New Waste High Up In Deep Inspection Chamber - Ok?

[EViS]

We will be running a new 110mm drain pipe in a 0.8 metre deep trench to the nearest inspection chamber. The inspection chamber is just over 1.5 metres deep with existing clay pipes entering it.

Can the new drain pipe enter the inspection chamber 1 metre below ground (and 0.5 metres above the bottom of the chamber)? i.e. the waste water will fall 0.5 metres into the bottom of the chamber.

Or does the waste need to run just above the existing chamber 'floor'?

Untitled

• EViS
• 11 Feb 2013
• 1

 

[Hugh Jaleak]

Wont comply with building regs, and also depends what it is carrying. What are you proposing to connect to the new drain?

 

[dann09]

1. I presume that the lower right existing drain is discharging into the IC, and the lower left pipe is the outlet?

2. Is this a clay or a plastic IC? What diameter is the IC, and what size pipes are connected to it?

3. Is there a spare IC inlet on the new incoming pipe side?

4. Typically (for my BCO), 110mm pipe must enter the IC at the same "level" as the bottom (invert) of the IC. What conditions exist for you to propose dropping-in?

5. Perhaps, post pics of the IC base, and maybe a scanned section sketch from the slow bend at the bottom of the S&VP to the IC - give length dimensions.

 

[EViS]

Wont comply with building regs, and also depends what it is carrying. What are you proposing to connect to the new drain?

Right, BCO are involved however I haven't asked them about this specifically.

The new pipe will service a new toilet and shower.

 

[EViS]

1. I presume that the lower right existing drain is discharging into the IC, and the lower left pipe is the outlet?

Both lower pipes are discharging, the outlet runs at the front (not shown on my diagram).

2. Is this a clay or a plastic IC? What diameter is the IC, and what size pipes are connected to it?

Clay IC at circa 600 x 450 opening. 130mm (?) clay pipes.

3. Is there a spare IC inlet on the new incoming pipe side?

No, as this is a brick built IC.

4. Typically (for my BCO), 110mm pipe must enter the IC at the same "level" as the bottom (invert) of the IC. What conditions exist for you to propose dropping-in?

What do you mean by conditions? Otherwise, yes we can drop-in, however it wouldn't be too much more effort or cost just to dig the trench deeper.

Any reason why the new drain pipe can't have a fall greater than 1:40?

 

[limerockconstruction]

I thought I'd read between 18mm and 90mm per metre.

 

[Hugh Jaleak]

A foul connection (especially for a W.C.) must discharge into the chamber into the direction of flow as close to the level of the existing invert as possible. Some further reading here: http://pavingexpert.com/drain05.htm#exmh

Putting a pipe in higher up as you propose could cause a build up of solid matter from the discharge of the W.C., at best it'll create an unholy mess and possibly stink, at worst if this builds up and then falls off in a big lump, it could block the chamber. Also I would think highly unlikely to be approved by the B.C.O.

Greater fall than 1:40, you run the risk of the water leaving the solid matter behind, and again, if the effluent hits the chamber at a rapid rate of knots then there is the risk of splashback and waste spattering over the benching and/or walls of the chamber. If you wish to avoid excess digging then maybe possible to run the new drain at a depth of 0.8m, fitting a backdrop immediately outside the chamber to achieve the 1.5m depth to suit existing invert levels.

 

[dann09]

1. Bit of confusion here: why not post a scanned plan view of S&VP and IC showing the existing incoming pipes and the outgoing discharge to main sewer pipe.

2.Is the IC clay or brick?

3. So it's a matter of falls from the S&VP to the IC? Typically, that issue is resolved by going deeper with the S&VP rest bend.

4. Costs are small for digging out to 600mm -

5. 1:40 falls is the best for solid waste, so that the solid does not part from the liquid and build up a blockage.

6. Is this a shared with neighbours IC?

 

[dann09]

Excuse me, above, i've got the invert depth wrong at 600mm not 1.5m - still a common digging depth.

 

[noseall]

Solid material being left behind regards steeper falls is a myth.

Yes you can have a dropper in a manhole if done correctly, i.e. the dropper needs to be directed so that the flow is aimed directly down stream.

 

[maltaron]

A dropper in the manhole was suggested and approved by my Building Inspector. The incoming pipe has a bend to vertical, down to just above pipe level and a bend to point in direction of flow.