Reliability of Fernox Express Inhibitor Test Strips

[sharpener]

Because the price of the official pots of 50 of these test strips is so high I bought a packet of five for £6-99 from ebay, arrived without instructions or colour matching chart.

 

The online instructions say read the strip within 10 seconds but they showed little colour by then. However a dark brown shade developed after about 30 secs. Google AI says this means they are time-expired or contaminated.

 

The system was power flushed before the HP was fitted in 2024 and Adey inhibitor and biocide added afterwards. I am not particularly concerned but both years since, the Vaillant service technicians have said that they do not test inhibitor strength.

 

Should I be worried? Should I return them to ebay and claim a refund? Are THESE PHP tests at £3 per test any better? Is there an alternative?

 

TIA.

[SimonD]

I have the Adey kit and use it quite a lot actually - works well and is reliable. When I bought my kit which comes with the charts - 1 per test strip, the big pack of test strips were out of date so I emailed my supplier and they arranged replacement directly from Adey. Once I ran out of in date ones and used the out of date ones and they were still fine.  

 

Technically it's now a service requirement on most if not all gas boilers and heat pumps. I'm sometimes surprised when systems I installed and dosed correctly show low levels of inhibitor, but it happens even after just a year sometimes.

I'm not sure how often most systems get tested. I went through a phase of testing every new gas boiler I serviced and ran a good top-up business for a while until I stopped taking on new customers. As for Vaillant technicians not testing, well that's pretty much a given, but just wait until there's a warranty claim - as customers of mine who became my customers learned when their hex started leaking on a nearly new Glow-worm and the installer wasn't interested. Vaillant/Glow-worm visited and told them they wouldn't touch it unless they could provide a certificate that the system had been flushed to BS standards and that inhibitor had been added (even thought the system was leaking) - queue them calling me.