A beginner's guide to performing kitchen sink plumbing

While you may want to leave the majority of your plumbing installation to a qualified professional, there are a few small areas of work that you can carry out yourself. With that in mind, here is a beginner's guide on performing some basic kitchen sink plumbing.

How your plumbing system works

Your home's water supply system delivers water under pressure to fixtures and appliances such as bathroom sinks and kitchen appliances whether they are ceramic sinks, double sinks, granite sinks or even copper sinks. The soil and vent pipe (SVP) system relies on gravity to carry liquid and solid washes to the main house drain which slopes down to a sewer pipe or septic tank. U-shaped traps in the drain pipe of most fixtures hold water that acts as a seal to keep sewer gases from entering the house.

Rodding eyes

Rodding eyes or clean-out plugs in the main and branch drains provide access for clearing blockages. Vent pipes connected to the drainage system allow sewer gases to escape and help to keep trap seals in place.

Earthing metal pipes

All metal pipework must be joined to the house's main earth bonding system to prevent electrocution from touching a pipe that has become live through an electrical fault. Ensure that you have an earth strap fitted to your pipework near where it enters the house with a length of earth core leading back to the main earthing point. If a live wire touches a metal pipe anywhere in the house, the current will be conducted through the pipework and will be safely earthed.

Water needs to drain downhill

Drainage pipes won't drain efficiently if they aren't fitted with the correct 'fall'. Whenever you plan to install a new fitting, particularly a kitchen sink or shower where the waste outlet is already close to the floor level, make sure that the waste pipe can slope down sufficiently to where it joins the main drain pipe or exits the wall. Installing pipes A pipe should fall by no less than 20mm for each 1m in length, but no more than 50mm for a pipe less 1m long or 25mm for a longer pipe. To prevent self-siphoning, a standard 32mm drain pipe should be no longer than 1.75m. If your pipe needs to be longer than this, use a larger 38mm pipe which can be up to 2.3m long. Take advice from your local building control officer if you need to exceed this length.