This method statement has been written as a guide for cleaning of existing domestic central heating systems using a Fernox Powerflow Flushing unit in conjunction with Fernox cleaning products. System cleanliness is checked using a Fernox Total Dissolved Solids (TDS) Meter

1. Method statement for Fernox powerflushing of
existing domestic central heating systems
Powerflushing using the Fernox Powerflow Powerflow flushing unit. Failure to do so will prevent
Flushing Machine MKII the waste water flowing to drain and may result in
With the exception of some boiler changes (see notes overflow of the Powerflow tank. If necessary, the
above) power flushing with the Fernox Powerflow Powerflow flushing unit can be elevated to increase
flushing machine should be undertaken after completion the fall on these hoses. Care should be taken to
of any installation or repair work. ensure the Powerflow flushing unit is well supported
and stable.
Preliminary Checks 12. Isolate the circulator pump and, if a Fernox
1. Fill the system, vent all high points, pumps and Powerflow Pump Head Adapter is available,
radiators. (Sealed systems should be filled to their remove the pump head and connect the adapter
normal working pressure) to the in-situ pump body. Alternatively remove the
2. Check for leaks and repair as necessary system circulator and connect the adapter elbows
supplied with the Powerflow unit across the pump
System Preparation connectors. Couple the pump head adapter, or the
3. Turn off all electrical controls and electrically isolate adapter elbows to the yellow flow/return hoses. For
the system combination boilers where a pump head adapter is
4. Note the setting of each valve before opening them, not available, connect by fitting the ¾" Powerflow
so that the system can be re-instated after flushing. flow/return hoses directly to the main system flow
and return or across a radiator. Connecting across
5. Open all radiator valves to their maximum setting a radiator will reduce flow rate and may affect the
and remove TRV heads to ensure maximum flow efficacy of the power flush.
through the valve.
13. Isolate the electricity supply to the system circulator.
6. Set diverter or zone valves to manual. If in doubt, seek the advice of a qualified electrician.
7. Anti-gravity valves (non-return valves) if fitted should 14. Connect the power lead on the Powerflow flushing
be bridged, by-passed or temporarily removed. unit to the electricity supply via an RCD.
Set-Up and Connection of the Powerflow Flushing Operation of the Powerflow Flushing Machine MKII
Machine MKII 15. Turn on the mains supply and fill the vessel to
8. Always employ best practice when protecting between the maximum and minimum marks.
customer’s property for wet works.
16. Open the flow and return valves and allow the unit
9. Connect up the ½" clear mains water inlet hose, to run for 15 minutes with all radiator valves open,
¾" clear dump and overflow hoses and ¾" yellow reversing the flow regularly.
rubber flow and return hoses to the Powerflow by
their Cam-lock connectors. Connect the Flushbuddy 17. Dump the dirty water to drain whilst adding clean
between the flow/return valve and the hose using the water to the reservoir tank until the TDS of the
Cam-lock connectors provided. The direction of flow dump water is within 20% of the incoming mains
for the Flushbuddy is not important. water.
10. Ensure that the isolating valves on the flow and 18. Refill the system and add the Fernox cleaning
return hoses, mains fill and dump valve are all in product of choice to the Powerflow Flushing Unit
the closed position, and that the waste hose and via the chemical addition port. Open the mains
overflow both terminate in a foul drain. water inlet valve and fill with water to approximately
half way between the maximum and minimum
11. Ensure that the dump hose and overflow hose liquid level markers on the reservoir. Close the
both drain to a point below the dump valve on the mains water inlet valve.
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2. Method statement for Fernox powerflushing of
existing domestic central heating systems
19. Open the system pump isolating valves and the five minutes. The system water should be green in
flow/return isolating valves on the Powerflow colour. If the water is still red, more neutraliser will
flushing unit. Ensure that the dump valve on the need to be added.
Powerflow remains closed.
30. Open the dump valve on the Powerflow flushing
20. Switch on the machine on the power supply to the unit to send the water to the foul drain.
Powerflow flushing unit.
31. Open the cold water supply to the unit and regulate
21. As necessary, control the water level in the reservoir to ensure the water level stays above the minimum
via use of the mains water inlet valve, ensure that mark, this is to ensure that the flow of water
the liquid level in the reservoir remains between the entering the unit is equal to that leaving the unit. If
minimum and maximum liquid level markers. the mains water pressure is low, the dump valve
should be partially closed to compensate for the
22. Switch on the boiler and allow the central heating
reduced flow rate of the mains water.
system to reach operating temperature.
