The boiler
Pump and expansion vessel are built in, so the heating side no longer needs a tank in the loft.
System boilers · Sanderstead CR2
System boiler installation in Sanderstead
Sanderstead’s detached and larger semi-detached houses have often been extended, and 2 or more bathrooms are common. That’s where a system boiler with a cylinder earns its place. We size the new one for your home as it is now, not as it was built.
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Extended homes
Sized for the house you have now
An extension or a loft conversion adds radiators, and often a bathroom. The original boiler was sized for a smaller house, so a like-for-like replacement can leave you short of heat on cold days or of hot water on busy mornings.
We size a new system boiler to your home’s heat loss as it is today, and the cylinder to how many bathrooms you use at once. Both are confirmed on the survey, not guessed from the number of bedrooms.
For how system boilers work in general, see system boiler installation. For repairs and servicing in the area, see our Sanderstead page.
The cylinder
Keep, replace or upgrade your cylinder?
Many Sanderstead houses have a cylinder in the airing cupboard. What happens to it depends on its age and what you need from it.
| Your cylinder now | What we’d usually suggest |
|---|---|
| Recent, well insulated and heats quickly | Keep it and connect the new boiler. It saves cost and disruption |
| Old, slow to heat or poorly insulated | Replace it alongside the boiler, while the system is drained anyway |
| Vented, with weak showers upstairs | Consider an unvented cylinder for mains-pressure hot water, if your mains flow allows |
Unvented cylinders must be installed by someone with an unvented hot water qualification (G3). We’ll confirm on your quote.
How it fits together
A system boiler set-up in a family home
The cylinder
Stores hot water so several taps and showers can run at once. Usually in the airing cupboard.
The controls
Time and temperature control for heating and hot water, as Boiler Plus requires, plus a smart thermostat if you want one.
The loft
With an unvented cylinder, both loft tanks can come out. With a vented one, the cold water tank stays.
Sizing guide
What size boiler do I need?
A rough guide for Croydon homes. Bigger isn't better: an oversized boiler cycles on and off and wastes gas. We confirm the size by checking your water pressure and flow rate on the day of the survey.
| Home | Bathrooms | Usually suits | Output |
|---|---|---|---|
| Flat or 1 to 2 bed house | 1 bathroom | Combi | Around 24 to 28kW |
| 3 bed house | 1 bathroom | Combi | Around 28 to 32kW |
| 3 to 4 bed house | 1 bathroom + en-suite | Larger combi | Around 32 to 38kW, if mains flow allows |
| 4 bed or more | 2+ bathrooms used at once | System boiler + cylinder | Sized to the home’s heat loss |
Comparing quotes
What a system boiler quote should include
Use this to compare any two quotes. If one is cheaper, check it isn’t simply missing something on this list.
A proper installation includesWhy it mattersAsk on any quote
A survey of flue, gas supply and water flow
Decides the boiler size and whether a combi will give decent showers.
“How did you size the boiler?”
System cleaned to BS 7593, with inhibitor
Sludge from the old system is the main killer of new boilers.
“Is a full system clean included?”
Magnetic system filter
Keeps catching debris for the life of the boiler.
“Which filter, and where will it go?”
Controls that meet Boiler Plus
A legal requirement in England, and it saves gas.
“Which controls are included?”
New flue kit, positioned to the rules
Reusing an old flue or a bad position can fail inspection.
“Is the flue new, and where will it exit?”
Condensate pipe protected from frost
A frozen condensate pipe is the most common winter breakdown.
“Where will the condensate drain?”
Old boiler, tanks and cylinder removed
Disposal costs money. Make sure it’s not an extra on the day.
“Is removal and disposal included?”
Building Control notified, warranty registered
Without them, selling the house and claiming on the warranty get harder.
“Who notifies, and who registers the warranty?”
In Sanderstead
System boiler installation nearby
FAQ
System boiler questions from Sanderstead
Should I switch my system boiler to a combi?
In a big Sanderstead house with several bathrooms, usually not. A modern system boiler and a good cylinder will serve you better. We’ll explain the trade-off.
We’ve added an en-suite. Do we need a bigger cylinder?
Possibly. Cylinder size follows how much hot water you use at once, so another bathroom can tip it. We check on the survey and tell you if the current one will keep up.
Does an unvented cylinder need servicing?
Yes. Unvented cylinders have safety valves that need regular checks, and the manufacturer’s instructions set how often. It can be looked at when the boiler is serviced.
Do you cover Riddlesdown and the edges of Sanderstead?
Yes. If you’re not sure about your road, put your postcode in the quote form. We also cover Purley, Selsdon and South Croydon.
What size system boiler will I need?
It depends on your home’s heat loss, which an extension changes. Larger homes with 2 or more bathrooms in use at once need a system boiler and cylinder sized to the heat loss. The survey confirms the exact size.
Guides
Read before you decide
- Choosing a boilerCombi vs system vs regular boiler: which is right for your home?Combi, system or regular boiler? How each one works, which homes each suits, and when changing type makes sense. A plain guide from Gas Safe engineers.Read the guide
- Choosing a boilerWhat size boiler do I need?What size boiler do you need? How kW, mains flow rate, bathrooms and heat loss decide it, why bigger isn’t better, and the rough sizes for flats and houses.Read the guide
- Rules and paperworkBoiler warranties explainedHow boiler warranties work: registration, annual servicing, the Benchmark checklist, what can void a warranty, and the difference from an installer’s guarantee.Read the guide
Everything we do
New boilers
Conversions
Repairs & servicing
Price a system boiler in Sanderstead
Tell us about any extension or loft conversion and how many bathrooms you have.