Project Overview
Plumb London was engaged to rectify a defective air-conditioning installation at a residential property in Battersea, SW11, in the London Borough of Wandsworth. A Toshiba multi-split system — fitted around nine months earlier by a third-party contractor — had developed an active water leak from one of its wall-mounted indoor units. On investigation, the root cause was an incorrectly positioned core hole, which left the condensate pipe running without the gravity fall needed to drain to the exterior. We carried out a full decommission, repositioned the pipework correctly, and completely recommissioned the system, restoring it to safe, reliable, leak-free operation in a single day.
The Client’s Brief
The client’s immediate concern was the active water leak from the indoor unit, which had caused visible damage and considerable inconvenience. Having already pursued the original installer without a satisfactory resolution, they needed a competent, trustworthy contractor to identify the fault definitively and resolve it with minimal disruption.
Their key requirements were:
- Permanent identification and resolution of the condensate leak
- Safe handling of refrigerant in line with F-Gas regulations
- Full recommissioning with confirmed system performance
- A clean, professional finish with no unnecessary damage to internal or external fabric
- Coordinated access across the ground floor, lower floors and rear garden
Our Survey & Recommendations
A site survey was carried out before any works began, inspecting the wall-mounted indoor unit and the associated condensate pipework. Our findings:
- The core hole drilled through the external wall sat too high, creating an insufficient — effectively negative — fall on the condensate pipe.
- Without adequate fall, condensate produced in normal operation could not drain freely outside, instead tracking back into the unit and leaking internally.
- The refrigerant system and the indoor unit itself were working correctly; the fault was isolated entirely to the condensate drainage arrangement.
- The outdoor condensing unit sat in the rear garden, accessible via the basement flat, requiring coordinated access across multiple floors.
Our recommendation was to decommission the system, relocate the core hole to achieve the correct fall, and fully recommission — rather than attempt a remedial patch that could compromise the installation in the longer term.
Planning & Preparation
The client had spent a prolonged period trying to get a response from the original installer, which had delayed resolution. Once we were engaged and the survey complete, we issued a detailed written quotation covering the full decommission, rectification and recommissioning. We advised in advance that full access to the lower floors and the rear garden would be needed on the day, and that without it an abortive charge could apply. Access was confirmed ahead of attendance, allowing the works to proceed without delay, and the job was scheduled following sign-off on the quotation.
The Work We Carried Out
- Isolated all electrical and refrigerant supplies before commencing
- Decommissioned the existing installation and safely recovered refrigerant from the full multi-unit system in accordance with F-Gas regulations
- Removed the leaking wall-mounted indoor unit and disconnected the associated condensate pipework
- Drilled a new core hole through the external wall at the correct height and angle to achieve adequate gravity fall
- Reinstalled the existing indoor unit in the correct position and reconnected it with correctly routed condensate pipework
- Carried out a full pressure test of the refrigerant circuit, followed by full evacuation
- Recharged the system with the correct refrigerant specification and quantity
- Recommissioned the full system and confirmed correct operation across all units
A formal written testimonial was not obtained for this project; the client expressed clear satisfaction with the outcome, particularly in contrast to their experience with the original installer. The system was left fully operational, and the works were completed within the agreed timescale and budget.
Timeline & Completion
The works were planned and resourced for a single-day attendance, with two of our engineers — Andrew and Nikola — deployed to move efficiently through the decommission, rectification and recommissioning phases. All works were completed on schedule, within the agreed single-day programme.
Challenges & How We Solved Them
Pinpointing the root cause. A leak from an indoor unit could indicate several faults — a refrigerant issue, a blocked drain, or an installation defect — and an accurate diagnosis was essential to avoid unnecessary work. A thorough inspection confirmed the unit was sound and the fault lay in the condensate pipe routing, specifically a core hole positioned too high. That let us scope the works precisely and avoid dismantling an otherwise correctly functioning system.
Multi-unit refrigerant recovery. Because the affected unit formed part of a multi-split system, refrigerant had to be recovered across the entire system before any mechanical work could begin. Andrew and Nikola worked in tandem through recovery, pressure testing, evacuation and recharge in an organised sequence, confirming the full system was back to correct refrigerant levels and operational before leaving.
Access across multiple levels. The outdoor condensing unit sat in the rear garden, reached via the basement flat, so works required coordinated access across several floors. We set out the access requirements clearly in writing beforehand and the client confirmed arrangements in advance, so our engineers could move freely on the day without delay.
The Finished Result
On completion, the system was fully operational and confirmed leak-free. The new core hole was correctly positioned to give the condensate pipe adequate fall, permanently resolving a drainage fault that had been present since the original installation. The client was left with a Toshiba multi-split system performing exactly as it should — quietly, efficiently and without any water ingress — and a clean finish both inside and out, with no unnecessary damage to the building fabric beyond the single new core hole. After months of inconvenience and an unresponsive original installer, they were able to use their system with confidence for the first time since it was fitted.
