Project Overview
Plumb London replaced an ageing Potterton boiler with a new Vaillant ecoFIT Pure system boiler at a private home in Wimbledon, SW19. The original appliance was more than twenty years old and, although it still produced hot water, had begun calling for heat when none was required — an early sign of failing controls and declining reliability. Following a full survey, the homeowner chose a complete heating system upgrade rather than further repairs. The finished installation delivers dependable, responsive heating, modern controls, enhanced system protection and a ten-year manufacturer’s warranty.

The Client’s Brief
The homeowner’s priority was restoring predictable, reliable heating without committing further money to a boiler nearing the end of its working life. Alongside performance, the client asked that disruption to the property be kept to a minimum — in particular, that an existing rear step and the tiled flooring above the under-floor void remain undisturbed. The brief, in short, was a long-term, low-maintenance heating system installed with care for the fabric of the home.
Our Survey & Recommendations
On survey, our engineer confirmed the Potterton boiler was over twenty years old and no longer economical to maintain or repair. The system firing when heat was not being called for indicated failing controls rather than an isolated fault, and we advised that continued spending on an appliance of this age would not represent sound value. We recommended a full replacement: a modern Vaillant system boiler, a complete heating controls upgrade and a system flush to protect the new equipment. The survey also identified an access constraint beneath the property — tiled flooring and the client’s wish to retain the rear step — which would govern how the new condensate waste could be routed.
Planning & Preparation
Having reviewed the survey findings, the client weighed repair against replacement and concluded that further investment in a twenty-year-old boiler was not justified. The decision to proceed with a full upgrade was taken on that basis, with the scope and equipment agreed in advance so the works could be carried out in a single, well-planned visit.
The Work We Carried Out
- Removal and decommissioning of the existing Potterton boilerv
- Full system flush using MagnaCleanse, carried out in line with BS 7593
- Installation of a Vaillant ecoFIT Pure 625 system boiler
- New horizontal flue
- Installation of a Vaillant Advance boiler protection filter
- Replacement of two 22mm motorised zone valves
- Upgrade of heating controls, including programmer, room thermostat and cylinder thermostat
- New external condensate waste arrangement, routed to suit the property’s access constraints
- Commissioning, Benchmark certification and Gas Safe registration
A very good service from start to finish. Reasonably priced, good dealings. I can recommend.
Timeline & Completion
The installation was carried out by our engineers, Bally and Charlie, and was completed and fully commissioned on 15 June 2026, with the system handed over to the homeowner the same day. The works were delivered to the agreed scope, including all certification and Gas Safe registration.
Challenges & How We Solved Them
Restricted access beneath the property. The condensate waste could not follow a conventional route because of the tiled flooring and the client’s request to keep the rear step in place. Rather than disturb either, our engineers designed an alternative external condensate arrangement that met the new boiler’s requirements while leaving the property’s existing features untouched.
Adapting existing pipework and controls. Integrating a modern Vaillant system boiler with the home’s established pipework and zoning required careful adaptation. We replaced the two motorised zone valves and upgraded the full set of heating controls, ensuring the new boiler operated efficiently across the existing circuits and responded only when heat was genuinely required — directly resolving the original fault.
The Finished Result
The home now runs on a fully modernised Vaillant heating system. Heating responds reliably and only when called for, resolving the erratic behaviour of the old boiler. Upgraded controls — programmer, room thermostat and cylinder thermostat — give the homeowner finer control over comfort and running costs, while the system flush and Advance protection filter safeguard the new equipment and extend its working life. Registration and Benchmark certification secure a ten-year manufacturer’s warranty — available because Plumb London is a Vaillant Advance accredited installer — and the alternative condensate routing means the upgrade was achieved without altering the rear step or tiled flooring.
Project Investment
The complete heating system upgrade was delivered for a fixed price of £4,740 including VAT. For a twenty-year-old system, this represented a sound investment: a new, efficient Vaillant boiler, a full controls upgrade and proper system protection, all backed by a ten-year manufacturer’s warranty — replacing recurring repair costs and the uncertainty of an ageing appliance with long-term reliability.
Why Choose Plumb London
- Specialist expertise across plumbing, heating and refurbishment. Every project is surveyed, specified and commissioned by experienced engineers, with Gas Safe registration and Benchmark certification as standard on relevant work.
- Accredited installers. As a Vaillant Advance accredited installer and a Gas Safe registered company, our work meets manufacturer and regulatory standards — and qualifies your installation for extended manufacturer warranties.
- Quality that lasts. We install trusted manufacturer equipment, protect it properly — system flushing, filtration and correct commissioning — and register warranties so you are covered for the long term.
- Respect for your home. Where access, layout or original features are a concern, we find a solution that protects the property rather than the quickest route for us.
- Clear and accountable. Agreed scope, fixed pricing and a clean, planned handover — the same standard on every job, large or small.
- Trusted across London’s residential properties, with much of our work coming from repeat clients and referrals.
Frequently Asked Questions
How do I know whether to repair or replace an old boiler?
As a rule, once a boiler is beyond around fifteen years old, repairs become harder to justify — parts are scarcer, efficiency is lower, and faults tend to recur. A survey will weigh the likely cost of keeping the existing boiler running against a replacement, so the decision is based on value rather than guesswork.
Why is a system flush needed when fitting a new boiler?
A system flush, carried out to BS 7593, removes sludge and debris that build up in older heating systems. Fitting a new boiler onto a dirty system risks blockages, noise and reduced efficiency, and can affect warranty cover. Flushing protects the new equipment from the outset.
Does a new Vaillant boiler come with a warranty?
Yes. When a Vaillant boiler is installed by a registered engineer and the installation is correctly commissioned and registered, it qualifies for an extended manufacturer’s warranty — ten years in this case — provided the system is serviced annually.
What does a heating controls upgrade actually improve?
Modern controls — a programmer, room thermostat and cylinder thermostat — let the system heat the home and hot water only when needed, and only to the temperature you want. This improves comfort and reduces wasted energy compared with older or failing controls.









