Your O’Three Advanced P-Valve has been expertly fitted to your suit and is supplied to you with the Dome Cover turning freely. This will allow the non-return valve which sits under the dome cover to operate unhindered.

It is this non-return valve that allows urine to exit, whilst preventing water from entering the P-Valve tube.

The Dome Cover

The Dome Cover is not required to operate the valve.  The purpose of the dome cover is to protect and if necessary, block the non-return valve.  Please ensure that the dome cover is turning freely in normal use.


In the unlikely event that the non-return valve fails, simply rotate the dome cover clock-wise, lightly tightening until it stops. This will block the mushroom valve and stop any further ingress of water. Do not over tighten.

If you are diving, but not connected to the valve, another reason for diving the valve in the block position, is if you were using your suit for buoyancy.

Depending on your “trim”…, air might escape through the valve.  Simply block the valve as explained above.


The parts of the valve that are on the inside of your dry suit are at ambient pressure (balanced).

To ensure that ambient pressure is achieved to the externally parts of the valve, it is good practice before you enter the water to return the Dome Cover to its original free turning position when you dive connected to the valve.

By doing this, it will ensure that every part of the valve is balanced and therefore working effectively.

APV Care and Maintenance Video

APV Care and Maintenance Leaflet