connectors would cause more problems than the current smooth gulley.

 

[doitall]

And don't forget it needs building control and inspection.

 

[Agile]

All very well using flex connectors and plastic pipe!

But that will give a discontinuity in size.

I would be looking to use similar size s.g. clap pipe and the current pusgh fit connectors!

If the nearest manhole is only 3m away then why was it needed there in the beginning?

 

[Hugh Jaleak]

I completely agree Tony, but the use of the 'Flexseal' type couplings seems to be the accepted practice today. The 'pushfit' plastic couplings are only suitable for the thin walled clayware pipes, if salt glazed pipework is present it has a larger external diameter and the vitrified clay collars wont fit.

Suitable rigid couplings are available to connect salt glazed to both thin wall vitrified clay and uPVC pipes, but these seem to be harder to obtain as most stockists seem to prefer to carry the flexible couplings instead. With the use of the rigid couplings and careful preparation of the ends of the pipes to be joined, a pretty seamless joint should be achievable.

 

[ashdene]

Thanks guys at least I have some options now for connectors, I will dig up the drains and see what size the pipes are and then decide which connectors are best for a smooth internal finish.

Regards Dave

 

[ashdene]

Well ive been busy over the last few days and now ive encountered a problem, the person who layed the original drains has encased all the pipe work in thick concrete so there is no way of finding a clean end to join onto

I have a minidigger with a pecker attatchment coming next week to prepare the groundwork so he is going to have to chop out all the concrete and smash up the old pipework to get it out.

So assuming he does not destroy the manhole I plan to keep, can I run a new plastic pipe into the manhole and render it in to seal it up?

Also the point where the drain enters the downstairs bathroom is also encased in concrete so im ****ed that end too, Im going to have to break through the wall into the bathroom floor void from outside the bungalow to find the plastic soil pipe that I know has been fitted into the old clay pipe inside

Anybody have any better solutions? Please share!!
Thanks

 

[Hugh Jaleak]

Are you replacing all the pipework upstream of the manhole you are keeping? If so then you may as well remove all redundant pipework from upstream of the manhole you are keeping. Machine can work as close as he dares, last section may have to be removed by hand to avoid major damage to the chamber you intend to keep.

Carefully remove the last section into the manhole, and you should be ok to fit a new piece of plastic into the hole left behind, seal it with concrete and make good benching with appropriate mortar mix. You need to get the joint between old and new as seamless as possible to avoid any edges where material can catch.

May prove easier to lay a new run to the downstairs bathroom, and bring it up externally to connect, the old section in the floor can be sealed off and abandoned instead of smashing the place up to find it.

 

[ashdene]

Are you replacing all the pipework upstream of the manhole you are keeping? If so then you may as well remove all redundant pipework from upstream of the manhole you are keeping. Machine can work as close as he dares, last section may have to be removed by hand to avoid major damage to the chamber you intend to keep.

Carefully remove the last section into the manhole, and you should be ok to fit a new piece of plastic into the hole left behind, seal it with concrete and make good benching with appropriate mortar mix. You need to get the joint between old and new as seamless as possible to avoid any edges where material can catch.

May prove easier to lay a new run to the downstairs bathroom, and bring it up externally to connect, the old section in the floor can be sealed off and abandoned instead of smashing the place up to find it.

Running a new pipe to the bathroom is not going to be feasable as I still need to connect to the existing toilet outlet as the bathroom has all been tiled new floor, nice vanity units etc.. All done by previous owner so I dont really want to pull all that lot out to get to the pipework from inside,m i have broken away a top section of the pipe work where it enters the bathroom from outside and luckily I can see the new plastic pipe connected into the clay pipe so it should be fairly easy to chop away a small portion of wall from outside and connect a new plastic pipe.

The new plastic soil pipe will come out the wall 1 meter and then turn 90 degrees and head 5 meters to the manhole im keeping. Do I have to put an inspection chamber at the 90 degree turn point, i dont really want to as it will be inside my new extension and the building ctrl will insist I maintain access to it. (Imagine a lovely new floor finish with a drain cover in it)

Im still waiting for my building regs so cannot currently ask the BCO.

 

[Hugh Jaleak]

Manhole needed at every change of direction in the drain (officially), but even so, i'd be very reluctant to put a bend on a foul drain especially under a building. Whilst a jetting hose should get round if any block was further upstream, a bend can easily be a pinch point where material could catch and cause a problem.

Is there any possibility of getting a straight run from the existing plastic where you intend to connect to outside the building or existing manhole? Otherwise i'd say BCO may insist on a chamber inside, albeit with a sealed cover. Depending on floor covering the internal covers can be fairly unobtrusive though.

 

[ashdene]

its not possible to run a straight pipe from the bathroom without making 3 more changes in direction and needing to install another 15 meters of pipe, I just do not have enough drop on the manholes to get that much run and still maintain a drop