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Simplex softeners

Simplex water softeners, or single column water softener, are best suited to steady demand applications up to moderate capacities for the domestic and commercial market. (Industrial and other larger demand systems often use Duplex softening – please see technical data sheet 2023). Regeneration is programmed to occur during low water usage periods, typically 2am, however instantaneous regenerations systems are available.

During the regeneration cycle, simplex systems will normally bypass hard water to service to maintain supply unless otherwise specified. Generally, simplex softeners will need to be sized to give at least on day’s supply of softened water output before regeneration.

These types of softener are very reliable and give many years of good service with minimal maintenance. They are, therefore, extremely cost effective.


Softener control valves are sized and specified according to the flow rate required by the application. The inlet and outlet connection ports generally range between ¾” to 2” for standard control valves, with flow rates up to 18m3 per hour. We also supply systems for higher flow rates where required.

Steady demand applications are suitable for either time control or volume control. Variable demand systems are better served by using volume control via in-built metering.


Fundamentally, the size of a water softener is governed by the amount of exchange capacity that is required for the application. The capacity of ion exchange resin is a function of the volume of water that passes through it and the hardness of the incoming water. The chart below shows the capacity of each size of softener assuming the feed water has a hardness of 300mg/litre (21° Clarke). The volume can be adjusted on a pro-rata basis for different levels of hardness.

Another important criteria to consider is the continuous flow rate required. This affects the size of valve that can be used, and sometimes the size of the resin column since the water needs to have a minimum contact time with the resin to achieve full softening. Short term higher peak flows can be tolerated, but this sometimes results in a low level of hardness passing through into service and can increase the pressure drop across the softener. At design flow rates you can expect a pressure drop of between 10 to 15 psi. Usually, all automatic water softeners need a minimum water pressure of 25 psi and can operate up to at least 100 psi.

All these softeners require an electrical supply. 240 volt or 24 volt are standard.


Note: To prevent damage to the vessels this equipment must be protected from negative pressure from the drain or the supply. A vacuum release valve is recommended on the inlet supply and is supplied by us on all equipment using vessels of 370mm diameter upwards. The maximum water temperature permissible is 45°C.


Automatic water softeners need a supply of appropriate salt to make the required brine for regeneration purposes. Salt is most commonly supplied in 25kg bags of either granular or pellet type. This type of salt is manufactured specifically for water softening purposes and has a very high purity level. Sometimes, on very large systems, PVD salt can be supplied in bulk. Other types of salt should not be used due to the levels or impurity or additives.

The only attention required from the use is to check, on a regular basis, that the level of salt in the brine tank is kept topped up to ensure a saturated brine solution is available for regeneration.

Although softeners are very reliable, as with any other piece of essential plant, routine servicing is strongly recommended. This is generally straightforward and will ensure many years of reliable service from the plant.