Inspection Chamber Installation Guide

Inspection chambers allow access to drains for inspection, rodding and jetting. For this reason, inspection chamber installation should be carried out at a maximum interval of 22 metres along straight pipe runs and wherever there is a horizontal bend of more than 30 degrees, an intersection or shift of direction, a variation in the pipe diameter or any other notable changes in the system.

Follow this basic step-by-step inspection chamber installation guide to ensure your chambers are fitted correctly. 

Preparing the site

Before starting your inspection chamber installation, it’s important to ensure the site is suitably prepared. This involves a few simple steps: 

• Choose your location - first of all, you need to choose a suitable location to install your chamber, such as at a change in direction, a pipe intersection or a shift in gradient 
• Excavate a pit - next you need to excavate a pit 300mm wider than the chamber and make sure the base will sit below the frost line to prevent freezing (around 600mm-1200mm) 
• Lay bedding - before lowering the chamber into place, lay a level bed of compacted pea shingle roughly 150mm-225mm thick 
• Align the drainage pipes - before finalising your installation, you also need to ensure the pipes are fully aligned 

Assembling the inspection chamber

Before you can install your chamber, you’ll need to assemble it: 

• The inspection chamber base is provided with a series of inlet and outlet holes covered by blanking plugs. Align the base so these fit correctly with your inlet and outlet pipes, removing the blanking plugs from the holes you will be using. Leave the blanking plugs in any holes that won’t be used – these incorporate a seal that will ensure the chamber remains watertight
• Apply universal joint lubricant around the inner top edge of the chamber
• Add further lubricant to the groove in the first riser section that will hold the rubber seal
• Carefully fit the seal into the groove of the riser section, ensuring it is fully located (some inspection chambers have an integral seal within the riser section, in which case the above two steps are irrelevant)
• Apply lubricant to the outside of the seal to fully coat the rubber
• Insert the riser section into the base section, rotating the riser section 180 degrees in one direction and back to ensure the rubber seal is evenly distributed around the full circumference. Apply firm downward pressure to complete the seal

Adding dirt and debris barriers 

At this point in your inspection chamber installation process, you may want to consider adding a MuckStopper 450 from Drainfast. Designed especially for the 450mm internal diameter of standard inspection chambers, this acts as a temporary barrier to dirt and debris on the building site, preventing it from entering the drainage system where it can cause blockages.

Brushes around the circumference of the MuckStopper create a seal with the chamber walls that will halt larger debris but allow water to pass through, while a bucket in the centre catches finer debris and silt. The MuckStopper remains in place until the drain installation is complete and the inspection chamber lid and frame are ready for permanent fitting.

When this time comes, the MuckStopper is simply raised in the chamber using its extraction rods. Any debris on the brushes can be moved to the central bucket before the MuckStopper is fully removed, leaving behind a clean and debris-free chamber. The MuckStopper can then be emptied, cleaned and redeployed for another inspection chamber.

• Repeat the above steps with further riser sections to bring the inspection chamber to the required depth. The corrugations around the outer chamber walls serve as a useful template for cutting riser sections to the correct height, using a fine-toothed saw
• The inspection chamber frame and lid can now be added

Connecting the inspection chamber to your pipework

When you look at an inspection chamber base you will notice a central channel running straight from one side of the chamber to the other. On either side of this will be angled channels, looking a bit like the branches of a tree. The ‘trunk’ of this tree is the main channel for your pipework, with the inlet at the top and the outlet at the base of the tree. The branches are additional inlets for other pipes that may be required to enter the chamber, forming a junction.

Installing an inspection chamber on a straight, level run of pipe is simple: just connect the ‘upstream’ pipe to the inspection chamber inlet and the ‘downstream’ pipe to the outlet. But what if you need to place the inspection chamber at a point where the pipe changes direction or is on a gradient? Find out in the next section of our inspection chamber installation guide. 

Installing an Inspection Chamber at a Change of Direction

Don’t be tempted to use one of the side branches for your main pipe run if you are turning a corner – these are only to be used as spurs for incoming additional drains and with their tighter angles and change in gradient are more likely to cause a blockage if you do try. The main route of the pipe should always run through that main central channel.

If you are wanting to turn a 90-degree bend, this is the correct way. Set your inspection chamber at 45 degrees to the angle of the bend. This will give you a long bend which is less likely to cause blockages. Use 45-degree pipe connectors at the inlet and outlet to create a finished 90-degree turn.

A 45-degree bend can be achieved by setting the inspection chamber parallel to the incoming pipe and adding a 45-degree connector to the outlet.

This means that if the pipework needs to be accessed from the inspection chamber you will only have to negotiate a 45-degree bend at any point.

Inspection chamber installation on a gradient

The key point to bear in mind here is that the inspection chamber should always remain vertical, as the fall in the chamber has been designed for level installation.

To get around this problem, use pipe bends to angle the inlet and outlet pipes, twisting them and rotating the inspection chamber until you achieve a satisfactory angle of entry and exit while maintaining a constant downhill flow.

How deep can an inspection chamber be?

To comply with building regulations, a standard 450 mm diameter inspection chamber can only be 1.2 metres deep. An adoptable inspection chamber can be installed up to 3m deep.

Any inspection chambers installations over 1.2m deep will need a restrictor ring to reduce the access to 350mm. Depending on the type of cover or riser used, these are fitted into the frame of the cover or over the top of the riser.

Do I need to use seals on an inspection chamber?

Regulations require seals between the separate components of an inspection chamber to keep it intact and prevent percolation into the surrounding soil in the event of the chamber flooding.

Some chambers will come with the seals pre-installed, whereas some will need to be fitted with a seal before placement. Make sure to check whether your chamber needs seals before installing it.

Inspection chambers at Drainfast 

Hopefully, this complete inspection chamber installation guide has covered everything you need to know. If you have any further questions, you are always welcome to call the friendly team of drainage experts at Drainfast on 01420 555600, email [email protected] or fill out our contact form.