Underfloor heating inhibitor.

7 May 2014
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United Kingdom
We have a Daikin Air Source heat pump feeding our hot water and under-floor 8 port manifold heating system.

The Daikin has just had its annual service and the engineer commented that the water looked discoloured and that the inhibitor needed replacing??

Is this an easy procedure? I'm pretty savvy at DIY so is it something I could do myself?

I've tried to find a local plumber but seems they're not interested (too small a job??)

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The inhibitor/antifreeze wouldn't normally need replacing, it doesn't get replaced as such. Either there wasn't enough or any to start with and the system has now corroded to the point whereby it has started to darken the system water.

System will need drained, flushed and then re-inhibited/antifreezed correctly.
Thanks. Daikin recommend 1lt of Fernox F1.
Not sure I'm up to draining the system?????
I'll try and find a plumber!
Does the water have a greenish tinge?
I was recommended to use X700 biocide (Sentinel products).

I added this through the magnaclean filter, a simple process, scoop out the water with a small glass... and then bleed the air out.
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Thanks. Daikin recommend 1lt of Fernox F1.
I believe they also recommend certain levels of glycol too, given the ASHP is in the South though I am unsure as to whether the area is exposed to extended periods of sub zero temps? If there is any risk of that then a certain level of antifreeze would be recommended and may have been added when commissioned. That antifreeze(AF) must contain inhibitors as glycol can accelerate corrosion. Who installed the system as there should be a clear record of the commissioning and what fluids/additives were used initially.

If a glycol base AF was used then that could have used up all the inhibitor over time. If it was used then as part of the service was a PH test performed, should be and the results documented? That may be what the engineer was meaning.
Thanks Madras. The internal unit is in the garage so not exposed to freezing conditions.
The house was built in 2015/16 and the plumbing was done by a "Devon Plumbing" which I wouldn't recommend to anyone!!
It's taken five tyears to sort out all the leaks and correct all the mistakes! Even now, on this last visit the engineer found that there is no magnetic filter installed and the bypass is the wrong side of the esbee valve so that has to be corrected!
More thinking about the outside unit. AF always needs to be considered if the external unit can be subject to freezing conditions. If so the wet side of the system can be susceptible to freezing.

When it come to draining and flushing I would leave that to someone that is experienced with those system TBH
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