One-way 'check' valves
One-way ‘check’ valves (or non-return valves) are a plumbing device which stops the back-flow of water in your plumbing system. They are often used when adding appliances such as washing machines or dishwashers to the plumbing.
Here is an example of a one-way 'check' valve
Some taste and smell issues with your water can be caused by rubber or plastic fittings connected to washing machines and dishwashers when they are plumbed into pipework before your taps. This can sometimes give chemical, rubber, plastic or ‘TCP-type’ tastes or smells to your water.
By installing a one-way ‘check’ valve or non-return valve where these appliances are fitted, the water which is left standing in the plastic or rubber hose cannot flow back into the water supplying your tap, which should resolve your issue.
A good way to test if you need to install a one-way ‘check’ valve is to try closing the valves where your washing machine or dishwasher is connected to the water supply and see whether the taste and/or smell problem persists. For advice on how to do this, please see the image below.
Ensure the washing machine or dishwasher is not in use. Turn off the isolating valve (A) for the cold water hose. (Usually, the hose or the valve will be coloured blue). Place a bowl or jug underneath to catch any water.
If this resolves the issue, we recommend that you install a one-way ‘check’ valve between the cold water pipe and flexible hose that feeds the appliance. You can request one below.