19 Cockney Hill, Reading. RG30 4HF

Tel. 0118 942 4981  or  0770 231 6157






No hot water?


Scalgon are the UK’s leading experts in limescale removal. Primarily the descaling of secondary hot water heat exchangers in combination (combi) boilers, but also thermal store systems such as Gledhill mains-pressure hot water stores. We offer a premium service, second to none, and backed with 40 years experience. We have been used by British Gas, Thames Water, Reading Borough Council, Reading University, McCarthy & Stone, and very many housing-management and letting companies - and of course, very many plumbing and heating engineers use us too.

You may be experiencing poor hot water flow, or your boiler ‘cycles’ between warm and cool. Either of these two symptoms are almost certain signs that your boiler needs descaling. The flow is reduced because limescale is simply blocking the tubes, or cycling is occurring because the heat cannot be exchanged. In hard water areas combination (combi) boilers need descaling on a regular basis. Most of our work is descaling combi boilers. As combi boilers use mains water then they are prone to limescale formation. This doesn’t have to be the case at all, as you could have a CombiBuddy fitted, which would completely stop your boiler from ever having limescale build-up again. Unfortunately, most boiler owners have no such device, and even those that have been ‘protected’ have magnets or electrical devices that simply don’t work. Silicate-polyphosphate is our principle recommendation for stopping limescale in a combi boiler or similar. For whole-house protection, see LimeStop).

How to book an appointment:

Make contact with us (preferably email or text), We will allot you a date (a.m./p.m. your choice). There is a requirement to make payment before we visit - by card or bank transfer. You will be given a contract of work required before the work. The fact that you pre-pay initiates a contract that binds us to do as we have promised. So we WILL turn up (not that we’ve ever let anyone down!) and we WILL do what we say we will. We’ll be contracted to do so.


Please note that we have to park outside of the property, as our equipment is heavy. We ask you to read our terms & conditions (link below) and ensure that you know where your stop cock is, that it works, and that it does turn off the water supply to your boiler. If it turns off other homes, then that isn’t it!


So, which do you have...?

Combi boiler?


Combi boilers either have a conventional separate ‘secondary’ heat exchanger, or they have a ‘plated’ heat exchanger. It’s this part which has mains water running through it (to be heated), so it’s this part of your combi boiler that gets all ‘scaled-up’. We can easily descale it by accessing your pipe network via a water in/water out connection. This is why descaling is often better than simply replacing the heat exchanger, as we descale the outlet pipes as well. The process takes about 1-2 hours, and uses a safe acid which is recommended by boiler manufacturers. We do NOT use hydrochloric acid. We don’t usually access the drinking water part of your system, though it is sometimes necessary. But don’t be concerned as the acid we use isn’t jellified, and washes out immediately after the work. The cost is £210.00 all inclusive, though please be aware of travel charges IF you are outside of the RG postcode.


Thermal store?


Thermal store water heaters (like Gledhill products - see left) shouldn’t be confused with ‘Heat Banks’. Thermal stores heat cold mains water when it’s needed. A heat bank heats the cold water, then banks it for future use. Thermal store systems (like Gledhill products) have either a plated heat exchanger on the outside of the heater that looks like a steel brick, or it has a coil of pipe inside which is called a calorifier. This acts as a heat exchanger. This coil can get VERY scaled-up, to the point of being completely blocked. But as long as there is some flow, then we can descale it. The process takes 2-3 hours. We use a safe acid which is recommended by boiler manufacturers. We do NOT use hydrochloric acid. The cost is £370.00 all inclusive, though please be aware of travel charges outside of the RG postcode. PLEASE ensure to isolate the heating to your thermal store 36 hours prior to our visit.

We work in the RG postcode area. The costs quoted above apply throughout the RG postcode area. We are prepared to travel to:

South Oxfordshire

South Buckinghamshire

West London

West Surrey

North Hampshire

East Wiltshire

We charge a travel fee of £1 per mile ‘round trip’ for any location outside of the RG postcode area, so if the distance to your property is 36 miles, the travel charge would be £72. Check it on Google Maps. Please note that if your property is NOT in our work area then we cannot help you. Sorry, we don’t go to inner London - inside the North & South Circular Roads, or East London.


