Corroded zone valve replacement

30 Nov 2010
Reaction score
United Kingdom
Hi guys,

My HW started heating up whenever the CH was on. I diagnosed a faulty zone valve on the HW side (old Drayton model). I have an S plan unvented system. I pulled off the actuator for the HW valve, but when the valve was manually closed it still charged the HW tank. I plan to change both valves for Honeywells, but the CH valve in particular is really corroded at the pipe joints. Also the HW valve seems to be blocked from above with a few drips of solder. I assume I can release the corroded CH valve by cleaning of the excess crap, using a penetrating lubricant and a load of elbow grease? Re the HW valve, can you 'mop' up excess solder by heating it first, or is this risky? I've added some pictures below. Thanks for any help you can offer. Rob.
CH zone valve. Nov 2020.jpg
HW zone valve. Nov 2020.jpg


  • CH zone valve. No actuator. Nov 2020.jpg
    CH zone valve. No actuator. Nov 2020.jpg
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  • HW zone valve. Nov 2020.jpg
    HW zone valve. Nov 2020.jpg
    490.9 KB · Views: 54
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It will be mostly lime scale, a bit of grunt normally shifts them, you could try soaking in white vinegar or better still a product like Limelight or Viakal, soak and wrap a bit of soaked rag around the joint then leave overnight.
Cheers buddy, will try that. Gonna give it a go at changing these suckers tomorrow (or the wife will murder me if I keep the heating off!).

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