Gas Water Heaters and Hard Water or Borehole Water

Water hardness – Hard water contains a higher than normal concentration of Calcium and Magnesium, along with various other minerals. Soft water has either had the minerals purified out of it or it is fresh surface or rain water that has not come into contact with minerals. Excessive hardness may change the taste of drinking water, cause soap and detergent not to bubble and clog or stick to plumbing or appliances.

The minerals in hard water tend to stick to the inside of plumbing pipes and appliances. This coating of minerals is called ‘scale’. The formation of this ‘scale’ is more pronounced when the water is heated and may cause the pipes to get clogged or the appliances to malfunction or be permanently damaged.

Both gas and electric water heaters are affected by scale. It prevents the efficient transfer of heat from the heating element to the water to be heated – this may mean it costs more to heat up the water. The build-up of scale will also eventually make the water storage capacity less. This will also affect the flow of water passing through the water heater, restricting hot water output.

Palomas’ Gas Water Heater heat water by passing cold water through a copper Heat Exchanged. This heat exchanger is manufactured from very high quality copper – due to copper’s properties of high conductivity and physical strength. Due to the very high heat values (upward of 46kw) within the heat exchanger, hard water minerals will stick to the interior of the copper pipes with the heat exchanger. This will eventually clog up the heat exchanger and prevent it from working properly. If not rectified in time the heat exchange will eventually rupture.

Ground water / Borehole water – Groundwater occurs underground within certain layers of rock. It is abstracted from these water bearing layers via boreholes or wells. With boreholes a thinner deep shaft is sunk into the ground and the water enters by flowing sideways through the perforated holes in the shaft. Wells are shallower and wider and the water flows upwards from the bottom of the well.

In some areas of South Africa, groundwater meets SABS drinking specifications. However, because water pollutants and contaminants can move from the surface into the ground, the quality varies greatly from area to area and is therefore directly affected by activities in the area e.g agriculture, industry, sewage etc. The degree of pollution changes very slowly.

Surface water – Just like groundwater, surface water is affected by activities in the area. Surface waters may contain many different pollutants but not in high quantities. But the degree of pollution may change rapidly.

Options for dealing with hard water / groundwater

As each situation is different – the water needs to be tested and filtration built to specification. Yearly re-testing of water should take place due to the changeable nature of borehole water. Please check your manual for any specific water requirements.

Water quality is VITAL to the operation of your Paloma Gas Geyser. Therefore to ensure longevity and validity of your warranty, the composition of water being used within the unit should not exceed the following parameters: 

pH 6.5 to 8.5
TDS (Total Dissolved Solids) Up to 500 mg/L
Total Hardness Up to 200 mg/L (11.7 gpg)
Aluminium Up to 0.2 mg/L
Chlorides Up to 250 mg/L
Copper Up to 1.0 mg/L
Iron Up to 0.3 mg/L
Manganese Up to 0.05 mg/L
Zinc Up to 5 mg/L


Borehole water affected Paloma Gas Geyser
Borehole water affected Paloma Gas Geyser

Paloma Gas Water Heaters should be flushed every 3-6 months to try to help preserve the appliance and its unique parts. 

We would also recommend you to flush with vinegar to remove scale build up.

You will need 5-10 litres of standard vinegar, a submersible pump, 20 litre bucket and washer/dryer hose set.

Click here to get instructions on how to flush your geyser

The use of Borehole Water will invalidate Paloma Gas Water Heater’s warranty.

Please see more on our GWH warranty page


Paloma’s Gas Geysers must be installed in accordance with the below advice, to be covered by the Paloma warranty.

Our gas geysers are manufactured to suit the water conditions of most public reticulated water supplies. However, there are some known water chemistries which can have detrimental effects on the water heater and its operation and / or life expectancy. If you are unsure of your water chemistry, you may be able to obtain information from your local water supply authority. A Paloma gas geyser should only be connected to a water supply which complies with these guidelines for the Paloma warranty to apply.

Change of water supply

The changing or alternating from one water supply to another can have a detrimental effect on the operation and / or life expectation of a heat exchanger in a continuous flow water heater.

Where there is a changeover from one water supply to another, e.g. a rainwater tank supply, bore water supply, desalinated water supply, public reticulated water supply or water brought in from another supply, then water chemistry information should be sought from the supplier or it should be tested to ensure the water supply meets the requirements given in these guidelines for the Paloma warranty to apply.

Saturation Index 

The saturation index (SI) is used as a measure of the water’s corrosive or scaling properties. The saturation index figures stated are calculated using a water temperature of 80°C.

In a corrosive water supply, the water can attack copper parts and cause them to fail. Where the saturation index is less than –1.0, the water is very corrosive and the Paloma warranty does not apply to a copper heat exchanger in a continuous flow water heater.

In a scaling water supply calcium carbonate is deposited out of the water onto any hot metallic surface. Where the saturation index exceeds +0.80, the Paloma warranty does not apply to a copper heat exchanger in a continuous flow water heater.

Water which is scaling may be treated with a water softening device to reduce the saturation index of the water.

Saturation Index of Gas Continuous Flow Geysers

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