News has hit the grapevine than the inhibitor F1, made by Fernox, a market leader in water treatment chemicals, can be used with softened water.
In general, we shouldn't trust rumours, but the public release of the information has come strieght from the horses mouth -
we received a PDF press release, originally from fernox explaining the details a little bit. The technical bulletin states:
"In January 2013, the water treatment group of HHIC approved the following statement concerning the use of water softeners:
Where a water softener is present in the dwelling ensure that a heating system primary circuit is filled with mains water via the general bypass valve as required within BS14173. Note: A water
softener must comply with BS14173 (this states that there must be ‘a general bypass valve which
enables the softening unit to be isolated from the mains, while maintaining water supply to the
end user’. For installation requirements, refer to WRAS Information and guidance Note No 9-07-
01 “Information for the installation of ion exchange water softeners for systems supplying water
for domestic purposes”.
Refer to boiler manufacturer’s instructions for any additional advice on softened water."
Consequently any future central heating installation where a water softener is present should not be filled with softened water.
The DWTA support this advice, however there will still be some existing installations where the primary circuit has already been filled with softened water. For these installations, the following advice is still relevant.
When a central heating system is filled with base exchanged softened water, Fernox Protector F1 will adequately protect the heating system as long as it is correctly dosed and maintained t
throughout the life of the system. The correct dose rate of Fernox Protector F1 can be verified
using either a Protector Test Kit or a Fernox System Health Check, both available from plumbing
This recommendation is identical to that given for natural waters and indicates that Fernox Protector F1 inhibits in all water conditions."