Advice on new manhole

[jamesarm]

Hi Chaps,

I am removing an existing Soil pipe and puting in a new run.
This new run will service an additional bathroom.

Ideally I want to fill in the existing manhole/inspection chamber and excavate a new one further along the soil pipe run nearer to the septic tank.

I can get the falls sorted, but was hoping for any advice on the method and materials I should use to construct this new connection and the manhole please.

I am thinking that I dig a hole and cut the existing pipe where I want to join to it, brick up the sides of the pit, and concrete in a manhole cover/frame on top.
But what should I use for the connection between old and new. Currently I have what looks like a half round, y shaped clayware bottom in the manhole pit.

Any advice?

Cheers,
James.

 

[Blagard]

New manhole, altered drainage? - You need approval of your building control authority.

That aside, If your manhole has a junction in it, then it may be serving more than just your old soil stack. You need to know exactly what both branches are doing (tops of the Y).

As for connecting to old clay drains there are adapters for doing just this. They are often sold within the range of plastic underground drainage systems. These plastic systems also have some simple plastic manholes.

Your old drain system could be a modern clay drain with plastic collars or it may be an older type where the connection is a clay collar as part of one end of the pipe. By drilling out the mortar in the collar you can remove the spigot of the pipe going into it and simply fit the drain adapter into the collar. Or, clean cut to the pipe and use one of the rubber type adapters you can get.

Best to go down stream in the pipe a short way to convert from clay to plastic and then use all new plastic to the mahole and beyond.

Use the correct type of bed and backfill to the pipes.
If the drain is anywhere in a traffic area like your drive, get someone else to do it! - Manholes and their lids are built to suit the appropriate use i.e. a pedestrian grade lid will break or bend under a car wheel.

 

[jamesarm]

Cheers Blagard

I am building an extension and have plans in with building control at the mo, these arn't that detailed so I am waiting for there feedback.


The manhole 'Y' is only serving the one soil pipe, the other junction is capped off after previous remodelling of the house.

I like your advice on going downstream a bit - I was thinking a Hep sleeve to 100mm osma, then run the 100mm to the new manhole?

The area will be trafficked, and so looking at the literature, was thinking of a hepworth PPC inspection chamber with 150mm haunching, heavy duty Iron cover and lid rather than trad. brick manhole.

Would this be acceptabe?

 

[Blagard]

The area will be trafficked, and so looking at the literature, was thinking of a hepworth PPC inspection chamber with 150mm haunching, heavy duty Iron cover and lid rather than trad. brick manhole.

Would this be acceptabe?

Hi,

I can't say what is acceptable or not, but hope to point you in the right direction to avoid doing something wrong.

When you put drainage in a driveway you simply need to think about what is the heaviest thing that will drive over it. e.g. If you owned a lorry then you would want it to take those sort of loads.

The pipe runs in a drive also need to be laid to take the loads. For instance, with a drain about a metre down you first put in the bed and surround as specified by the manufacturer and then backfill with a suitable material such as hardcore. Sometimes you may be able to select some fill from your excavated material but may have a higher risk of settlement later.

If your drain gets shallow, say less than 500mm down, then you may need to bed and surround the pipe in concrete, with hardcore backfill.

Manhole size is mainly about getting access and the size of the pipes. In your case you are dealing with the small drainage so your real consideration is getting access to rod them. In a driveway my preferrence would be a small brick built manhole to suit the choice of rectangular cover and frame to be used. You dig the pit, lay a concrete base and then build up from there. Laying in your drainage and channels onto the base before doing the brickwork will make the connections easy. Then just bench it and set the cover and frame to finshed levels. Note, if your drive is block paved, there are covers and frames that take the block paving to give a very tidy finsh all in paviours.

Using a round manhole with iron cover and frame would be fine if they can take the loads, but I am not up to speed on the specifications for them.

You will probably find most of the information about construction/installation on the web site of your drainage goods manufacturer.

 

[Hugh Jaleak]

You need to ascertain what the existing pipes are made from. The newer type of clayware are 'thin wall' sold as 'Hepsleeve' or 'Densleeve' depending on manufacturer. The older type are salt glazed, and have a bigger external diameter. You will need an adaptor to suit the outside diameter of the existing pipe.

Plastic chambers are ok in traffic loading areas, but will require surrounding in concrete for strength and protection. Alternatively, a plastic base can be used, suitably bedded in concrete, then concrete sections used to construct the chamber. Choose a suitable cover and frame to take the weight of whatever will be passing over. Brick manholes are rarely used now, being labour intensive in construction.