Bath Plumbing and Heating

Power Flushing removes the debris that can accumulate and assists to cause blockages in pipework

The following photos illustrate the equipment used during a 'power flush' and a blockage (cathode) due to corrosion and electrolysis; the later being quite common in open vented heating system pipe work, although the following photo illustrates a good example of an extremely bad case, unfortunately we are not 'Super Man' with x-ray vision, the section of pipe containing the cathode (that had formed) needed removal, no viable (cost effective) amount of power-flushing would have cleared the obstruction, but the skills of an experienced plumbing and heating engineer. Excessive amounts of flux and their not being neutralized and flushed out after installation, and a lack of anti corrosion inhibitor, and or the affects of (electrical) earth leakage earth bonding may have all contributed to this situation of a blocked expansion / cold feed pipe. Doing away with the feed & expansion tank and replacing it with an unvented system prevents the regular ingress of air that assists corrosion.

When having your boiler changed, it is advised (a requirement) that a power flush be performed on your old existing system.
The reason for this is that modern high efficiency boilers have much smaller heat exchangers; and are prone to blockage: especially the plate heat exchangers on combination boilers, which can act as a filter, become blocked and effect the production of domestic hot water*.

• The effect being:
• To restore comfort
• Save fuel bills
• Help reduce global warming

*Not referring to lime scale blockage due to hard water; it is advised that that all combination boilers installed within hard water areas are protected by a Combimate or similar water conditioner.

Symptom of blocked domestic hot water heat exchanger(HW HE) = (cycling) Causing the domestic hot water tap to run very hot then very cold -

On older heating systems, especially those that once incorporated a "feed & expansion tank" then sludge will be present as well as other contaminants such as "flux". It may be that the boiler being replaced is a combination boiler at the end of its serviceable / working life, and that; it replaced a boiler that had its primary (water) circuit vented to atmosphere. During this previous time of replacement a proper flush may not have been performed.

It has been stated that 75% of boiler manufacturer call backs to replacement boiler installations are associated to contamination / debris as the cause.
Not having a heating system properly flushed may affect the boiler manufacturer's warranty.
Power flushing units may incorporate a heating unit; the time factor involved to heat the system during the flushing process could be reduced and the procedure different where it is possible, it may be useful, to use the existing boiler to provide heat to assist in performing the flush every situation is different.
The duration and method of work will vary and be dependent on the individual circumstance of installation.

If a radiator develops a leak anywhere, other than at a connection; it is a good indication of corrosion within the whole installation: an inspection at the "feed & expansion tank" can provide a good indication of the internal condition, especially if honest & accurate installation / service history is available.
If replacing a radiator due to leakage / pin-holing; close inspection of the failed radiator may be a useful indication to the general condition of the heating system.

The most common telltale sign of corrosion is the black inky sludge, magnetite, found when removing a radiator; this black gel can be prevented by a good quality anti-corrosion inhibitor.
It is fact that if an "open vented" boiler is replaced by one of a "sealed system" (mains pressurized) a greater internal system pressure will be developed during operation affecting any weak or poorly jointed pipe and fittings. This could be a consideration, when selecting a replacement boiler.

Manufacturers, such as Valliant and Worcester, produce an open-vented (to atmosphere) condensing boiler; therefore with this boiler there is no noticeable increase of working pressure within the pipe work installation. Parts of a system that have failed due to severe corrosion may become apparent, during the power flushing procedure.
Whilst power flushing will enhance the efficiency of an old dirty heating system: The pressure developed by the machine is a little more than that developed by the average domestic circulator (pump) but not greater than the pressure of which a properly installed and sound system, should be capable of handling.

The normal power-flushing process is not detrimental to sound pipe work and joints; in simple the process merely sloshes the cleanser water solution back and forth in a controlled manor to loosen any debris which can then be rinsed out. All power flushing pumps should incorporate a magnetic filter such as Adey's 'MagnaClean' to intercept any iron residue. When the process is complete a quality anti corrosion inhibitor system protector should be added to the primary heating circuit.

Control valves may be used during the process of a power flush that haven't been operated for many years or merely of cheap quality. They may start to leak if used (it happens with new valves); if this happens during a power flush, the engineer, though not at fault, would endeavour to assist the home owner, to resolve the problem.
The worst culprits for causing problems, specific to heating applications, is the ¼ turn ball type valve; whilst they are excellent for gas and cold fluids when they are used on central heating systems they are unreliable, a gate or globe valve is a safer and more reliable alternative the former tend to leak from the area of the screwdriver slot when disturbed (used) even when not, whilst a gate or globe valve may leak on use the gland can often be repaired, little can be done, but replace, when a ¼ turn valve starts leaking.

A good level of knowledge in "plumbing & heating" will assist in a successful power flush: reducing the likely hood of problems occurring, and being able to deal with them should they occur. The purpose of a power flush is to remove any iron oxide particles and foreign matter that causes deterioration, blocked pipes and radiators, thus inefficiency (bad heat transfer) of heat from radiators.

I have been called to properties, where several plumbers had recommended a power flush, and it was not the case, all that was required was a simple understanding of heating systems.
One final point, avoid placing replacement boilers in roof spaces where possible, in particular when attached to old pipework systems; the reason for this is that the heat exchanger (and circulator/pump) of the boiler will be the first to suffer from any air and lack of water in the system, an installation that has radiators above the top of the boiler provides a good method of purging air and warning of low water content within the primary heating circuit.