Project Investment
The rectification was delivered for a fixed price of £1,854 including VAT. This was a proportionate, targeted investment to permanently resolve a fault that, left unchecked, would have continued to cause water damage, potential mould growth and progressive deterioration of an otherwise sound system. The cost covered full F-Gas-compliant decommissioning and recommissioning, specialist refrigerant handling, and a lasting structural remedy rather than a temporary fix — invariably more cost-effective than repeated call-outs, ongoing water damage or premature replacement.
Why Choose Plumb London
- Honest diagnosis. We fix what needs fixing, not what is easiest to charge for — a proper diagnosis comes before any works.
- Specialist air-conditioning and refrigeration expertise. Fully qualified engineers handling refrigerant in line with F-Gas regulations.
- Transparent, detailed quotations. A clear scope of works with no hidden costs.
- Clear communication at every stage, from survey through to sign-off.
- Lasting quality over quick fixes. We resolve the root cause so the fault does not return.
- A family-run business, trusted by London homeowners and landlords across plumbing, heating and air conditioning.
Frequently Asked Questions
Why is my air-conditioning unit leaking water? The most common cause of water leaking from a wall-mounted indoor unit is a blocked or incorrectly routed condensate drain. Air-conditioning units produce condensation in operation, which must drain outside via a pipe with adequate downward fall. If that pipe lacks sufficient gradient — as here — water cannot drain freely and backs up into the unit, eventually leaking into the room.
Can a leaking air-conditioning unit be repaired, or does it need replacing? Often, as in this project, the unit itself is entirely sound and the fault lies with the installation rather than the equipment. A thorough diagnosis is essential before any decision. Where the unit works correctly and the issue is pipework routing or core-hole position, targeted rectification can resolve the fault permanently without the cost of full replacement.
What is involved in decommissioning and recommissioning an air-conditioning system? Decommissioning means isolating the system, safely recovering the refrigerant via a qualified F-Gas engineer, and removing or repositioning the relevant components. Recommissioning means reconnecting the system, pressure-testing for integrity, evacuating moisture and contaminants, and recharging to the manufacturer’s refrigerant specification before confirming full operation.
How long does air-conditioning repair and recommissioning take? For a project of this nature — a single indoor-unit rectification on a multi-split system — a single day with two engineers is typically sufficient. Larger systems or more complex access can require more time, which is confirmed at the survey and quotation stage.
Customer Testimonials
Don’t just take our word for it, here’s a selection of the latest reviews. You can view more here.
Excellent service by Plumb London, fixed two bathroom related issues in a couple of days - clear communication and good management of expectations in terms of works and timeline, which I always apprec..Read More
Sandra Obradovic
Really happy with the service from Plumb London for my toilet repair. We're quick to attend and Charlie was very knowledgeable, getting the specific part needed and even providing advice on some other..Read More
Darren Phillips
Plumb London were brilliant from quote to completion. Firstly, they are very competitively priced and I had very little hesitation going with their quote for a new boiler. I was also really impressed ..Read More
Ashley Watkinson
Our boiler was leaking and Nicola fixed it the day it happened. Highly recommended!
Kathy Weston
Brilliant service, friendly engineer and a job completed quickly and tidily. I would use the company again if I ever need to. Swanscombe, Kent
Collin Best
Plumb London were able to come quickly and fix my problem without fuss, quoting a sensible price.
Robert Slater
My toilet seat was broken and previous plumbers I contacted told me it was a non-standard toilet and I had to get a new toilet. I invited over Plumb London and they told me that the toilet seat can be..Read More
Geoffrey Payne
Plumb London provided excellent service from start to finish! The boiler installation was quick, tidy, and professionally done. A year later, the same engineer carried out an efficient and thorough ma..Read More
George Ezeanaka
Fantastic experience all around. The customer service team at PlumbLondon is not only responsive and super-friendly, but actually take initiative - we had our job done a day early because a team membe..Read More
Eleanor Franzén
Plumb London carried out a boiler and gas safety check for me. They were quick to get booked in, the team were polite and professional, and their pricing was more competitive than others I contacted. ..Read More
Louise Kaufhold
A Five Star service. The range of skills and craftsmanship displayed by Mounir were incredible. Would recommend to anyone with dreams of creating a Dream Kitchen. With this Team, it’s not just possi..Read More
Trevor Beattie
Easy to communicate with and quick work to solve the problem we had
Josh Evans
Excellent service from start to finish, everything was handled professionally and efficiently. Communication was clear throughout, and Louise did a great job coordinating everything and keeping me in..Read More
Claire Willis
Plumb London were brilliant. Stephan turned up on time, was very personable and was very efficient. Would definitely recommend and will be using again in future.
