Sludge flake (picture) is a condition where the sludge in the system has hardened into flakes of various sizes. These flakes are much larger and more rigid than normal sludge, which is mud-like. Once the sludge flake has started forming in the system, it becomes very easy to cause problems in the boiler, pump, pipes and radiators. Sludge flake is currently the number 1 reason, why you central heating problems arise.

How common / big a problem is sludge flake at the moment?
Over 70% of properties that have problems because of sludge is because of sludge flakes. A system can operate fine with a lot of sludge in it, because it is soft and can be pushed “out of the way” by the pump. Sludge flakes on the other hand, has large pieces and it takes very little of them to block up a pumps, radiator valves or heat exchangers. They also get stuck and tend not to move around, even when power flushed. It is easy for sludge flakes to break parts, because they are large enough to block things up and rigid enough to resist parts from operating properly.

Symptoms of sludge flake/s in a central heating system:
- System shuts down or starts experiencing problems regularly (say yearly) even though the system has been power flushed/cleaned. Example: boiler breaks down yearly.
- System water is completely clear, like tap water, even though it has not been cleaned or power flushed before.
- Radiator/s stop working one by one, until sections of the central heating system stops working all together. Radiators can become intermittent; works well then stops for some days, then start working again by themselves. In the beginning of this process; the first radiator stops working then starts working again, slowly getting worse until it stops altogether.
- Newly build properties experiencing problems with their central heating or boiler (new would be under 7 years old)
- When a power flush is performed, the water is completely clear. A lot of engineers are not aware of sludge flake so they will miss the sign, that the clear water can actually indicate big problems. It is also easy not to see the flakes because a standard power flush tends NOT to get all of them out of the system.
- Continuous pump changes; pump works fine then stops again. Change for new pump, same thing happens within months.
- Newly added radiators, to the system, works when installed, but then become unreliable within weeks.
- Clinging sounds in the radiator/s when the central heating is on. This is the rigid flakes being disturbed by the pump.

How does it look like? Click for picture

Is a "standard power flush" effective in removing sludge flake from the system?
Not really, the flakes are large and resist being moved around the system and hard to get out. The procedures that need to be done are very different from a standard power flush, most power flush companies and gas engineers don’t know how to deal with them or even know that this condition exist. It is a lot more work to get rid of sludge flake and most companies will not work on it. We have specialist members, in our association, that would clean systems with sludge flake. If you know you have this condition, tell the power flush company in advance, it saves a lot of time and money if they know from the start. If you are not sure or have more questions, please contact us.

How to test for sludge flake:
The test and results are counter intuitive to normal sludge. Take two, central heating water samples of at least 100ml. Discard the first sample and use the second one.

- Positive test results:
If the water is completely clear, even if the system has not been cleaned = sludge flake
Actual flakes in the bottom of the sample container = sludge flake

- Negative results:
It is rare to have a very dark water sample and sludge flake, as the process of making it converts the sludge in suspension (dark water) into sludge flakes, diminishing the sludge in suspension, with the water quality becoming clearer and clearer until water is completely clear. In the start of sludge flake forming, there are rarely enough flakes in the system to stop anything from working completely. So the build-up tends to go unnoticed.

External signs of possible sludge flake build-up in the system:
Skirting board radiators (normally in the kitchen), plastic pipe runs, rubber pipe or piping.

What are the odds with sludge flake in the system that standard power flushing will fix it?
- Unblocking a boiler that does not work because of sludge flake in primary heat exchanger= 40%
What increases your odds? Have a specialist member flush the system first, then change heat exchanger for a new one.
- Unblocking the hot water heat exchanger with sludge flake in it = 20%
What increases your odds? Have a specialist member flush the system first, then change heat exchanger for new one or remove and flush it out separately.
- Unblocking a radiator/s that does not work at all = 30%
What increases your odds? Using one of our specialist members to unblock the radiator/s first, then flush the system.
- Unblocking a partially blocked radiator = 50%
What increases your odds?  Use a specialist member to unblock the radiator first, then flush the system.
- Cleaning a system well enough so that it doesn’t play up in any way for the next 2 years = 50%
What increases your odds? Use a specialist member that work on sludge flake all the time.

Contact us regarding sludge flake here