Choosing a Hot Water System: Storage Tank or Continuous Flow?

17 May 2018    Hot Water

The next decision, after heating method (see Choosing a Hot Water System: Electric, Gas or Solar?), is whether you go for a system with a tank, or one that heats water as needed.

Storage tank

Most electric, gas and solar hot water systems use a tank.

Mild-steel tanks can corrode over time; maintenance every few years can help prevent this. They usually have five- to 10-year warranties. Feel free to give us a call at On Tap if you would like us to service your hot water system.

Stainless steel tanks are more expensive, but generally last longer and don’t require as much maintenance as mild-steel tanks. They usually carry a 10-year warranty, but still require occasional maintenance (such as replacement of valves and seals).

Local water quality may dictate which type is best for you; feel free to give us a bell at On Tap to discuss which option is best.

Tanks are insulated, but there is always some heat loss over time, so it’s good to install them in a sunny spot or in an insulated space.

Continuous flow (‘instantaneous’)

Also often referred to as “instantaneous”, a continuous flow HWS heats only as much water as you need, when you need it. They aren’t truly instantaneous – it can take a few seconds before hot water starts flowing from the tap, especially when there’s a fair distance of pipe between the HWS and the tap.

Most models use gas, but electric models are available.

As there are no heat losses as with water stored in a tank, they’re often cheaper to run than storage systems.

The size you need (flow rate in Litres per minute) depends more on the number of hot water outlets the heater has to serve than on the number of people in the household. As a general rule, for a two-bathroom house you need a flow rate of about 22–24 L/min. Talk to us at On Tap Plumbing and Gas Perth to find the right capacity for your home.

We’ve had clients advise that their continuous flow water heaters were not turning on because of a combination of low flow shower heads and too high a trigger point for the hot water heater to start up; essentially, the water flow was not sufficient for the water heating to be triggered. Keep this in mind if you are considering having low-flow shower heads and a continuous flow hot water heater, and confirm the trigger point is set appropriately.