Additives To Central Heating System To Remove Sludge/Scale

2 Jul 2010
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United Kingdom

Are there any additives that I can add to our central heating system to process sludge and scale by running the central heating for a month or so then draining it and flushing it out.

I have a 1L bottle of Sentinel X100 inhibitor but that is what is added after the system has been cleansed then refilled as far as I am aware?

Are there any other products in the Sentinel range or any other suppliers that will treat sludge and scale while the system is in operation?

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Sentinel X400. Drain some water out before adding to ensure it gets right into system, can be left for a month or so to work.
X400 directly into a radiator is the simplest way of doing it. Use a funnel to pour it in via the blank plug on top of rad after draining enough water from rad to allow X400 to be added. Follow the instructions on bottle. Don't expect miracles on a badly sludged system
Thx for the replies and the advice.

Whats the best way to drain off some liquid from the system before I inject the X400, my thoughts were as below?

1. Turn off the system and close all system radiatior inlet/outlet valves except both valves on the radiator to be injected.

2. Tie up the ball cock on the sytem header tank and drain off some fluid from the system.

3. Remove the bleed valve and inkect the X400 into the selected radiator then replace the bleed key.

4. Untie the header tank ball cock, open up all radiator valves and turn the system back on bleeding radiators where required.

Would the above procedure be OK or do I need to change anything?

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You need to remove a litre of water from the system first before you add a litre of X400. (drain a little more to give youself some extra space).
That is of course assuming that your only putting one, 1 litre bottle in.

No need to shut system down if the radiator valves are holding.
Although if the system has been on, the water will be hot, hot, HOT.

Choose a radiator.

Close off both valves. Take a note of the number of turns on the lockshield valve, you will open this up the same amount later on to keep the system balanced (assuming it is balanced in the first place and that the other valve is a TRV).

Get a container and some rags, crack open the "nut" at the radiator. This would be the one at the bottom, between the lockshield (or TRV) and the radiator. The nut should only be loosened a little, not removed completely. Get the container under the nut. Be aware the liquid will not drip straight into the container in a nice neat controller manner, it could squirt out in a variety of directions.

Drain some liquid into the container, you shouldn't need to open the bleed valve at this point, try to avoid getting the liquid onto the carpet etc.
(it could leave a stain, especially if its sludge)

You will be able to retighten the "nut" to control the flow.

Once you have removed the amount of liquid tighten the nut back up.
This may require several visit depending upon the size of container and available space.

Remove the plug from the top of the radiator and use a suitable funnel (or other arrangement) to pour in your X400.

Replace the plug.

Open up your valve(s) by the correct amount (number of turns from earlier).

Once you have it running for a while you may want to bleed the rad to remove any air.

Job Done...........Nearly !

As an alternative you could try syphoning liquid out of the top plug if you have problems at the pipework.
There may be alternative ways depending upon the layout of your system.
Check to see if there is a readily accessible system drain, this could also be used to drain out the required amount, and will be needed later.....
This method ensures all chemicals are in the system, at the right place, to do the most good, straight away.

BE AWARE........

X400 can stay in the system for up to 1 month (if memory serves), after that ALL the liquid needs to be removed, (perhaps even consider a flush arrangement?) to ensure no X400 remains in the system. That will be where a readily accessible drain valve comes in, some systems may have more than one drain point. It should be drained from them all.

Once you have done all that I would consider using the same technique to put in the X100 (and X200) into the system as the expansion tank in the loft usually has the pipe coming from the side, not the bottom, resulting in some additives staying up in the tank.

Then the refilling of the system.........woohoo.

Thank you for the detailed reply describing the method.

The X400 I have is a concentrated version in an injectable 275ml cartridge with a custom sized screw on nozzle that goes into the bleed valve opening. I presume I can use it in a sealant/mastic gun to pump it into the radiator via the bleed valve opening?

As I will be using the bleed valve opening to inject the X400 into the system, I think that I will try siphoning liquid out of the top of the radiator first and if that fails I will go for the unscrewing of the bottom nut option.

Once again, many thx for your detailed reply, it is very helpful to me and I am sure will be of benefit to others.

What about a mains flush first, then fit a magnetic filter. Then place in cleaner :]
Haven’t used the cartridge method so can’t comment – sorry.

As mentioned in previous post , it would be beneficial if you could find a way to flush out the system using continuous flow of water. This could be done before the X400 and after it to try and ensure its complete removal.

Magnetic filters can be bought via ebay for around the £75 mark sometimes. Obviously the price varies.
Retails in screwfix for £99.
Different types available, from different places.
Believe there are previous threads on here about different types.
why not just put a magnetic filter on and leave it on, then add inhibitor..

permanent protection will last a last a life time, but inhibitors do loose their effectiveness, and corrosion does restart at some point in the future...

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