If, for any reason, we cannot carry out the work, then we will refund you payment, minus a call-out fee of £80 plus any acid used.



Yes, we carry out power flushing


Please see our power flushing page by clicking HERE See the brilliant BoilerGuard magnetic system filter HERE






We are recommended by Gledhill to descale their PulsaCoil BP thermal stores

You can read all about limescale inhibitors HERE


Limescale removal

Almost any water heating appliance can be descaled - they can be brought back to ‘as new’, there are very few exceptions. So if a heating engineer tells you that your boiler is finished because the domestic heat exchanger is blocked with limescale, then take it with a pinch of salt and call us. We’ve heard this so many times. You may be offered a new heat exchanger in exchange for your limescale-blocked one. Again, this is almost certainly not necessary, though it would be prudent to check the cost. Our charges for descaling are shown above - and often cheaper than having a new heat exchanger which could cost around £200 with labour on top! And you won’t get your pipes cleaned if you just opt for a new heat exchanger either. In some instances (fairly rarely) your pipes are all that needs to be descaled. This is usually when you’ve already had a new heat exchanger fitted and the engineer discovers that it hasn’t cured the problem of low water flow! This is (usually) a cheaper process, and works out cheaper than replacing all the pipes. We also descale very many mains-pressure hot water cylinders (thermal stores), like Gledhill PulsaCoil BPs. Unfortunately these are more expensive to descale because they really do get caked in limescale. It’s important that you don’t confuse power-flushing with descaling (even some plumbers do!).


Water hardness

Wherever you are in the country you can gauge the problem of limescale formation by taking a look in a year-old kettle. Officially, the worst location for limescale is Hartlepool with a total hardness of 490ppm. Nationally, Kent, East Anglia and the Thames Valley are the worst areas. There are considerable ‘chalk’ deposits to the north and south of the Thames River. Hence Thames drinking water has a high content of calcium. Hard water is formed when rainwater dissolves calcium and magnesium salts as it finds its way down through limestone or similar rock. Heating causes the dissolved calcium and magnesium bicarbonates to break down to form a solid carbonate (limescale). This is harmless to health but causes deposits in hot water systems and kettles. Water from rock formations, such as granite, which contain little calcium and magnesium, is naturally soft.


The hardness of water is measured as milligrams per litre of calcium carbonate, i.e. 200mg CaCO/litre. Milligrams per litre is the same as parts per million (ppm). You may also see hardness expressed as milligrams of calcium per litre - these can be converted into mg CaCO/litre by multiplying the reading by 2.5. As a general indication the soap and detergents industry classify water as follows:

Hard water contains more than 200 mg of calcium carbonate per litre

Moderately hard water contains 100 to 200 mg of calcium carbonate per litre

Soft water contains less than 100 mg of calcium carbonate per litre

Water in Reading is up to 300 CaCO/litre (or 300 parts per million (ppm) - or 21 degrees Clark) and is classed as Hard to Very Hard. You can carry out a Thames Water check HERE


Limescale Inhibitors

Much has been made about electronic so-called ‘water softeners’ in our trade press and newspaper articles and advertisements. Let us though be clear about these: they are not softeners in the traditional sense since they do not soften the water. If they indeed ‘work’ in every situation then we have yet to witness it. It would appear that flow, pressure and amount of use have a considerable impact on their effectiveness. It should be remembered that we descale heat exchangers every working day, and the vast majority of the boilers we see already have a scale inhibitor fitted. One particular electronic scale inhibitor changes the molecular structure of the limescale so that it becomes ‘sandy’. It therefore collects in the first elbow joint on the hot water system. Two of the inhibitors available that use polyphosphate dosing should, in our opinion, be taken off the market, as their action can be worse than having nothing at all! The polyphosphate (a white, powdery substance) breaks off and clogs the water inlet pipes of combination boilers. A way to completely stop limescale in a combi is by fitting a CombiBuddy

If you want to protect a thermal store or your complete home, then go for a LimeStop.