32. From a convenient supply point, take a sample
23. Allow the unit to run for 1 hour, reversing the flow
of the mains water and measure the total
regularly. Identify any cold spots on radiators, or
dissolved solids using the Fernox TDS meter.
blockages during this time.
Note the reading on the Fernox power flushing
24. If the system has an indirect cylinder, divert the flow monitoring sheet.
to the cylinder coil and circulate for 10 minutes,
33. Flush the system and allow the water to run to
reversing the flow regularly. Divert the water back to
waste until it appears clean. Turn off all radiator
the heating circuit.
valves except for the last radiator to be cleaned,
25. Close off all the radiator valves except for the and continue flushing until the wastewater
radiator furthest from the Powerflow flushing unit. appears clean.
26. Allow the unit to pump through this radiator for 34. Take a sample of the wastewater and measure
a minimum of 5 minutes or until even heat is with the Fernox TDS meter. Compare the meter
achieved over the radiator surface. Reverse the reading from the wastewater with the previous
flow regularly during this time. Cleaning time will mains water reading. Continue flushing and
vary depending on the extent of debris and sludge sampling the wastewater until the reading obtained
within the radiator. Tap the radiator with a rubber with the TDS meter is within 10% of the mains water
hammer may help to dislodge any debris. sample.
27. Close the flow and return on the radiator and 35. Note the TDS reading from the radiator on the
then move to the next radiator. Open the valves Fernox powerflushing monitoring sheet.
and repeat radiator clean. Continue until all of
36. Close-off the radiator, move to the next and flush to
the radiators have been cleaned. When all the
within 10% of the mains. Record the TDS reading
radiators have been flushed, open up the valves
on the power flushing monitoring sheet. Radiators
on all radiators.
should be flushed in the reverse order to which
they were cleaned. Repeat until all of the radiators
Draining the Powerflow Flushing Machine MKII have been individually flushed.
28. Switch off the boiler.
37. When all the radiators have been cleaned, divert all
29. If Fernox DS40 System Cleaner has been used, the flow to the indirect cylinder coil (if present) and
add the Fernox System Neutraliser via the flush until the TDS of the dump water is within 10%
chemical addition port and circulate for a further of mains.
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3. Method statement for Fernox powerflushing of
existing domestic central heating systems
38. Open all of the radiator valves and continue to flush 46. Fernox Protector level should be checked on an
until the wastewater is within 10% of the mains. annual basis. This can be undertaken as part of
an annual service using either the Protector test
39. Verify that the system has been adequately cleaned
reagent within the Fernox Water Test kit, or using
and flushed by undertaking the chloride and
the Fernox laboratory postal service.
copper tests within the Fernox Water Test Kit.
Protecting and Re-Commissioning the System
40. After the system water has been confirmed as
being within 10% of the mains, close the mains
water supply and switch off the Powerflow flushing
unit. Close the system circulator isolation valves
and disconnect the unit from the heating system.
The Flushbuddy can be cleaned ready for re-use,
by rinsing under flowing water.
41. The system should be immediately protected
by adding Fernox Protector F1. If the engineer
chooses to add the Fernox Protector F1 via the
chemical addition port of the Powerflow, care must
be taken to ensure that the Fernox Protector F1 is
fully dispersed before disconnecting the machine.
This will take a minimum of 15 minutes.
42. Re-connect the system circulator and restore the
electrical supply to it. Remove any temporary
connections or caps and reset the valves to their
operational positions.
43. Install the replacement boiler if necessary. (see
notes on boiler change)
44. Fernox Protector F1 is supplied with a sticker
to indicate the date of treatment and the product
used. This should be completed and placed on the
boiler casing in a convenient location to allow future
engineers to identify the treatment regime used.
45. Verify Protector level is adequate using the Fernox
Protector Test Kit within the Fernox Water Test
Kit. Underdosing of an inhibitor can lead to a
reduction in the protection of the heating system.
Overdosing of an inhibitor will not have any adverse
effects on the heating system. If necessary, add
additional Fernox Protector F1.
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