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The Importance Of Seismic Restraints

Do you want this to happen to your cylinder?


If you don’t, seismic restrains are an excellent choice when installing your cylinder.

What are seismic restraints?
Seismic restraints for hot water cylinders are steel straps used to keep a hot water cylinder in place, preventing it from falling during an earthquake. They are affixed by screwes and washers of a certain standard to the wall framing around the cylinder. Hot water cylinders are heavy items, with a 135 litre cylinder weighing around 170 kg when it’s full of water. If there are no restrains, this is quite a lot of weight to be flung around in an earthquake, not to mention if you have an even bigger one. It can also damage other items such as pipes which are connected to it, and cause a flood.

Along with this, NZBC B1.3.2 standard requires building elements (including storage water heaters) to be adequately supported including support against earthquake forces. The method illustrated in Figure 14 is acceptable for water heaters up to 360 litre capacity. Where fittings and pipework are attached to the water heater through the supporting platform or floor a 50 mm minimum clearance shall be provided between the fitting and the support structure. 6.11.5 An alternative acceptable solution for securing storage water heaters against seismic forces is given in Section 203 of NZS 4603.


If you are getting a new cylinder installed, make sure that it comes with a seismic retraint kit!

Retrofitting a seismic restraint kit
If you already have your cylinder installed and are not looking to replace it anytime soon, it is possible to retrofit seismic restraints to your exisiting cylinder. However, this is more complicated than installing with a new cylinder, since access behind the cylinder is required. If this is something you would like to do, it is best to contact us to discuss the job.