To pump or not to pump ...

[Ed_]

Demolish and rebuild.

 

The levels to my existing sewer connection are marginal, and due to excavation I will have around 200mm cover over the pipe under a parking area.

 

I think it might be possible to make this work with ductile iron pipe?

 

Or I can make a new connection, that's £5k.

 

Or I can put in a pumping station and that's £1k.

 

Struggling to decide. Pumping station seems most cost effective but is it wise to lock in a pumping station long term?

 

Interesting in everyone's thoughts/experience. Thanks.

[Big Jimbo]

I would do anything other that a pumping station. That would be last resort IMO

[Mr Punter]

I can't see a pumping station costing as little as £1k supply and fit.  Good luck when it fails (which it will).

 

New connection or RC slab over pipe.

[ProDave]

As above, pumping stations are a last resort.  I am sure you can design the parking area with a suitably reinforced construction to not harm the pipe.  Raise the height of the parking area would be a good start to give enough cover to reinforce it.

[Conor]

Just use standard PVC pipe and surround in concrete. There should be a detail in the BC regs for this. What fall do you have with that cover?

 

If it all goes wrong in the future, then you can look at a new connection. Definitely worth the gamble.

[Iceverge]

Pour concrete around it. It'll last for a century. 

 

One caveat, I would be worried about vibrations being transferred directly from the concrete into the pipe or if the slab settled it could crack the pipe. 

 

To avoid this I would excavate and consolidate well under the pipe. Wrap the length under the concrete in some pipe installation. 

 

 

And maybe include some mesh bridging over the top. 

 

 

 

 

 

[saveasteading]

50 minutes ago, Iceverge said:

mesh bridging over the top. 

Agreed that is my choice too IF you have the falls.

It is going to have car loading which is considerable. 

So I'd say you bridge it completely, with concrete downstands (tiny footings) on both sides  and a reinforced slab over it. The mesh shouldn't be plonked in  but laid at mid height. Thus the load doesn't bear on the pipe. 

It may need a smart drawing and explanation to show the bco but the work can be diy.

 

I've only installed pumped mains twice and on a larger scale. It was compulsory to have 2 pumps and the cost was huge.

[Ed_]

I can't raise the parking area unfortunately, right next to the house.

I can probably just make it work with 1/80 fall, but it's very marginal, i'm having to design junctions very precisely and always wary that the consequence of an error anywhere is that it won't work.

 

Does anyone have any experience of using ductile iron pipe? I've found a few things saying it can be buried shallow as strong enough to take the load, haven't found much detail and not sure how BCO will view it.

 

Mesh bridging - do you mean to reinforce the concrete?

[Oz07]

3 hours ago, Conor said:

Just use standard PVC pipe and surround in concrete. There should be a detail in the BC regs for this. What fall do you have with that cover?

 

If it all goes wrong in the future, then you can look at a new connection. Definitely worth the gamble.

Ive done this before and sure i pulled the detail from bregs doc. Movement joint at 3m. It had a bit more cover though maybe 450-600mm

[saveasteading]

2 hours ago, Ed_ said:

Mesh bridging - do you mean to reinforce the concrete?

Yes. reinforced across the pipe, perhaps with a gap to emphasise the absence of loading on the pipe. Or you could use a steel plate instead or as well. That would be nice and thin as well.

 

It isn't in the reg's as such because it is becoming an Engineered solution. The bco may accept it without an Engineer's proposal, if they are confident enough to see that it is obviously a sensible solution.

 

I'm thinking, concrete surround the pipe while you are at it.

[Bonner]

I’ve got less than 200mm cover albeit close to the house. I would be concerned by a concrete mixer, cars exert relatively low ground pressure, and that is distributed significantly even 200mm depth. Also more confident about PVC pipe which will flex, than a rigid pipe.