How to: dose inhibitor and cleaner into a central heating system

About the problem

Many of Sentinel’s water treatment products come in a variety of formats, each with a slightly different application technique. The Rapid-Dose format comes with its own dosing adaptor and instructions. Products in concentrate format also come with an adaptor and these are applied using a traditional caulking gun. Since our liquid products don't come with an adaptor, we are most often asked how to get them into a system and we recommend using a Sentinel Dosing Vessel or similar device.

The solution

Here’s a step by step guide to dosing systems with liquid products using a Sentinel Dosing Vessel:

1. Ensure that pump and boiler are off by isolating the power.
2. Open systems: dosing can be effected via a radiator or any dedicated dosing point in the pipework.
3. Sealed systems: the filling loop serves as an additional convenient dosing point.
4. To inject into a radiator: Isolate the radiator and drain sufficient water from it to enable the bleed pin (or the whole fitting) to be removed without spilling water. The bottle should not be pressurised at this time.
5. To inject the additive via a filling loop: May require the draining of some water from the system, as, in a sealed system, water cannot be displaced to make room for the additive. The maximum operating pressure of the bottle is 18 psi (1.23 bar), so unless the system is very large it is advisable to drain off approximately the same amount of water as there is additive to be dosed.
6. Fit the appropriate dosing adapter to the radiator (or filling loop) and connect the bottle hose to the adapter.
7. Remove the bottle plunger assembly from the bottle. This is done by twisting the plunger anticlockwise. Empty the additive into the bottle, observing all handling precautions.
8. Reassemble the bottle and pressurise by operating the plunger no more than 30 depressions.
9. Open the radiator valves (or filling loop valve).
10. Release the additive into the system by opening the fluid flow valve on the flexible hose. Observe the fluid level falling in the bottle. If necessary, the plunger should be operated to empty the bottle completely. In the case of a radiator, a small volume of air should be allowed to enter the system - this will ensure that when the adapter is removed, no water will spill out
11. Close the fluid flow valve.
12. Close the radiator valves (or filling loop valve) and release any remaining pressure in the bottle.
13. Open the fluid flow valve. In the case of a radiator, this will release any air back into the bottle. If the operation has been carried out properly, no water will be displaced into the hose and bottle.
14. Loosen the hose connector and remove the adapter. If applicable, refit the radiator plug, open the radiator valves and vent the radiator.
15. Switch the power back on and recommission the system.

After leaving the premises, release any air pressure in the bottle to the atmosphere, and store any unused additive. Do not use the bottle to transport additive.