The Bhatti household — 5 adults, 4-bed detached in the BB5 postcode of Accrington — had lived with an ageing Potterton floor-standing regular boiler and a copper vented cylinder in the airing cupboard for 18 years. When the cylinder's immersion element blew and started leaking in April 2026, they finally called us for the full system upgrade they'd been putting off for a decade.
The property
1970s 4-bed detached off Whalley Road, BB5. Two bathrooms plus an en-suite (added in a 2015 loft conversion), 11 radiators, a downstairs cloakroom, and a busy family that all needed showers between 6:30 and 8am on weekdays. Cold-water mains was healthy at 3.4 bar. Water hardness in BB5 sits at around 235 ppm — moderate-to-hard.
Why a combi was the wrong answer
Two cheaper quotes had specified a large combi (40 kW+). It would have technically worked as a like-for-like replacement, but a combi can only serve one hot-water outlet at full flow. With three simultaneous showers routinely running, the temperature would drop off the third the moment the second turned on. For this household, only a system boiler + large unvented cylinder made sense.
The fixed-price quote
We specified a Baxi 800 System 2 30 kW paired with a 250L Megaflo Eco unvented cylinder. Total fixed price: £4,450, including the boiler, cylinder, full G3 kit (expansion vessel, T&P valve, tundish, D1/D2 discharge routed to outside), MagnaClean filter, chemical hot flush across all 11 rads, Fernox F1 inhibitor, and a wired-thermostat 2-zone setup (upstairs / downstairs). Baxi 10-year manufacturer warranty registered.
The install (3 days)
- Day 1: Full drain-down. Removed the Potterton floor-standing boiler and its 22 mm feed / return. Removed the old copper cylinder and cold-water storage tank in the loft (the Bhattis got their loft floor space back — a hidden win).
- Day 2: Fitted the Baxi 800 System in the utility (wall-hung, freeing floor space). Fitted the 250L Megaflo in the airing cupboard with full G3 kit. Ran new 28 mm cold main to the Megaflo, T&P discharge externally to a tundish, D2 pipework to outside.
- Day 3: Chemical flush + F1 dose. Wired the 2-zone motorised valves. Commissioned to Baxi spec, recorded flue-gas analysis, filled Benchmark. G3 certificate issued and Building Control notified via Gas Safe.
The morning-after result
Three simultaneous showers, all running full-hot at high mains pressure. The Bhattis' gas usage in month one dropped 22% vs the same month a year earlier (measured on their smart meter) — mostly because they now have separate upstairs / downstairs zones and aren't heating empty bedrooms while everyone's in the lounge.
Why Accrington homes suit this spec
BB5 has a lot of 1960s-70s 4-bed detached stock, most fitted originally with a regular boiler + vented cylinder. Converting to an unvented system + modern condensing boiler frees loft space, gives mains-pressure showers to every bathroom, and reclaims the airing cupboard. If you're on Whalley Road, Baxenden, Church, Oswaldtwistle or the Baxenden estates — this is the upgrade path that pays back over 15 years, not 15 months.
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