Dose & Fill® Pressurisation & Dosing Unit

From £3,250.00 £3,900.00 inc. vat


Dose & Fill® has been developed to combat the growing costs and problems associated with heating systems starved of inhibitor. Modern systems frequently have aluminium heat exchangers, steel panel radiators & thin copper tubing, requiring adequate levels of inhibitor to avoid perforations, blockages and to validate the manufacturers’ warranties. Traditionally a system is manually dosed via a dosing pot after the initial fill. However, this is diluted every time the pressurisation unit adds plain water following normal minor losses or after partial draining for maintenance. Dose & Fill® is a compact & wall mounted filling and automatic make-up unit for adding water to a sealed system. The Dose & Fill® incorporates the Arrow Valves Midi-Fill Digital® pressurisation unit, whilst the lower half of the 1 m tall enclosure contains a 20 litre chemical container. In “Auto Dose” mode, the unit monitors the quantity of water added by the pressurisation unit and then the dosing pumps automatically inject inhibitor into the heating system according to concentration set via the LCD digital display. The correct concentration is therefore maintained. Dose & Fill® has been designed to comply with the Water Regulations, providing Fluid Category 5 backflow protection for filling and top-up of “non-house” heating or systems.


Filling, topping up, initial and continued automatic dosing of- Primary Heating Systems LTHW; Under Floor Heating; Refrigerating Equipment; Chilled Water Circuits; Industrial Processes.

Product Specification
  • Backflow Prevention Yes
  • Powered Yes
Specification Clause

The primary sealed heating system shall be filled and pressurised by a Dose & Fill pressurisation & automatic dosing unit – model DF22[1] – as manufactured by Arrow Valves Ltd – Tel 01442 823123 . The unit shall have two digital control panels with a pressure transducer monitoring the system pressure. The controller shall have three volt-free relay outputs for – boiler run with high and low pressure cut-out, general fault and combined warning and fault. The fill rate shall be 1000[2] litres per hour @ 1 bar pressure differential. The unit shall feature a built-in electronic water meter with a volt free warning relay, which shall activate should the monthly consumption exceed 50[3] litres per month.

The unit shall be wall mounted at a serviceable height with the digital control panel accessible and visible. The automatic filling device is to be connected to the mains water supply or, where the mains supply pressure cannot maintain 1 bar dynamic, from the boosted cold water service if available. The manufacturer’s flexible hoses incorporating a servicing valve and inlet strainer shall be used. A double check valve is not required.

The high cut-out pressure shall be set upon commissioning to 0.2 bar below the safety relief valve pressure. The cold fill switch-on pressure shall be 0.2 bar more than the static head of the system. The unit shall automatically set the low cut-out to 0.5 bar below the cold fill pressure.

The outlet from the unit must be connected to the primary circuit return before the circulation pump. A 22 mm warning pipe must be connected to the overflow and discharged into a gully in a conspicuous manner.

The unit shall incorporate an automatic dosing unit for injecting inhibitor into the heating system. Twin dosing pumps shall draw chemical from the internal 20 litre container. The user shall set the concentration via the LCD display panel according to the inhibitor manufacturer’s specification.

The system must be thoroughly flushed, pressure tested and drained before final filling. The unit shall be filled with Sentinel X100 inhibitor at a concentration of 1%[4].

The system shall be filled from empty in “Auto Dose” mode. Once filled and circulated, the inhibitor strength must be tested in accordance with the manufacturer’s instructions.

The primary heating system expansion shall be accommodated in an air charged Expansion Vessel – model EVCP – as distributed by Arrow Valves Ltd – Tel 01442 823123 The vessel body shall be mild steel with red epoxy coating with a bottom entry male connection. The butyl membrane shall be suitable for 99 degrees Celsius at 6 bar (for 80 litres and larger). A separate expansion vessel ball valve with wire lock, drain tap and union – model BVEV – shall be supplied to enable draining of the vessel in order to periodically check the air charge. The vessel must be correctly sized[5]. The pre-charge pressure shall match the cold fill switch off pressure.

Amend as required
[1] 22 denotes the supply size, also available in 15 mm (e.g. for boilers less than 200 kw) code – DF15
[2] 720 (for 15 mm version)
[3] Value between 20 – 1000 litres per month.
[4] Consultants normal BSRIA or similar specification……………Fernox F1 at a concentration of 0.5%.
[5] Where possible specify quantity and size of vessel(s)

Data Sheets


dfdatasheet-2.pdf (1.01 MB)


Installation Guide

dfommanual.pdf (1.37 MB)


Additional Information



Approval Certificate

2209317-MFD-DF-1.pdf (104.68 KB)