Plate Heat Exchanger - Limescale

Hi All,

I had the PHE replaced about 18 months ago as it was blocked with scale on the mains side. In the last weeks, I had noticed the hot water flow rate decreasing so I took out the PSE myself and found it blocked again. I managed to descale it and refit and all now seems good.

Just some questions:

- Aside from a proper water softener; what do you recommend as a scale inhibtor? Are the inline inhibitors effective at all? Currently there apears to be nothing fitted.
- On the thermal store side of the PSE, it was really clean. Also around 18 months ago, Glendhill replaced the off peak heater and had to fully drain/refill. I assume they added an inhibitor when they filled it back up. I lost some water during the PSE replacement, the return pipe to the store was dripping as I couldn't get the valve to shut off. I am just wondering, if I need to top on the inhibitor and if it's safe to use Fernox considering I don't know which inhibitor Glendhill used? Or is it better to drain/refill and some point. Might be worrying for nothing, as I suppose I only lost some litres but the water is so hard here!

Cheers,
Frank