Limescale formation is very damaging, not just an inconvenience. Deposits on the inside wall of a heat exchanger will take hold rapidly once the initial layer has been laid down - due to its molecular structure. Its effects will be considerable fuel wastage (due to the fact that the limescale itself has to be heated), reduced water flow and even overheating. The latter can cause damage to the boiler. Limescale deposits of just one-sixteenth of an inch can cause a loss of efficiency of 10%. To add to this the water flow will be reduced. Indeed, a 5% reduction in diameter will cause a 23% flow drop. If you removed all the scale from the water a family of four uses in a year it would weigh 70kg - about the weight of an adult.


Our service

We employ a solution of acid and water. This is highly effective and can remove the deposits in a heavily-scaled combination boiler in under two hours. For mains-fed cylinders such as Advance and Gledhill, the amount of solution used will be many times this, and according to the severity of the limescale deposits. Our acids are not jellified and wash out immediately after the de-scaling process. Indeed, we have carried out a 2-year descaling operation of drinking-water supply pipes (in Berkshire and Hampshire) for Thames Water. We always descale the hot water pipe network - not just the boiler’s heat exchanger. This is important. Far too many engineers - rather than descale - simply replace the heat exchanger. But this does nothing for the limescale that is present within the outlet pipes!


Waters heaters (and some combination boilers) tend to raise incoming temperature by 35 degrees C. So if the water coming into the boiler is 10 degrees then the overall temperature of the water at the taps will be 45 degrees. If it were coming in at 15 degrees then the temperature would be 50 degrees at the taps. Limescale forms rapidly after 60 degrees. Many modern boilers adjust the temperature to ensure that it is always the same, no matter what the time of year (and therefore the incoming temperature). The figure of 35 degrees is usually based on a flow rate of 9 litres per minute. Obviously, if you increase the flow, then the temperature drops. If you decrease the flow then the temperature increases. This is why limescale formation can sometimes be cyclical. It will build up and reduce the flow. That decrease in flow raises the temperature of the water. The hotter water results in more limescale formation.



wp8131a2ef_0f.jpg PulsaCoil BP - How does it work?







DO NOT, under any circumstances, let your ‘engineer’ descale your PulsaCoil BP with hydrochloric acid!



You can stop limescale in your PulsaCoil BP by

having a LimeStop fitted. Click HERE












Looking for a new boiler? www.boilerbuddy.co.uk

Hot out to taps

Mains cold in

A very simplified graphic and explanation:


The Gledhill PulsaCoil BP thermal store water heater is a very simple unit - consisting of just two immersion heaters and a thermostatic mixing valve. There are no other components to go wrong. However, PulsaCoil BPs do get severely scaled-up in hard water areas.


The cold mains enters low down on the front of the unit. Inside it splits and goes up to the thermostatic mixer valve, and also onto a coil (calorifier). Here, the water in the coil (mains water) is heated by the very hot water store that surrounds it (the heat exchanges) and goes to the thermostatic mixer valve, where it is blended with cold water.


The water surrounding the coil is the water that comes from the expansion tank fitted above the PulsaCoil BP. Thus there are TWO water systems, a low pressure one; that is the water in the expansion tank and the water inside the PulsaCoil BP, plus a high-pressure one; that is the water in the coil, and out to the taps. The coil where the heat exchanges gets scaled up in hard water areas.


Click on a link above for a GUARANTEED way to stop limescale


CombiBuddy - for combi boilers


LimeStop - for thermals stores

and whole house protection



Limescale removal & prevention








From just £99.00

Plus postage



Plus postage


Looking for a water softener? Our range of ‘Deep Blue’ softeners start from as little as £514 (total - including delivery!)

Click HERE