How To: Change a pressure relief device (PRD)

A pressure relief device (PRD) is a small but vital safety feature of an electric shower. If one goes, how can it be replaced?

How To 7 February 2017
How To: Change a pressure relief device (PRD) image 1 - Two popular PRDs: Triton 83301330 (left) and Triton 82800450.
Two popular PRDs: Triton 83301330 (left) and Triton 82800450.

Pressure relief devices (also known as pressure relief valves, and shortened to PRD or PRV) are small but vital safety features of electric showers.

If water is unable to be fully discharged through the shower head, pressure can build up in the heater tank, which could prove to be dangerous. In such situations the PRD will blow, allowing this pressure to escape. As a result, you may notice a small leak from the bottom of the shower body.

Blown PRDs need replacing. Before this, however, you should establish the cause of the PRD blowing in the first place to prevent the problem from reoccurring. If the original fault is not addressed, the new PRD will blow immediately upon installation as well. Common causes are:

  • Shower head blocked with limescale and debris. An easy way to unblock a shower head is to use a good descaler.
     
  • Kinked or damaged shower hose, or one that has collapsed inside. Unfortunately, in these cases, the hose will need replacing.
     
  • Less commonly, but not unheard of, is a sudden increase in the cold mains supply.

Fitting a pressure relief device is a straightforward process, but you must follow all safety guidelines or consult a trained plumber/electrician. Electricity and water supplies to the shower must be off before proceeding. Our video below gives an overview of the process:

From our video, general instructions are as follows:

  1. After following all necessary safety precautions, take off the front cover to the shower.
     
  2. The pressure relief device will be located near to the outlet pipe (possibly right at the bottom). It may or may not be fixed on with screws.
     
  3. Unscrew the PRD if applicable, not forgetting to also take out the old O'ring left inside if it doesn't come out with the PRD.
     
  4. Place the new O'ring (supplied with the new PRD) into the opening and then screw on the new PRD if applicable. You may need a little force in order to push the device in initially, but don't use excessive pressure. The new PRD will have a small rubber ball inside; this is absent from the old device as it would have blown out.
     
  5. Restore the front cover and water/power supplies to the shower. Test as needed.

Triton offer a large range of electric showers in the UK, and as such, the Triton 82800450 (shown in the video) and Triton 83301330 pressure relief devices are widely-mentioned parts.

We offer a great value NSS shower head descaler to help with blocked shower heads, one of the leading causes of PRDs blowing.

You can also read about the most common problems with electric showers.

Visit our YouTube channel here for more guides and tutorials.

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