Agreed @johnmo - a combined product can tackle multiple issues simultaneously.

I'm just providing the link to that Flomasta product from Screwfix.

Before you buy, check everything:

For example, the usual dosage of a typical corrosion-inhibitor would be about 1%.
But that Flomasta combined inhibitor and anti-freeze requires 25% concentration for their base-level protection down to -11°C
... and it costs £40 for each 5-litre container.

Does your Village Hall system have a dosage-pot to better facilitate adding large quantities of chemical?

@editor  Thanks for your help.

@transparent  Before the antifreeze option came up Corrtec was the suggested additive. I don’t know about acidity but we are on mains water - no limescale. Batteries ? do you mean in conjunction with PV. We are looking into getting PV at the moment.                                                                                                   I’m hoping to talk to the engineer who serviced it shortly. Lots more q’s now. No dosage pot that I’m aware of presumably engineer will be kitted out for large scale dosing. One final question a separate issue about ASHP installation pipework, in our case the primaries are 28mm plastic which are insulated directly near the 2 pump units – mounted on a concrete platform. However they - 4 x28mm pipes are then bundled together uninsulated and run down into a duct through the platform below ground across a pathway and up into the plant room 3-4m run approx. It strikes me this can’t be good for the system performance. I think it would be possible to re- run the pipework separated & properly insulated just below or above ground level but would it make a big difference?

Great.... This is the sort of related information we need @toucan

Don't worry about grammar, or trying to organise the issues...
... just fire them all out and we can take it from there!

Batteries, PV panels and overall system resilience are best discussed in a separate/new topic within the Energy Storage section of the forum.

We need a topic title which brings in the right sort of people in future. Something like "Energy generation and storage for Village Hall" is sufficiently all-embracing.
I'd like to propose parts of the work which could be done by the village community rather than just buying-in expensive contractors.
That also has the advantage of people in the village picking up new knowledge and skills which can then be applied to their own houses.

Yes, your preferred heating engineer may have a pump which can be used to push larger quantities of additives into the system.

Just bear in mind that any future breakage which requires the system to be drained down will mean throwing away some very expensive chemicals!

My own house has 340-litres of circulating fluid, so I'm very conscious of migating against such a scenario.

You are absolutely right to raise the problem of uninsulated plastic pipes for the main feeds into the building.
That should never be the case, whether they're underground or ducted or sleeved.

Any chance of some photos?
I'd be particularly interested to see the point where they enter the 'thermal envelope' of the main building.

Posted by: @transparent

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My own house has 340-litres

That's a lot of water, think I have 60L in my 195m² slab. 

It is indeed a lot of water @johnmo

But my starting point is a 280-litre thermal store!

Whenever I've needed to release water to 'work' on the heating system, I've perfected a method of temporary storage using a large rainwater tub on a wooden platform in the bathroom!

The same trick isn't likely to work for a village hall.
But it's something to consider before @toucan spends £hundreds on an expensive chemical solution.

On the note of glycol performance effects; my Vaillant Arotherm Plus system is augmented with 10% Fernox HP5c additive. According to the manufacturer’s specs, at this concentration it only reduces the heat capacity of the water mix by ~2%, which to me is a worthwhile trade off for the peace of mind knowing I don’t have any anti-freeze valves which may suddenly dump all the fluid, or not work when needed.