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Explanation of the safety valve with overpressure caused by hot weather

My gas tank whistles in hot weather, why?

The summer is almost upon us, so one can never be too careful about the safety of a gas tank. It may be the case that your gas tank reacts to the hot weather and the safety valve mechanism operates. This can be heard and seen by a whistling sound and sometimes also a small white cloud escaping from the safety valve.

What is a safety valve and what does it look like?

A safety valve makes sure that any overpressure in the tank can automatically and safely escape. It must be replaced every ten years.

The safety valve is assembled on the tank on a valve support or directly on the tank itself. On the safety valve there is also a protective cover to prevent the penetration of moisture/dirt. With underground tanks the valve is usually assembled on the service valve. On an aboveground tank the safety valve is not under the protective cover.

When is there the likelihood of overpressure and how does the tank react?

There is a likelihood of overpressure in very hot weather or with overfilling. In hot weather the liquid propane in your tank has a greater tendency to change to a gaseous state. This extra gas causes a higher pressure in the tank. With persistent or extremely hot weather the pressure can increase until we have overpressure.

The tank will indicate overpressure in two ways:

  • The dial shows an increase
  • The safety valve opens and allows the pressure to escape (smell of gas + sounds + protective cover is blown off)

What must one do in the case of overpressure?

  1. Cool the tank with water (eg with a garden hose), until the safety valve closes automatically when the pressure has dropped sufficiently.
  2. Place a wet cloth over the tank as long as it stays warm.
  3. Put a parasol over the tank when the sun is shining. Place the parasol so the tank is in the shade, but do not put it over the safety valve.

How can one prevent overpressure?

  1. In the summer only fill the tank to a maximum of 75% so there more space in the tank for the build up of gas without causing overpressure.
  2. Maintain the tank well so the reflective light-green paint stays visible
  3. Create shadow, temporarily with a parasol or by planting a green hedge around the tank (taking account of the compulsory safety distances)

Important to know:

  • A safety valve that opens is not a defective safety valve. The safety valve just does what is intended for, to allow excess gas to escape. So it does NOT HAVE TO BE REPLACED.
  • When a safety valve does not close properly after blowing off pressure (there is still a leak), the safety valve MUST BE REPLACED. Immediately contact the gas supplier/owner of the tank.