A heads-up on header tanks
Selywn District Council media release: 1st May 2024
Now is a good time to retrofit seismic restraints around your home...
Roof space and roof top water tanks (or header tanks) are more common than you might think, and a large proportion of these are still not properly restrained against earthquakes.
There is an estimated 232,000 header tanks in roof spaces and 59,000 on roof tops according to the Building Research Association of New Zealand (BRANZ). Approximately 93 percent of these are not properly restrained.
Header tanks can be potentially dangerous in an earthquake - even if they are no longer in use - as they can fall through the ceiling or off the roof.
Building Code clause B1 requires water tanks including header tanks to be adequately supported including seismic restraint chocks. Retrofitting restraints to older tanks where they do not exist is highly recommended.
Some ready-made kits are available from hardware stores that include galvanised or stainless steel straps, screws, tensioning devices, earthquake brackets and bolts for header tanks up to around 700 litres.
Another option is to install 25 x 0.75mm or similar galvanised or stainless steel restraining straps, fixing the tank to roof framing to prevent it overturning or falling off the roof in an earthquake.
Extremely small tanks of less than 90 litres can be restrained with blocks around the base and a single strap around the tank. Use two straps for cylinders of up to 200 litre capacity and a third strap in the centre for larger tanks. The top and bottom straps should be no more than 100mm from the ends of the cylinder.
Contact the Selwyn District Council building team for more information on header tanks (0800 SELWYN - 0800 735 996 or contactus[at]selwyn.co.nz).