How many showers at once?
The single biggest factor. If 2 often run together, stored hot water usually wins.
Back boilers · Purley CR8
Back boiler replacement in Purley
Purley’s 1920s and 1930s houses are mostly larger family homes, many with 2 or 3 bathrooms. So if you’re replacing a back boiler here, a combi isn’t the automatic answer. We look at how much hot water you use and recommend the boiler that fits.
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Bigger houses
Replacing a back boiler in a larger home
A back boiler heats a cylinder of stored hot water, fed from a tank in the loft. In a smaller house the usual move is to a combi and lose the lot. In a Purley house with several bathrooms, losing stored hot water can be a step backwards: a combi serves one outlet well at a time, and 2 showers at once is where it struggles.
So the first question isn’t where the new boiler goes, it’s how your household uses hot water. Then we look at your mains flow, the space you have for a cylinder and where a flue can go.
For the job in general, see back boiler replacement. For everything else in CR8, see our Purley area page.
Your options
Three ways to replace a back boiler
| Replace with | Suits | What changes |
|---|---|---|
| A combi | One bathroom, or 2 rarely used at once, with good mains flow | Cylinder and both loft tanks out. Hot water straight from the mains |
| A system boiler and cylinder | 2 or more bathrooms in use together | Heating tank out. With an unvented cylinder, the cold tank goes too and showers run at mains pressure |
| A regular boiler, keeping the tanks | Homes where mains flow is too weak for mains-pressure hot water | Least change to the loft and cylinder. Showers may need a pump |
The survey confirms which option works in your house.
What decides it
Four questions we’ll ask
How strong is your mains?
A combi and an unvented cylinder both depend on it. We measure pressure and flow on the survey.
Where can a cylinder go?
The existing airing cupboard usually works. A new unvented cylinder needs a route for its discharge pipe too.
Where can the flue go?
The new boiler doesn’t use the old chimney the way the back boiler did. It needs its own flue through a wall or the roof.
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 |
Who you’re dealing with
Don’t take our word for it. Check us.
Anyone working on gas in your home must be on the Gas Safe Register. It takes thirty seconds to check, and you should check whoever you use.
- 1Go to the Gas Safe Register’s “Find an engineer” page.
- 2Enter our registration number, 567789.
- 3On the day, ask to see the engineer’s Gas Safe ID card. The back lists the work they’re qualified to do.
Gas Safe registered
Registration number 567789. Required by law for anyone working on gas appliances.
City & Guilds certified
Formally trained and qualified in plumbing and heating.
Fully insured
Public liability cover for work in your home.
On Track Plumbing & Heating Ltd
A registered limited company, not a one-off trader. Your quote and paperwork come from the company.
Back boiler replacement nearby
FAQ
Back boiler questions from Purley
Is a combi right for a big Purley house?
It depends on bathrooms more than bedrooms. With 2 or more showers used at once, a system boiler and cylinder usually serves better. We’ll check your water flow and recommend honestly.
Can I keep my cylinder?
Sometimes, if it’s in good condition and suits the new boiler. Many cylinders on back boiler systems are old and slow to heat, so replacing it at the same time often makes sense. We’ll tell you which on the survey.
How long does the job take?
Usually 2 to 3 days for a back boiler replacement, as the old system comes out and the new boiler goes in a different room. A new cylinder can add time. Your quote will say.
Do you cover all of Purley?
Yes, all of CR8 including Purley town centre, Foxley, Russell Hill and Kenley. We also cover Coulsdon and Sanderstead next door.
What about parking?
Hills and driveways make parking easy at most Purley houses. Around the town centre, allow for pay-and-display, and tell us in the quote form.
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 is a back boiler?What a back boiler is, how to tell if you have one, why they were fitted in 1930s and post-war homes, and what replacing one with a modern boiler involves.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
Everything we do
New boilers
Conversions
Repairs & servicing
Price your Purley back boiler replacement
Tell us how many bathrooms you have and add a photo of the fireplace. We’ll recommend the right type.