Plumber in Greenleys
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Here is something that catches out a lot of people in 1970s Milton Keynes housing, including people who have just spent money on a new boiler: your radiators are probably the wrong size now, and the rules changed underneath you.
Greenleys is exactly the sort of estate where this comes up, so it is worth explaining properly.
Based in Two Mile Ash, around ten minutes away. Gas Safe registered, registration number 981362.
- Gas Safe registered 981362
- Around ten minutes from Two Mile Ash
- Usually some radiators need changing, not all of them
- Booked work Monday to Saturday, 8am to 8pm
Last updated
Why the right size changed
Heating systems of this era were designed to run at a flow temperature of around 75 to 80°C. Radiators were sized accordingly, and at that temperature a fairly modest radiator delivers plenty of heat.
Part L of the Building Regulations now requires new and fully replaced wet heating systems to be designed for a maximum flow temperature of 55°C. The reason is efficiency: a condensing boiler only condenses, and only reaches its rated efficiency, when the return temperature is low enough.
The consequence is direct. A radiator delivers less heat at a lower flow temperature, so it has to be larger to do the same job. A radiator correctly sized in 1976 is undersized in 2026.
Why this matters more than it sounds
This is the reason a lot of people who replaced a boiler did not get the improvement they expected.
The new boiler is capable of running efficiently. The radiators will not let it, because at 55°C they cannot deliver enough heat to warm the rooms. So the installer turns the flow temperature back up to make the house comfortable, and at that point you have a very expensive non-condensing boiler.
The house is warm and the bill is unchanged, and nobody explains why.
What to actually do about it
- Do not replace every radiator by default. A room by room heat loss calculation tells you which ones are genuinely undersized and which are fine. In most houses it is some rather than all, which costs considerably less than a wholesale replacement.
- Ask what flow temperature the quote assumes. Manufacturer output figures are usually quoted at a higher temperature than your system will run at. Asking what temperature a stated output is based on is a fair question and the answer is informative.
- Check the pipe feeding it before upsizing. On small bore or microbore legs, a larger radiator may not deliver its rated output because the pipe cannot supply the flow. Common in housing of this era.
- Get the system balanced afterwards. Changing radiators changes the balance. A job that ends without rebalancing is not finished.
See radiators and central heating installation.
The rest of the estate
Greenleys is 1970s, adjacent to Wolverton, with the profile that goes with it: third generation boilers, decades of accumulated magnetite in systems that have often never been cleaned, and gravity hot water in many properties where converting to an unvented cylinder is the biggest single improvement available.
Hard water
Same Anglian Water supply as the rest of Milton Keynes, around 300 mg/l of calcium carbonate against a UK average of 207. See our hard water guide.
Getting to Greenleys
Around ten minutes from Two Mile Ash. Close, so out of hours callouts here are practical.
Frequently asked questions
I had a new boiler and the house is no warmer. Why?
Most often radiators sized for a higher flow temperature than the new system is designed to run at. The boiler is capable, the system will not let it perform.
Do I have to replace all my radiators?
Usually not. A heat loss calculation identifies the ones that are genuinely undersized, which is normally some rather than all.
Can I just fit a bigger radiator?
Check the pipe feeding it first. On small bore or microbore, a larger radiator often cannot get the flow it needs to deliver its rated output.
What is balancing and do I need it?
Setting each radiator’s flow so heat is distributed properly. Any radiator work changes it, and a job that ends without rebalancing is incomplete.
Do you cover Fullers Slade and Hodge Lea?
Yes, along with Stacey Bushes, Wolverton, Stonebridge and Two Mile Ash.
What we do in Greenleys
Where we cover in Greenleys
- Greenleys
- Fullers Slade
- Stacey Bushes
- Hodge Lea
- Wolverton
- Stonebridge
- Two Mile Ash
Get in touch
Call 07514 312117 or send a WhatsApp. Gas Safe registered 981362, CIPHE member, fully insured.