Mini inspection chamber extension.

According to Building Regs H1 Table-11 2015 approved doc, our 800mm deep mini Inspection Chamber (with a +-32cm internal diameter) should not be deeper than 600mm. I believe this is to ensure effective rodding from above.

Q: Could I bring this into compliance by removing the top 200mm riser section and concreting a 450mm IC barrel around it with a 450mm cover at original ground level? Rough sketch attached.

This would make the mini IC 600mm (invert to cover) but the "ground level" immediately surrounding it would only be a +-12cm wide ledge. Don't know if this would comply with regs.

Thanks,

ian

Maybe you need to consider who fitted it and how long ago.

It is only a small amount outside the specifications and not something that I would expect would upset anyone.

The regulations are written to be complied with but there are no drainage police going round with flashing blue lights about to arrest you.

The only exception is a common infringement in bathrooms. On a Thames Water training course we were told that if we ever saw that infringement then we should report it to a hotline immediately.

Hi Agile, thanks for your response.

I had it installed in May 2011 by a recommended specialist. Later that year it transferred to the Water Company together with the shared lateral drain.

If ever we do call Severn Trent for a blockage, it would be bad if they could not rod due to the excess depth.

Regards, ian

Severn trent would find a workable solution, they'll have inherited far worse setups when everything was adopted.

Borehole said:

If ever we do call Severn Trent for a blockage, it would be bad if they could not rod due to the excess depth.

Click to expand...

Jetting is the way to go, I've jetted drainlines that were 12 metres deep.

Andy

Thanks Andy and Thomp, I get the drift. Will probably leave it as is. Cheers, ian

I don't see it being an issue, it's common practice on Developments now to use 4 and 6" Preformed Chamber bases at deep Invert levels, then build the Chamber up using 1200mm Diameter Concrete rings.

Thanks Hugh,

I'm grateful for the invaluable experience and knowledge all you guys have so kindly shared.

Severn Trent will be inspecting soon due to my complaint about the neighbour connecting a WC into the shared open bottle gully on our boundary, believe it or not, just outside our kitchen window.

If they do challenge the inspection chamber depth, I should be able to lower and extend it as previously planned.

Cheers, ian

Borehole said:

Severn Trent will be inspecting soon due to my complaint about the neighbour connecting a WC into the shared open bottle gully on our boundary, believe it or not, just outside our kitchen window.

Click to expand...

Never mind Severn Trent I'd be getting Building Control and Environmental Health from the Council onto that. Gully would normally do one property, so I'd expect that section to be classed as Private, ST wouldn't get involved until it joins the main run.

Strictly against the rules, the mind boggles.....

Thanks Hugh,

Building control can't help, email below.

Severn Trent have confirmed ownership of the bottle gully but it's a tricky one. You are right, probably going nowhere.

Environment Protection team sent a Nuisance Control officer who says he might be able to raise a nuisance claim if/when it stinks and he can see turds etc. Maybe I should pray for a few floaters.

Owner is a single guy still renovating. Very light use of the 2nd WC. Hope he doesn't sell to some poor innocent family.

Plan B is to cover the gully and reroute our "grey water" to our own private stack, leaving the neighbour to deal with any blockages.

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Email from building control: (officer name and contact details redacted)

Dear Mr *******,

Thank you for your email dated 04.12.25.

A visit was made to your property on 1st September 2025, which confirmed that the neighbouring/adjoining property has wastewater discharging into an open hopper.

The following information applies in this instance; these post-war houses were originally constructed in this manner. The internal soil and vent pipe (SVP), typically made of cast iron, that could not be adapted (“bossed”) into to accept additional connections as modern materials allow.

Consequently, wastewater from the wash hand basin (WHB) was designed to discharge into an external open shared hopper, usually via a lead pipe.

Please note:

There were no building regulations in place at the time these properties were built. The Building Act 1984 introduced building regulations from that year onward.

Building Control has no jurisdiction over homeowners who remodel bathrooms, and there is no requirement for a Building Regulations application for such works.

As the open hopper is an existing feature of these properties and no Building Regulations application exists, we cannot require the homeowner to alter the drainage arrangement.

It is hoped that the information above answers any questions you may have but if you require any further information, then please email in the first instance.

Regards

**************
Registered Building Inspector
Office : 0116 272 7533

To book a site visit please use this link - Site Inspection Bookings www.lbcp.co.uk