Clack V4099 External Blending Valve WS1/WS1.25 and Clack Heads 1191 and 1190FP Refill Head

The V4099 is Clack's external blending valve, fitted to WS1 and WS1.25 control valves as well as the 1191 and 1190FP refill heads, to blend a controlled proportion of raw hard water back into the softened output. This is used where fully softened water isn't wanted for every purpose - for example to reduce sodium content, soften the "slippery" feel of zero-hardness water, or meet a target residual hardness. The valve is externally adjustable, so the blend ratio can be tuned without opening the control valve itself. Stocked by WrekinWater as a genuine spare or upgrade part.

Technical specifications

Symptoms that mean you need this part

• You want to reduce the residual hardness of softened water rather than run at zero hardness
• The existing blending valve is stuck, leaking or no longer adjustable
• You're fitting a blending function to a WS1/WS1.25 valve or 1191/1190FP head for the first time
• Output water hardness doesn't change no matter how the blending valve is adjusted, suggesting the internal mechanism has failed

Why it fails / why it matters

Some households and commercial sites prefer a small amount of residual hardness in their softened water rather than the zero hardness a softener produces by default, whether for taste, to reduce sodium intake, or to avoid the very slippery feel of fully soft water. The V4099 achieves this by diverting a proportion of raw water around the resin bed and blending it back into the softened supply, with the ratio set externally via the valve's adjustment. Like any adjustable valve, the internal seals and adjustment mechanism can wear or seize over time, at which point the blend ratio becomes unreliable or fixed regardless of adjustment, and replacement is the straightforward fix.

Why buy this from WrekinWater

WrekinWater has supplied genuine Clack valve accessories for over 15 years from its Bettisfield, Shropshire base, stocking the V4099 alongside the full range of Pentair Fleck, Autotrol and Kinetico components so you can fine-tune your softener's output hardness with the correct part. Rated Excellent on Trustpilot, the business has served more than 50,000 customers and dispatches orders quickly.

How to fit it

1. Isolate the softener at the bypass valve and relieve pressure before working on the valve body
2. Locate the blending valve fitting on the outside of the WS1/WS1.25 valve body or 1191/1190FP refill head
3. Remove the old or faulty blending valve, checking the mounting port and o-ring for wear or debris
4. Fit the V4099 blending valve into the same port, ensuring the o-ring seats correctly
5. Restore the water supply and check the fitting for leaks before adjusting the blend ratio to your target
6. Test the output water hardness with a hardness test kit and fine-tune the valve's adjustment until you reach the desired residual hardness