Annual inhibitor checks are vital for system protection, explains the HHIC

Published:  02 October, 2018

Annual checks of chemical inhibitor concentration help to ensure that ongoing protection is provided to the boiler and heating system against scale and corrosion. Neil Macdonald, Technical Manager at the Heating and Hotwater Industry Council, explains.

Regular checking of chemical inhibitor concentration, at least annually, is important to help ensure that ongoing corrosion and scale protection is being provided to the boiler and heating system.

Factors such as appliance or system repairs, which may necessitate the full or partial draining of heating system water, through to consumers removing radiators to redecorate (with the same effect), can all impact on correct inhibitor concentration and efficacy.

Dilution of the product to concentrations below the optimum level may place the boiler and system at greater risk from magnetite sludge as a direct result of corrosion.

All Heating and Hotwater Industry Council (HHIC) members who manufacture inhibitors volunteer their products for approval by NSF CIAS, previously known as BuildCert, which is referenced in the Domestic Building Services Compliance Guide to Part L of the Building Regulations in England. This ensures that they meet specified minimum performance levels for metallic corrosion and limescale inhibition, often exceeding them many times over.

Of key importance is that, when the system is originally installed and commissioned, or the boiler is replaced, the installer doses the system with the correct concentration of inhibitor to water. Then they should record on the Benchmark commissioning checklist details which product has been used, also applying the detachable sticky label, frequently supplied on the inhibitor container or packaging, onto the boiler, or another conspicuous part of the system.

This means that the next installer is able to quickly and easily identify the incumbent inhibitor. This is important, as established industry guidance is not to mix different inhibitors, to ensure that the active ingredients in different formulations do not work against each other in any way.

This also helps to ensure that if a top up of inhibitor is required (as should be indicated by a simple annual test of system water, most conveniently undertaken at the time of the annual boiler service), the system does not need to be drained to add the required dose, saving on time, labour, and cost for all parties.

As a system water sample is being taken, this is also an opportune time to assess the general cleanliness of the system water, and to clean the in-line system filter, which itself can often be used as convenient point in the system for sampling, topping up, or re-dosing.

Testing the concentration of system inhibitor is actually a very simple process, with most major manufacturers now offering bespoke test kits to assess their own specific products.

A full laboratory water test is a great option too, but it is recognised that this will need to be sent away for analysis and, if any concerns are identified, then a revisit will be required, meaning additional time and expense for all parties.

The HHIC wishes to help develop a solution which works for both the installer and their customer. As such, we have been actively working on an initiative with our water treatment group members to enable an annual test of various inhibitor products to be undertaken with a single test kit, focused on a single common element of all inhibitors – alkalinity.

Inhibitors are complex, mainly organic formulations, with individual ingredients providing protection for different parts of the heating system. These can be used up at different rates, dependent on materials of construction in the heating system, and will degrade over time.

As an ‘inhibitor check’ only focuses on one ingredient within the inhibitor, we have no way of knowing how the other components are functioning. In commercial systems, these individual ingredients are monitored four times a year, and re-dosed accordingly, but this would be nonsensical in the domestic environment.

Consequently, a full re-dosing of the system at set intervals (e.g. every five years) should be considered to maintain the efficacy of all inhibitor ingredients. Alternatively, a full laboratory water test could be carried out to ensure that system protection is being adequately maintained.

This project is a work in progress, but we believe that, when complete, it will offer the installer a simple route to compliance, as well as ensuring that their customer continues to benefit from the highest energy efficiency and lowest running costs that only an optimised heating system can provide. Additionally, they will receive robust protection against boiler and system breakdown, and peace of mind with regards the provision of any ongoing boiler manufacturers’ warranty.