Eleanor Rider
For the second year in a row, the lovely Mo serviced our boiler. He was on time and provided a super thorough service. I would really recommend Plumb London as your plumbing company. 5 stars all round..Read More
Dianah Jane Coleman
Very fast service. We got our boiler changed as an emergency a year ago, and got service this year. Both times Plumb London were booked within 24h of being called, with the team taking good care of en..Read More
Alexandra Fleming
Great professional service from start to finish. The team did an excellent job installing a Powertank and paid close attention to detail throughout. I’ve used them a couple of times now and have alw..Read More
Kevin Senior
Absolutely exceptional service. Cannot recommend enough. Polite, attentive and understanding of the situation. Par and Stephan who attended my property were courteous and professional, making the horr..Read More
Max Hurd
I can’t fault the service I received. Prompt, courteous and so accommodating. It’s so easy to be ripped off, PlumbLondon are overwhelmingly decent, thorough and reliable. A million percent recomme..Read More
Kate Comer
Amazing job the works is done very professionally I will not hesitate to use your company again and recommend to friends.
Renato Balane
Fantastic service, efficient and easy to organise. Reliable and fair pricing
Jane Renton-Rose
Very professional and comprehensive service.
Stuart Highley
Fast service (next day) for the initial assessment of the issue. Then, even though it was not an emergency per se (needed broken shower pump replaced and associated inter-connecting pipe work), the te..Read More
Jeff Smith
a five-star service
David Akers
I had a great experience with Plumb London. They came out quickly to inspect an issue with my water tank, identified the problem right away, and got everything sorted efficiently. The engineer was pro..Read More
Patrick Fuller
Delighted with the service from Plumb London on a number of occasions. Very reliable and professional.
Thomas Jacques
good job well done boiler replacement
Deirdre Bell
Excellent service from engineer who attended to change kitchen tap. Punctual, courteous and knowledgeable. Got the job done despite an unexpected issue with some complex piping (resolved on the spot)...Read More
Constantia Smith
Contacted Plumb London hi Charlie, come round and give me a quote within days. Carried out. I ordered all the parts and even matched The new tiles with the existing. Hardly recommend them very profess..Read More
Vimal Sharma
Very professional. The work was carried out efficiently and quickly.
matt o'neill
Amazing job the works is done very professionally I will not hesitate to use your company again and recommend to friends.
Renato Balane
Fantastic service, efficient and easy to organise. Reliable and fair pricing
Jane Renton-Rose
We recently worked with Plumb London at AKA Marylebone and were extremely impressed with their professionalism and technical expertise. The project involved complex plantroom systems and ongoing comm..Read More
shellie-ann delaney
Excellent service. I've used Plumb London multiple times and they're always professional (they pick up the phone and arrive when they say they will). For example, my boiler had been leaking but only o..Read More
Sebastian Robinson
The initial consultation from Plumb London was excellent, and then a call received quickly do explain a detailed quote. The appointment for the work was quick and the work to the bathroom carried out ..Read More
Nick M
Had a new boiler installed 4 years ago, best decision. They have looked after it well and every service is efficient, quick and easy. They are fantastic to book with, always answer the phone and any i..Read More
Milly Smith
Big thumbs up for Plumb London, in particular the engineer (Andrew) who visited the property where my elderly mother lives. A gentle manner and patient approach was exactly the level of kindness that ..Read More
Patrick Totty
Prompt and efficient service from Plumb London. A clear and comprehensive quote was provided and the job was completed well. Our ancient boiler completely stopped working and they were able to visit t..Read More
Simone Thomas
Plumb London were absolutely incredible. We were in an emergency situation, and Jack did everything he possibly could to get a new boiler out to us as quickly as possible. He also liaised directly wit..Read More
Lily Macpherson
Fabulous and prompt service. Kept up to date; great communication.
Paula Kennedy
Great job, quick efficient and fair price
Daniel Dean
Delighted with the service from Plumb London on a number of occasions. Very reliable and professional.
Thomas Jacques
The service from Plumb London was prompt and they have solved the problem as I have still not had a complaint from my tenants It was very easy to deal.with the staff at Plumb London.
Shubha Kasbekar
Excellent service from engineer who attended to change kitchen tap. Punctual, courteous and knowledgeable. Got the job done despite an unexpected issue with some complex piping (resolved on the spot)...Read More
Constantia Smith
Excellent service by Plumb London, fixed two bathroom related issues in a couple of days - clear communication and good management of expectations in terms of works and timeline, which I always apprec..Read More
Sandra Obradovic
Really happy with the service from Plumb London for my toilet repair. We're quick to attend and Charlie was very knowledgeable, getting the specific part needed and even providing advice on some other..Read More
Darren Phillips
Contact Plumb London
If you are facing a plumbing, heating, boiler or drainage issue in London, do not hesitate to get in touch with Plumb London. Our friendly and knowledgeable team is ready to assist you with all your plumbing needs. Reach out to us today to schedule a consultation and experience the difference with Plumb London.
