Renewable Heating Hub Heat Pump Forums

Search with Wattson
Forums
Renewable Heating
Thermostats, Volumi...
Biocide and Inhibit...
 
Notifications
Clear all

Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!

Biocide and Inhibitor

 
Thermostats, Volumisers, Buffer Tanks, TRVs, Pumps, Piping, Valves, Radiators & Controls
Last Post by cathodeRay 8 months ago
9 Posts
5 Users
4 Reactions
958 Views
RSS
 Renewables345
(@renewables345)
Eminent Member Member
Joined: 12 months ago
Posts: 12
Topic starter 02/01/2026 12:38 pm   [#2700]

Hi all

I’m looking to get some insight on what others are using for biocide and inhibitor in air source heat pump systems. I am focused mainly on systems with AFV's, but could also do with some advice on glycol filled system too.

At the moment, we use R700 and X100, but we’ve seen some concerning press recently regarding these products. I’m particularly interested in:

  • What products you trust for preventing microbial growth in ASHP systems.
  • Recommendations for treating systems that already have spores or microbial contamination.
  • Best practices for preventing these issues from occurring in the first place.

Any advice, product recommendations, or experience you’ve had would be really appreciated!

Thanks in advance.


This topic was modified 8 months ago by Mars

   
Quote
Topic Tags
ASHP Biocide AFV
cathodeRay
 cathodeRay
(@cathoderay)
Famed Member Moderator
Joined: 5 years ago
Posts: 2991
03/01/2026 12:31 pm  

Can you specify what the 'concerning press' is? It may just be typical media scaremongering.

It is also a good idea to spell out what an abbreviation stands for the first time you use it. AFV? Armoured fighting vehicle? If so, that's a bit over the top for harmless bacteria.   


Midea 14kW (for now...) ASHP heating both building and DHW


   
👍
1
ReplyQuote
Toodles
 Toodles
(@toodles)
Famed Member Contributor
Joined: 4 years ago
Posts: 2942
03/01/2026 12:37 pm  

@cathoderay I took it to mean Anti-Freeze Valve.🤨 Regards, Toodles.


Toodles, heats his home with cold draughts and cooks food with magnets.


   
😂
1
ReplyQuote
cathodeRay
 cathodeRay
(@cathoderay)
Famed Member Moderator
Joined: 5 years ago
Posts: 2991
03/01/2026 12:40 pm  

Posted by: @toodles
↑

I took it to mean Anti-Freeze Valve

Possibly, given the context, but we don't know for sure. IDDAH to spell things out (it doesn't do any harm).


Midea 14kW (for now...) ASHP heating both building and DHW


   
👍
1
ReplyQuote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 6 years ago
Posts: 4837
03/01/2026 1:13 pm  

Posted by: @cathoderay
↑

Can you specify what the 'concerning press' is? It may just be typical media scaremongering.

It is also a good idea to spell out what an abbreviation stands for the first time you use it. AFV? Armoured fighting vehicle? If so, that's a bit over the top for harmless bacteria.   

I saw some chatter last year about general environmental impacts of biocides/inhibitors (potential for runoff or long-term aquatic effects if not handled properly when systems are flushed). 

 


🔥 Britain’s Heat Pump Shitshow
How Installing a Heating System Became a National Nervous Breakdown
Free UK shipping.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
New to heat pumps?
Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.


   
ReplyQuote
JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5322
03/01/2026 1:24 pm  

One school of thought says put almost nothing in and instead treat only to VDI2035 which is a German standard.  So far as I can see there is a lot to be said for this approach.  My cynical side says that, just like smart external controls, the industry may have developed and promoted products we don't need and never needed.


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
👍
1
ReplyQuote
Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 6 years ago
Posts: 4837
03/01/2026 10:53 pm  

@jamespa I share your cynicism.  I do suspect there’s a place for biocide I systems, but fully agree that VDI should be a far greater consideration.


🔥 Britain’s Heat Pump Shitshow
How Installing a Heating System Became a National Nervous Breakdown
Free UK shipping.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
New to heat pumps?
Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.


   
ReplyQuote
 Renewables345
(@renewables345)
Eminent Member Member
Joined: 12 months ago
Posts: 12
Topic starter 05/01/2026 8:54 am  

@cathoderay It is meant to be Anti-Freeze Valves. When I say concerning it is a bit of an exaggeration, but it is more to say that it isn't adding benefit to the system, and rather causing issue with these "spores". We've seen a lot of systems with strainers filled to the brim with them, and we can't seem to find a strong solution to stop this from happening.



   
ReplyQuote
cathodeRay
 cathodeRay
(@cathoderay)
Famed Member Moderator
Joined: 5 years ago
Posts: 2991
05/01/2026 9:32 am  

@renewables345 — thank you for the clarification. I'm rather aligned with @jamespa and @editor on this, the biocide products are more likely to be be solutions (sic) in search of a problem than anything useful. Inhibitors on the other hand probably do serve a useful purpose.

You can't normally see 'spores' unless they have somehow grown into something macroscopic. Has anyone looked at the debris in the filters under a microscope?


Midea 14kW (for now...) ASHP heating both building and DHW


   
ReplyQuote
Forum Jump:
  Previous Topic
Next Topic  
Related Topics
Topic Tags:  ASHP (88) , Biocide (1) , AFV (1) ,
Share:

SPONSORS

Join Us!

Installer Finder

Degrees of Separation

Latest Posts

SPONSORS

Members Online

Click to access the login or register cheese
Protected By
Shield Security PRO