How to Cut an Inspection Chamber Riser

An inspection chamber is an essential part of any drainage system, as it provides access to the underground pipes for inspection, maintenance, and cleaning. Sometimes, you may need to cut an inspection chamber riser to change its height or to fit it into a narrow space. Cutting a drainage chamber riser is not a complicated task, but it requires some care and precision.

In this article, we will explain why you might need to change the height of your inspection chamber, the tools you will need, and how to cut it in a few simple steps.

Why adjust the height?

Several scenarios might require you to adjust the height of your inspection chamber, such as:

• Landscaping changes: If the ground level around your inspection chamber has changed due to landscaping, paving, or other reasons, you may need to adjust the height of your chamber to ensure it remains accessible for inspection and maintenance.
• To comply with regulations: Depending on the location and type of your drainage system, there may be certain regulations that specify the minimum and maximum height of your inspection chamber. For example, in the UK, the Building Regulations 2000 state that the inspection chamber should not be more than 600 mm below the finished ground level and not less than 150 mm above the invert level of the lowest pipe. Delve deeper into inspection chamber depth regulations with our helpful guide here.
• Drainage and slope: If you're adding an extension to your drainage network, the existing chamber might need adjustment to accommodate the new pipework. In some cases, lowering the chamber can help improve drainage flow within your system.

Read more about the diverse uses of inspection chambers in our article here.

Things you’ll need

To cut an inspection chamber riser, you will need the following components and tools:

• An inspection chamber base: This is the bottom part of the inspection chamber, where the pipes connect. You can choose from different sizes and shapes of inspection chamber bases, depending on the number and diameter of the pipes you have.
• An inspection chamber riser: A riser extends the base of the chamber vertically to ground level. You can choose from available heights and diameters depending on the diameter of your chamber base and the height you need.
• An inspection chamber cover: This is the top part of the inspection chamber, which closes the chamber. You can use a round or square inspection chamber cover, which can be made of plastic, galvanised steel, cast or ductile iron, or concrete, and can have a load rating of 3.5 to 40 tonnes.
• Measuring and marking tools: A tape measure, spirit level, and marker pen will help ensure accurate cuts.
• Cutting tools: Depending on the riser material, you can choose a handsaw, jigsaw, reciprocating saw with a metal blade, or an angle grinder with a diamond blade. You can also use a file or sandpaper to smooth the edges of the cut.
• Sealant: To maintain watertightness after cutting, use a suitable sealant for the specific material of your riser. Some chambers may have a ring seal, in which case sealant will not be needed.
• Safety gear: Gloves, safety glasses, and a mask are essential to protect yourself from dust and debris.

How to cut an inspection chamber riser

Our inspection chamber risers can be cut using the following steps:

1. Measure the height of the chamber base and the height of the inspection chamber cover. Subtract the height of the cover from the height of the base - this will give you the maximum height of the riser that you can use.
2. Mark the desired height on the riser using a marker pen and ensure that the mark is level and straight. If you're using a Floplast riser, which features grooves at 60mm intervals to accommodate the ring seal, you'll have to make sure you cut in accordance with these grooves. There's also an additional 55mm at the top of the riser than can be used for fine adjustments.
3. Cut the riser along the mark with a handsaw or a reciprocating saw. Make sure that the cut is clean and smooth - then you can use a file or sandpaper to smooth the edges of the cut. Some specialist risers might have specific cutting instructions, so always refer to the manufacturer's guidelines before proceeding.
4. Apply sealant or silicone to the inside of the riser's cut end to form a watertight seal between the riser and the base. Some risers require a rubber gasket for a watertight seal, so always consult the riser instructions for proper placement.
5. Insert the cut end of the riser into the base and push it down firmly. You can use a rubber mallet to tap the riser into place. Make sure that the riser is aligned with the base and that there are no gaps or cracks between them.
6. Place the cover on top of the riser and secure it with the locking mechanism. You can use a screwdriver or a spanner to tighten the screws or bolts that hold the cover in place.

By following the steps above, you can cut an inspection chamber riser safely and effectively to the desired height. If you're unsure about any of the steps, seek advice from a qualified plumber or drainage specialist. Remember to consult the manufacturer's instructions for your specific inspection chamber model, as some designs might require cutting at a different point.