Underground Inspection chamber base heights?

[Ruggers]

Does anyone know what the height/depth of a plastic base inspection chamber is for both 300 to accept 110mm pipe, and 450mm to accept 160mm pipe for foul & surface water?

Due to shallow fall over a long run to the mains, I need to keep the first inspection chamber from the house as close to the finished path surface as possible. I've allowed 300mm from the finished surface to the invert for the 450mm foul chamber. I'd prefer the surface water chamber to be shallow also.

Can the lid fit direct to a base or do they require so many spacer rings to avoid blockage?

 

[noseall]

Does anyone know what the height/depth of a plastic base inspection chamber is for both 300 to accept 110mm pipe, and 450mm to accept 160mm pipe for foul & surface water?

They vary, but all are bulky. In fact some of the smaller chambers sit taller than their larger mates. I'd say the shallowest sit at about 350mm from the deck and the deeper ones probably 450mm.

The lids are unlikely to sit directly onto the base unless they have a built-in riser. You can adapt the surround to suit the lids with mortar or header bricks if needs be.

 

[Ruggers]

Thanks @noseall The only dimensions i could find online was from Marley and they were showing the lesser diameter chamber bases higher than the 300 ones so it matches what you are saying. I find that strange. If need be I'll have to the first chamber so I can keep it to 300mm deep from cover to invert.

I was unsure if you need so much head room to the underside of the cover from the invert where a down pipe enters the chamber to prevent blockages.

What do you mean by adapting the surround to suit the lid?

 

[noseall]

What do you mean by adapting the surround to suit the lid?

The lid frame is unlikely to sit snug directly on top of the chamber base. It's usually moot in any case as the base normally sits with a slope suiting the fall of the pipes rather than obeying the surrounding paving.

What we do is slab all around the chamber then use mortar (building sand/screed sand/cement) to bench up around the chamber and allow the lid frame to squeeze into the mortar bed whilst using a 1200mm level to level it with the surrounding paving. You then remove the excess mortar and point it flush with the internal chamber. Then rinse away any droppings with copious amounts of water.

The whole lid bedding thing comes much later on when we start paving. It usually rests on the chamber until you are ready to pave.

 

[Ruggers]

I've used the method you describe when installing a rectangle lid frame to a brick chamber but always thought with the plastic frames that hold the lid, the round spigot had to fit inside of the round chamber risers to hold it all in place.

I see what you mean with the base sitting at the angle of the fall, the risers would need trimmed to an angle that matches the finished surface.

 

[noseall]

I see what you mean with the base sitting at the angle of the fall, the risers would need trimmed to an angle that matches the finished surface.

Correct. We do with an angle grinder - wearing shorts!

 

[Ruggers]

It's all good mate, your still here to tell the tale, thanks for your advice.

 

[noseall]

It's all good mate, your still here to tell the tale, thanks for your advice.

Just to add: The last few years our suppliers have been selling us an IC system (chamber bottom, riser, lid) where the lid has a black rubber seal that sits snugly into the riser as opposed to one that plonks on top. Couple that with a taller lid (more like a top hat), means that you have some height adjustment wiggle room. You just need to lube the rubber so that you can push or pull the lid without dislodging any risers.