Stevenage’s heating systems are some of the most sludge-prone we work on anywhere in Hertfordshire – and there’s a specific reason for that. A lot of the original New Town housing was fitted with microbore pipework in the 1960s and 70s, and microbore (typically 8mm or 10mm internal diameter) is far more prone to flow restriction from magnetite sludge than standard 15mm or 22mm pipe. Combine that with sixty years of corroding steel radiators and the hard chalk-aquifer water that comes through the mains, and you’ve got a recipe for the cold-spot radiators, kettling boilers and rocketing gas bills that we see week in, week out across Bedwell, Shephall, Chells and Pin Green.
Professional dual-magnet power flushing machine, magnetic filter fitted, inhibitor added on completion.
Three factors stack against the average Letchworth heating system. First, sheer age – most properties in central Letchworth are 80+ years old and many original heating pipework runs are 40–50 years old. Second, the Affinity Water hardness (around 300–370 mg/l calcium carbonate) accelerates internal corrosion of steel radiators. Third, the bigger Garden City detached homes often have 12 or 14 radiators on a single system, meaning sludge has more places to accumulate and the heating struggles to circulate properly once buildup starts.
Skipping a flush before fitting a new boiler is the single fastest way to kill a new heat exchanger. Most manufacturer warranties (Worcester, Vaillant, Ideal) become void if the system isn’t properly cleaned at install.
Particularly cold at the bottom while the top is warm – classic sludge buildup stopping water circulation. The bigger old cast iron and pressed steel radiators in early Garden City houses are particularly prone to this.
Sounds like a kettle boiling. Caused by sludge restricting flow through the heat exchanger. Usually means the boiler is working much harder than it should – and often not for much longer.
Should be reasonably clear. If it’s black, brown or rust-coloured, you’ve got significant magnetite circulating.
Sludge insulates radiators from the inside. If your Garden City house used to warm up in 45 minutes and now takes 90, the system is fighting the buildup.
The boiler runs longer to deliver the same heat. Letchworth customers regularly see 15–20% reductions in winter gas usage after a thorough flush.
We check the system water condition, pipework size, system pressure and overall condition. If the water comes out the colour of strong tea, you definitely need a flush.
Our power flushing machine connects to the boiler tails and circulates a specialist cleaning solution at high velocity. Dual magnets capture magnetite as it's dislodged.
Every radiator is agitated individually - physically tapped and reversed in flow direction to dislodge stubborn sludge. Important for the larger old cast iron radiators in Garden City homes, which trap more sludge than modern panel radiators.
On completion we fit a magnetic filter (Adey MagnaClean Pro2 or similar) on the return pipe, then add a corrosion inhibitor to protect the system long-term.
Standard 8–10 radiator system: 4–8 hours, usually a full day. Larger Garden City systems with 12+ radiators or microbore sections: 6–10 hours.
A typical Letchworth power flush on an 8–10 radiator system runs £450–£650 including magnetic filter and inhibitor. Larger Garden City systems with 12+ radiators run £700–£1,000. Always quoted upfront, never variable mid-job.
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If radiators are cold at the bottom, the boiler makes strange noises, water comes out black when you bleed a radiator, or the system has never been flushed in 10+ years – you almost certainly need one. Particularly likely if you’re in a Garden City property with original 1970s or 80s radiators still installed. Send us a couple of photos and we’ll give you a clear answer.
Sometimes – if the system is newer than 10 years or has been recently cleaned. But for most of Letchworth’s older Garden City systems, only a power flush actually shifts the sludge properly. We’ll tell you honestly which you need.
Cast iron is generally robust and handles flushing well. Older pressed steel radiators with existing weak spots can occasionally develop pinhole leaks during a flush – but those radiators were close to failure regardless. We always warn you upfront if a radiator looks suspect.
Yes, but it takes longer and needs more careful handling than standard pipework. Microbore traps localised sludge more easily, so radiator agitation is essential. We do these regularly across the post-war Letchworth estates.
On a heavily sludged Letchworth system, customers typically see 15–25% faster heat-up times and 10–20% lower winter gas bills. Cold-at-the-bottom radiators usually warm fully across after a proper flush.
Almost always, yes – and most manufacturer warranties require it. Fitting a new boiler onto a sludged system is the fastest way to destroy a brand-new heat exchanger. We provide a chemical analysis report for warranty registration.
Fixed-price quote, magnetic filter and inhibitor included, 12-month labour guarantee.