Welcome to the website of The Power Flushing Association. The power flushing engineers listed here are heating engineers who carry out power flushing of heating systems as either their principle occupation, or are equipped to provide this service. Most central heating systems suffer from corrosion. Very often this corrosion is severe enough to create a substance often referred to as ‘sludge’ or ‘magnetite sludge’. It is deposits of corrosion principally from the heat emitters (radiators), although it can also come from the boiler itself if the heat exchanger inside is constructed of a ferrous metal. Our members can remove this sludge using a method of system washing & purging called ‘power flushing’ (also sometimes referred to as Jet Flushing or System Jetting). Below is a description of the problem, and how our members can help. Click on the ‘Find a member’ link for a member of our association within your area. Click on the ‘Contact Us’ button to send an email.

Power Flushing and magnetite sludge

Sludge causes so many problems for owners of conventional wet central heating systems. Millions of pounds are spent every year on chemicals, materials and services to rid systems of the effects of sludge - in this country alone. The principle complaint connected to sludge build-up is of poor heat, or even no heat at all. We’ve therefore put together this “frequently asked questions” section.

WHAT IS ‘SLUDGE’?

Although your radiators are probably nicely painted in a glossy white, the fact is that on the inside they are bare steel. Similarly, if you have an old-type boiler it’s highly likely to have a heat exchanger made of cast iron (whereas modern ones are usually copper, and don’t corrode). This is okay to some extent, but the majority of systems suffer from bubbles of air. When air gets in, corrosion will take place. The boiler’s heat exchanger and the radiators will quite simply start to rust. This is what ‘sludge’ is, primarily. Examined closely it often looks like the iron filings that you used to sprinkle over a magnet in sciences lessons at primary school. There may even be large particles of iron and steel. Active new corrosion will be red in colour - and turn the system water an orange colour. Only power flushing will cure this.

WHY IS THE WATER BLACK?

If you take a sample of water into a jar then it will be dark grey in colour - or even black. However, let that water settle for a few minutes and the magnetite sludge will fall to the bottom. The water will clear and the sludge will lie in the bottom of the jar as a thick, oily-looking substance. Of course, this will settle into the bottom of your system too. This is why sludge often affects the downstairs circuit first in a two-storey home. Only power flushing will be able to clear this.

IS THIS DAMAGING?

Very! The fine magnetite will enter all the valves on the system. It will cause radiator valves to stick, or fail to close. It will ‘gum-up’ thermostatic radiator valves and render them useless. It will coat the inside of the Diverter valve (the valve that decides whether your system water goes to heating or hot water) in a gooey mess that will stop it working correctly. It will also attack your circulating pump - eventually causing its failure. Unfortunately, this is often ignored by plumbers. The pump is usually the first to succumb to the effects of sludge and come to a grinding halt. However, often the homeowner calls in a plumber who simply replaces the pump, but says little or nothing about the cause. It should be an alarm call as to what’s going on in the system and he should inform you that your system needs power flushing.

THE BOILER IS NOISY

Well it would be! All that sludge will get baked-on over the years onto the walls of the heat exchanger. It will build up, and slow the water from leaving the boiler. The boiler will therefore overheat - and thus become noisy. Both limescale and sludge are good insulators of heat, so it will also cost you much more in fuel. That sludge has to be heated too. Power flush it out!

COULD I HAVE LIMESCALE AS WELL?

Possible, but unlikely. Limescale forms in hard water areas only - obviously. Systems will get an initial ‘dump’ of calcium on first fill of water. However, the average system would get about thirty grams. Pretty much nothing really, although even that can cause a boiler to ‘wheeze’ as it’s usually concentrated at the boiler itself. Your system heats the water and sends it out to the radiators. That water comes back and is re-heated. It’s the same water. We get limescale in kettles because the water is obviously constantly changing, but system water is the same water - just re-heated, so there shouldn’t be any fresh water with fresh calcium. BUT, if a system leaks water (or a sealed system is very often re-pressurized) then this IS fresh water. Limescale will form - and form rapidly. Don’t worry too much about removing radiators to decorate. As long as you don’t redecorate every room every few months then it should be okay.

WHAT CAUSES AIR TO GET INTO THE SYSTEM?

Air can get in when water gets out. Leaks of water from joints or even pin holes in radiators will cause air to get into the system. But there are other factors. ‘Open’ systems (the type with a small tank - usually in the loft) will have a pipe called an Open Vent looped over into the water tank. This pipe must extend for some distance before looping over the tank. If it doesn’t then it can dribble water out when the system gets warm. This will oxygenate the system water (the water actually sucks air in) in much the same way as a garden pond is oxygenated by a fountain or water fall. On a pond, it’s a good thing; on a heating system it’s disastrous! Water simply laying in the tank will also absorb oxygen - it gets saturated with oxygen. If a system has not been designed or installed correctly then the Open Vent pipe can actually eject water into the tank when the pump is running (‘pumping-over’). This can cause a brand new system to ‘sludge-up’ in a matter of months! However, it’s cyclical. Sludge can actually cause the system to ‘pump over’ in this way also.

