How to increase hot water pressure

Sounds like an easy job. 

“Hey Mr. Plumber, can you increase my water pressure please?”

In fact there are some considerations before you can ‘wind-up’ the pressure.

If you have a low pressure hot water cylinder the easy answer is, “get a mains pressure cylinder”, but it is actually not that easy. Sometimes changing the cylinder type results in sub-optimal operation of shower mixers as they have been set up for unequal pressure. In this case you will have to make very minute adjustments to get the temperature you want in the shower. Otherwise this can actually be a great option. 

Another option in the same realm as changing to a mains pressure hot water cylinder is to install an instantaneous water heater. In this case you will need to find a way to get gas to the place you need whether it be LPG in bottles or town supply.

If you don’t want to change the cylinder, there is an opportunity to change your valve pairing, or increase the ‘head’ of your cylinder by increasing the height of the copper pipe sticking out from your roof.

There are 3 low pressure valve ratings, 3.7m, 7.6m or 12.2m. These inform you of how much pressure you can get out of your cylinder. The most common we have seen is 3.7m and 7.6m.

Low pressure valve delivers

3.7m = 3.7 x 9.8kPa = 36.26kPa

7.6m = 7.6 x 9.8kPa = 74.48kPa

12.2m = 12.2 x 9.8kPa = 119.56kPa

For reference, a mains pressure cylinder should deliver anywhere from 350-500kPa

You’ll note that these low pressure cylinders put out poor pressure, if you compare it to mains pressure cylinders.

The problem is, that you cannot always just change your valve to a higher value. Your cylinder is designed to take a maximum pressure, so sometimes you cannot increase the size of the valve.

To add more complexity, there are 2 types of low pressure cylinder set ups. Valve vented and open vented. 

Valve-vented require a pair of valves. The limiting valve and the relief valve.

Valve-vented low pressure hot water cylinder

Open-vented only has a limiting valve, and a tall copper standpipe on the roof of your house which gives your house the head of pressure. 

Open vented low pressure hot water cylinder

So as you can see, it’s not so easy. Should you want some advice, don't hesitate to contact us by phone, email or simply fill in our contact form.