Water Softener Installation on a private water supply

Installation guidance and notes on Sodium

Many boreholes will supply water containing high levels of hardness. Where the hardness exceeds 200mg/l a water softener should be installed to protect water heaters and reduce energy consumption. 

Sodium is added to water as part of water softening and other ion exchange processes. The taste threshold concentration of sodium in water depends on the associated anion and the temperature of the solution. At room temperature, the average taste threshold for sodium is about 200 to 300 mg/l. Levels above 400mg/ are unsuitable for irrigation as the sodium may burn the leaves of plants. The level of sodium in 1 litre of softened water at 300 ppm hardness (very hard water) is 136mg and therefore the sodium in softened water cannot be tasted. 

No health-based guideline value for sodium has been set by the World Health Organisation. Claims that softened water is harmful to health lack scientific rigor as the recommended daily intake of sodium for a person on a normal diet is 2300mg, on a low-sodium diet, 750 mg. Even a person on a no-sodium diet is expected to consume 250mg of sodium a day. A glass of milk contains around 170 mg of sodium.

Water softener installation

The regulations relating to the type of materials and fittings connected to the distribution system apply to the public water companies and do not relate to private water supplies which are governed by the private water supply regulations. The private water supplies regulations for England and Wales do not give any guidelines regarding the installation of a water softener which means there is no requirement to install a separate drinking-water tap for practical or health-related considerations.

cabinet water softener
Installing a water softener

This is also true for public supplies unless the sodium level of the softened water exceeds 200 mg/l – but a separate hard water tap is recommended by the Department of Health, the Water Supply Companies and the UKWTA for infant feed preparation and where residents may be on a medically prescribed low-sodium diet.

For more detailed information regarding the installation of water softeners refer to the WRAS Information and Guidance Note No 9-07-01. Information relating to water hardness and health can be found in the UKWTA position paper “Drinking Water Hardness and Health”.

Geoff Nemec MSc (Eng) MCIWEM CEnv

Updated Sept 2021