WHAT ELSE CAN CAUSE SLUDGE?

When a system is first installed there are naturally some chemicals present. If the system is in soldered copper joints then there can be soldering flux. This MUST be flushed out when the system is first filled with water. Not only that, but the system must be adequately flushed using a light cleansing chemical. All too often this is not the case at all. These chemicals will react and actually cause corrosion to start. Similarly, if a system is power flushed with an acid then great care must be taken to ensure it is adequately flushed from the system - otherwise it can actually cause sludge to return faster than before! This is because residues of acid will add to the corrosion process.

BUT CAN’T SOMETHING BE DONE TO INHIBIT CORROSION?

Yes! An ‘inhibitor’ should have been added when the system was first filled. This costs no more than £30 but is often left out! Only a power flush can help it now!

SO WHAT CAN BE DONE NOW?

Some method of power flushing out the sludge has to be employed. There are cleansers that must be added to the system. Some are acidic, and some are pH neutral. It should be noted, however, that with some boilers it is better to scrap the old one for a modern fuel-efficient type. BUT, a power flush will still have to be carried out prior to fitting of the new boiler.

WHAT IS A ‘POWER FLUSH’?

This is rather contentious. However, we define it here as a ‘washing & purging’ method - but each manufacturer of chemicals and flushing pumps seem to have their own description. One particular method is to employ the use of the pump within the system to distribute a chemical added. After the bonding agent has had time to cause an effect then the system will have to be purged - of both the chemical and the suspended sludge. A ‘one-hit’ power flush can also be carried out. This is where a chemical is added and pumped around the system by a power flushing pump. This sometimes requires the use of a strong chemical - to act quickly. ‘Purging’ is the essential part of power flushing. Initially, the entire system will be purged with fresh water, then individual radiator ’loops’ will be purged by shutting off all the radiators on the system bar the one being purged. The heating part of the hot water system is flushed in the same manner - as is the boiler, although usually the boiler is incorporated into the purging method. Purging can also be reversed, so that the water flow can be injected from the alternative end of the radiators. All residues of the chemical will be removed by correct purging. The complete process takes an average of eight hours in total for an average nine-radiator system.

HOW MUCH DOES THIS COST?

Power flushing charges vary according to the size of the system and the severity of the problems. The average seems to be between £300 and £550, but ask for a free quotation from engineers in your area. However, you should ask your engineer if you do indeed require a power flush. You may not.

ARE THERE OTHER COSTS?

We strongly recommend that you have an inhibitor put into the system after the power flush has been carried out. This should cost little more than £30.00 We also recommend that you have a magnetic separator installed. The MagnaMate costs just £59.00.

ANY DOWNSIDE TO POWER FLUSHING?

In order to properly power flush a system the engineer will need to be able to isolate radiators. This means that radiator valves must be functioning. That is, it must be possible to shut the valve down. Some older valves may be too worn, and may need to be replaced either prior to the power flush, or at that time. However, to properly balance a system it is often necessary to do be able to regulate the flow through a radiator by shutting down one of the two valves - so replacement is sometimes necessary anyway. If a valve hasn’t been adjusted for some time then movement during the power flush can result in that valve passing water at the gland. However, your power flushing engineer will be well aware of this. Unfortunately, there’s lots of ‘pub talk’ about power flushing, and sometimes stories get ‘glazed’ by untruths and misconceptions - even from plumbers! Systems are never “held together by rust” as such, although they may be weak. However, it is surely better that a system leaks during an attempted salvation than leaks at midnight on Christmas Eve! It is true that acid-based chemicals are naturally more aggressive at tackling magnetite sludge. However, if your engineer has opted to use an acid then he may have of done so because he feels that there’s ‘nothing to lose’ by such a method. In other words, if nothing is done then obviously the system would have to be replaced - so better to try an aggressive method, but it could result in saving the system. Above everything, talk to your engineer about your system. Ask him if a power flush is absolutely necessary, and what you can expect afterward. What you must understand above all else is that power flushing will not clear a complete blockage in your heating system UNLESS certain action is taken by the engineer to clear the blockage prior to the actual washing & purging stages. It is probably not economic to have your system power flushed just to ‘save’ you money on your heating bill. It is primarily done for better heat output and perhaps noise nuisance.

Installation of a new boiler.

Just about the best time to power flush your heating is when you are having a new boiler installed. All boiler manufacturers now insist that a power flush cleanse is carried out prior to fitting a new boiler - and it can invalidate the guarantee if it is not done. Your boiler-fitting engineer can liase with a power flushing engineer to carry out the power flush in the time between your old boiler being removed and the new boiler being fitted.

If constant venting is a nuisance (perhaps in a radiator fitted in a loft conversion) then an automatic air vent can be fitted in the top of the radiator. This is only the size of the normal vent and totally unobtrusive. However, it should be noted that air-creation acts as a warning that something is wrong with your system. If the air is expelled naturally then you will have no knowledge of this fault.