Reply To: “Air”in hot water pipes.

In New Zealand we have similar problems. Typically the installation has a cold water relief installed which is relieving the thermal expansion. The problem arises when the cylinder is heating and giving off hydrogen gas, this gas forms at the highest point with no means of relief until a faucet is opened. I have found that the installation of an air emittance valve (usually used in radiator heating systems) at a high point usually fixes the problem.