At M.J. Robertson Plumbers we get a lot of enquiries about poor hot water pressure and lousy showers.

Most older homes have a low pressure hot water system where the hot water pressure is only about 10 to 50kpa, this is a bit like having the water fall from one to five metres above you whereas a mains pressure water supply is like having the water fall from around 50 metres above you!

Most modern tapware is designed for mains pressure systems and although some state “suitable for all pressures” they don’t always work that well on low pressure systems.

We often recommend to our clients to convert to mains hot water especially if their existing hot water system is over 20 years old, in most cases this is quite a straightforward job as we usually only have to remove the existing hot water cylinder and install a new mains option. Sometimes, however, the shower mixer needs to be altered or replaced to match the new mains pressure system.

The existing pipework is usually fine and would only leak if it, or one of its joints, was in poor condition in the first place.


Mains Pressure Storage Hot Water Cylinders

Replacing your old low pressure cylinder with a “Mains” cylinder is usually pretty straightforward and can be done in under a day.

One of the more popular conversions is to install an outdoor mains cylinder on the outside wall of the house. These cylinders are designed to be installed outside and will not only free up space inside your home giving you more storage inside but these installs can also work out cheaper than an indoor cylinder. With the cylinder located on the outside wall making access easy the long term maintenance and servicing will also be more economical and in the rear chance of something leaking at the cylinder there would be no water damage inside your house.

In my 35 years in the plumbing trade I have found hot water cylinders in all sorts of weird places like built into walls with no access, up in ceiling spaces again with very little access or just in a cupboard where the opening is more often smaller than the cylinder it’s self, in all of these cases the repairs would have been much easier and if the access was good and that is one of the main reasons why outdoor cylinder are becoming so popular.

Instant Continuous Flow Gas Hot Water (Gas hot water)

These systems are also a great option for mains pressure hot water and again are best to be installed on the outside wall of the house usually along with two 45Kg gas bottles.

Because these systems will keep suppling hot water endlessly they are a good option for very high uses of hot water.


Solar hot water is a fantastic option if you live in a warm climate and don’t have to contend with an OHS working at heights policy!

In Christchurch we wouldn’t recommend solar to any of our clients due to our low sunshine hours through half of the year, and a good quality known brand solar system is also very expensive.

We know there are a lot of cheaper systems on offer but anybody can import a solar system and sell it easily these days, but are parts, back up and service available in say five years time?

This along with the OHS working at heights laws, the less things on your roof the better as up-keep and servicing is just getting too expensive.


Air to water heat pumps.

This is still quite new to New Zealand but we do believe in the years to come this will be one of the main hot water heating systems in the country, in the same way home heating heat pumps have taken over a lot of the house space heating here.

As with most heat pump systems you get an average 3KW of heating for every 1KW you put in, making them very efficient.

Drawbacks could include a slow recovery time in cold climates and the need for an electrical element back up through the coldest months of the year.

Both solar and heat pump systems usually run through a larger type (200 to 300 litre) mains pressure storage hot water cylinder with the same set up as mentioned above.


These are rough estimates to give you an idea on supply and costs of these systems using only top of the line products backed by New Zealand companies and warranties.
Instantaneous gas $2,800 – $4,000 plus G.S.T
Mains storage cylinder $3,000 – $4,200 plus G.S.T

Solar indirect for cold climates $9,000 – $14,000 plus G.S.T.

Air to water heat pumps $6,000 – $8,000 plus G.S.T.

All these prices are exclusive of any electrical costs.