cold water softened, hot water still quite hard

[Question]

I had a water softener (Tapworks)  installed a few months ago.  The softener feeds both the cold and hot water.  When I test the cold water, it is soft (40 ppm). When I test the hot water is quite hard (180 ppm).  When I test the bypass cold water, it is extremely hard (1000 ppm).

 

I have an unvented cylinder with a Worcester-Bosch boiler.  I have just adjusted the water softener for much harder water (it was set for 270 ppm and is now set for 500 ppm, the max), and I hope this will change the hot water hardness -  I will have to wait until the tank is refilled.  

 

Why is the hot water harder than the cold water?

[Russdl]

I seem to recall reading somewhere that the soft water will slowly remove the scale from the tank so that may be what is happening, the soft water going to the tank is coming out harder because it is bring scale out with it when you run the tap. If that is the case you won’t get soft hot water until that process is complete. 
 

Found it from the Harvey website

Edited November 6, 2022 by Russdl
Added hyperlink

[Question]

Thanks for the reply.  The softener and the unvented cylinder were installed at the same time.  However, your explanation may make sense as the hot water pipes have had years of hard water and would be filled with limescale.