Immersion Heater Installation and Repair in Milton Keynes
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An immersion heater is the simplest thing in a hot water system and the one most likely to fail in a very hard water area. It is an electric element sitting in your hot water cylinder, heating the water directly, and it does that job reliably until scale builds up on it and destroys it.
In Milton Keynes, that happens faster than most places. The water here averages around 300 mg/l of calcium carbonate through Anglian Water, with MK8 at roughly 317 against a UK average of 207. Scale forms on any hot surface, and an immersion element is nothing but hot surface.
We install, repair and replace immersion heaters across Milton Keynes and the surrounding towns, in homes, rental properties and commercial premises. Gas Safe registered, registration number 981362, and we handle the electrical side of this work in house.
- Gas Safe registered 981362
- Fixed price agreed before we start
- Milton Keynes and 20 miles around
- 8am – 8pm, Mon to Sat
Last updated
What it is and when it gets used
As a backup.
The most common role. Your boiler heats the cylinder normally, and the immersion is there for when the boiler fails, during a service, or over summer if you turn the heating off entirely.
As the primary heat source.
In properties with no gas, or where the cylinder is heated electrically by design.
On an off-peak tariff.
Where a cylinder is heated overnight on cheaper electricity and the stored hot water lasts the day. Some cylinders have two elements for this, a lower one for the overnight bulk heat and an upper one for a quicker top-up during the day.
The backup role is the one worth thinking about. An immersion you never use is an immersion you find out has failed on the morning the boiler dies, which is the least convenient possible moment. Running it briefly once or twice a year confirms it still works.
What goes wrong
The element fails, and scale is usually why
Scale builds on the element as an insulating layer. The element continues producing the same heat, but that heat can no longer transfer into the water efficiently, so the element runs hotter and hotter under its own crust until it fails.
Symptoms: no hot water from the immersion, the circuit tripping, or water that heats far more slowly than it used to.
In a very hard water area this is the normal failure mode, and it is why immersion elements do not last as long here as the manufacturer’s typical figures suggest.
The thermostat fails
Each element has a thermostat controlling the water temperature and a thermal cut-out as a safety backstop. A failed thermostat produces either no heating at all, or water far hotter than it should be. A tripped cut-out usually means the thermostat has already failed.
Water coming out scalding hot from a cylinder is not something to live with. It is a thermostat problem and it is a scalding risk.
The circuit trips
An element that has failed and allowed water into the electrical side will trip the protective device. That is the protection doing exactly its job. Repeatedly resetting it rather than finding out why is the wrong response.
It heats slowly, or not enough
Usually scale, either on the element or in the cylinder generally. Occasionally an element that has been replaced with one of the wrong length for the cylinder, so it is heating only the top portion.
Element choice matters here
Not all immersion elements are the same, and in this water the difference is worth paying for.
Copper elements
are the cheaper standard and they scale readily.
Incoloy elements
are made from a nickel-iron-chromium alloy that resists scaling and corrosion considerably better. In a hard water area they last meaningfully longer and the price difference is small relative to the labour of changing one.
In Milton Keynes we would fit Incoloy as the default. If you are getting quotes, it is worth asking which is being supplied, because the cheaper quote is sometimes just the cheaper element.
Replacing an immersion heater: what is involved
More work than people expect, and it is worth knowing why:
- 1
Electrical supply isolated and the immersion disconnected
- 2
Water supply to the cylinder isolated and the cylinder drained down, which is the part that takes time
- 3
Old element removed. This is where jobs go long, because a seized element in a cylinder that has been in place fifteen years does not always want to move, and forcing it risks damaging the cylinder boss
- 4
New element fitted with a new gasket, thermostat set to a safe temperature
- 5
Cylinder refilled, air purged, checked for leaks around the boss
- 6
Electrical connection remade and tested
The seized element is the honest variable. Most come out. Occasionally one does not, and on an old cylinder that is already past its useful life, replacing the cylinder is the better answer. We tell you if we think that is where things are heading rather than discovering it halfway through.
Immersion heaters in Milton Keynes: the local picture
1980s and 1990s estates, Furzton, Emerson Valley, Shenley Brook End and Loughton. Vented cylinders in airing cupboards with original immersion heaters, many of which have never been changed. These are the properties where the backup immersion is most likely to be quietly dead.
1970s estates, Beanhill, Coffee Hall, Netherfield, Fishermead and Conniburrow. Similar, and often with electrical supplies that were adequate when installed and worth checking now.
Newer estates, Brooklands, Whitehouse, Fairfields, Oakgrove, Tattenhoe Park and Glebe Farm. Usually unvented cylinders, which also carry immersion heaters. The element fails the same way, and access can be tighter.
Older property in Stony Stratford, Newport Pagnell, Olney and Wolverton. Frequently the properties where the immersion is a genuine primary or seasonal heat source rather than a backup.
Getting more life out of it
- Test the immersion once or twice a year even if you never use it, so you know it works before you need it
- Do not run it at maximum temperature. Scale forms faster the hotter it gets, though the setting must stay high enough to control legionella in a stored system, so this is a setting for your engineer rather than a dial to turn down yourself
- Fit an Incoloy element rather than copper
- Consider a water softener if scale is causing problems throughout the property. Our hard water guide covers the wider picture
- If the circuit trips, do not keep resetting it. Find out why
- Insulate the cylinder properly, since it reduces how often the element runs at all
Frequently asked questions
How long should an immersion heater last?
Manufacturer figures assume average water hardness. In Milton Keynes, at around 300 mg/l, expect less. Incoloy elements last considerably longer here than copper.
My immersion trips the electrics. What does that mean?
Usually a failed element allowing water to reach the electrical side. The protective device is doing its job. It needs replacing rather than resetting.
The water is scalding hot. Is that dangerous?
Yes, it is a scalding risk and it points to a failed thermostat. Worth dealing with promptly, particularly in a household with children or elderly residents.
Can you replace the element without replacing the cylinder?
Almost always. The exception is an old cylinder where the element is seized solid and removing it risks damage. We will tell you if that is where we are heading.
How long does a replacement take?
Allow a couple of hours, most of which is draining and refilling the cylinder. Longer if the old element is seized.
Do you do the electrical connection too?
Yes, we handle that side in house rather than bringing in a second trade.
Should I use the immersion instead of the boiler?
Generally not, since electricity is usually the more expensive way to heat water. The exception is an off-peak tariff, where overnight heating can make sense.
Do you replace immersions in rental properties?
Yes, and testing the backup immersion during a void period is worth adding to the between-tenancies list.
You may also need
Book a replacement
Call 07514 312117 or send a WhatsApp with a photo of your cylinder and the immersion cover. Gas Safe registered 981362, CIPHE member, fully insured.