Header Tanks & Hot Water Cylinders

Hot water supply systems that were installed in the 1940s-60s most often had a ‘header’ or ‘supply’ tank that was fitted in the roof space or in some cases the ceiling. If these low-pressure systems are still in use, they may have insufficient pressure to run some modern bathroom fittings. Header tanks need to be installed at a higher level than the cylinder to increase pressure, generally, the higher the header tank, the better hot water pressure a dwelling will have. Most often they are located in the ceiling space but sometimes they will be located on the roof. All header tanks should have a lid installed to prevent any unwanted items entering the tank.

Header tanks without lid

Header tanks are generally made of polythene, copper, or concrete. Due to their weight it is recommend seismic restraints are installed especially if they are concrete. Concrete header tanks were often used in state houses and are very heavy. In the event of an earthquake they have potentially to fall over and fall through the ceiling, this would put people inside the home in danger. Some roof spaces will have a redundant header tank present when a dwelling has upgraded to a mains pressure system. They are difficult to remove from a ceiling space due to the large size. Even if the header tank is not in use, it is recommended seismic restraints are installed or the tank is removed if possible.

If a water heating system has a header tank it will also have a hot water over flow on the roof. This will look like a tall metal pipe and depending on its height, should have stays fitted to ensure it does not move in the wind and damage the roof. During inspections we sometimes find hot water overflows that are leaking onto the roof. This typically occurs due to the NEFA valve being adjusted to increase the water pressure. We recommend this is remedied by a suitably qualified plumber.

Overflowing cylinder

If a hot water system has a header tank and overflow still in use the hot water cylinder will most likely have been replaced. If the hot water cylinder was replaced after 1992, it is a requirement for seismic restraints to be fitted so that it does not fall over during an earthquake. If the hot water cylinder is less than 200L it will require two seismic restrains – one at the top and one at the bottom, if it 200L or over it requires three restraints. Seismic restraints can be bought for around $50 and installed as a DIY job.  For hot water cylinders installed before 1992 it is still highly recommended restraints are present although they were not a requirement at the time of installation.

Low pressure hot water systems often have a long lifespan although tend to be upgraded to mains pressure or infinity systems when they are at the end of their life. This is because water flow is faster and water can heat up quicker with more modern systems.

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