How to Grow a Plumbing Business in the UK
The short answer
Price every job for a team, not for your own day. Then build a servicing book that repeats, hire a second Gas Safe engineer so boilers don't wait for you, and run sales and job costing as systems.
- Price for a team first. An employee on £18 an hour costs about £27.40 per chargeable hour before overheads and profit.
- Build a servicing book. Landlords must have gas appliances checked every 12 months, so that work comes back on its own.
- Stop being the only Gas Safe engineer. If only you can do gas work, every boiler waits for you.
- Grow the work that makes money. Job-cost installs and servicing separately, then grow the one that holds its margin.
Most plumbers hit the same wall. The phone rings all day and the diary is full for weeks. But the business is still you, a van and a set of grips. You can't take more work because there is no more of you.
This guide shows how to grow a plumbing business in the UK past that wall. It covers team pricing, a servicing book, your first hires, the Gas Safe bottleneck and simple systems.
It is written by the owner of a working London construction company who mentors trade business owners one to one. If you want to talk through your own numbers, book a free strategy call.
The four stages of a plumbing business
Every plumbing and heating business we see sits at one of four stages. Each one needs something different from the owner.
- One-man band You quote, fit, commission, invoice and chase. Growth stops at your hours.
- Two or three people You are still on the tools most days, but someone else can do a simple job.
- A team of five to ten You run the prices, the sales and the diary. You pick up tools only when you choose to.
- A company A lead engineer runs the site work and someone runs the office. You run the business.
The five steps below move you from one stage to the next. Skip one and the business usually slides back.
Step 1: price every job for a team
Most one-man bands price for their own day. That price falls apart the moment you pay someone else to do the work.
Our plumbing playbook works it out like this. An employee on £18 an hour costs about £27.40 per chargeable hour once you add National Insurance, pension, holiday and the hours you can't bill. Then add a margin floor: 20% for overheads and 10% for profit makes 30%.
So the lowest price for that hour is £27.40 ÷ 0.70 = £39.14. Below that, every hour your engineer works makes the business poorer. For a worked job from survey to quote, see how to price plumbing jobs.
Kit is where plumbers lose the most. A 30% markup on a boiler only gives a 23% margin. See plumbing business profit margins for the full worked boiler quote.
Not sure where your business is weakest? Take the free 4-minute Construction Business Scorecard. It scores your pipeline, pricing, cash flow and systems, and shows the weakest area first.
Step 2: build work that keeps a team busy
A team needs a steady week, not a full one followed by an empty one. One-off jobs from lead sites rarely give you that. Build work that comes back on its own:
- Landlord gas safety checks: the law says every gas appliance in a let home is checked at least every 12 months. One letting agent can send you a book of renewals.
- Annual boiler servicing: service every boiler you fit and book next year's visit before you leave.
- Heat pumps: installs are zero-rated for VAT until 31 March 2027. But the £7,500 grant is paid to you as the MCS installer, so you carry that cash until it lands.
- Commercial maintenance: schools, offices and landlords need planned servicing and repairs on a contract.
Servicing work pays less per visit but pays fast and fills gaps. Commercial work pays bigger but later. Read how to get commercial plumbing and heating contracts before you price your first package.
Step 3: hire in the right order
Your first hire is someone who can run a simple job without you. That is usually a qualified plumber or heating engineer, not an office manager.
A sensible order for most plumbing businesses:
- An engineer who can run a job. This frees you to quote, sell and check work.
- An apprentice or improver. They make the engineer faster and cost less per hour.
- Part-time admin. Certificates, service reminders, invoices and chasing, so they stop eating your evenings.
- A lead engineer. When two or three jobs run at once and someone has to check the work.
Before each hire, check your prices carry the new wage at your true hourly cost. Can't find anyone? Our guide on what to do when you can't find workers covers adverts, apprentices and keeping staff. For the legal steps, see hiring your first employee.
Ready to hire but not sure your prices can carry a wage?
Book a free strategy call and we'll check the numbers with you.
Step 4: stop being the only Gas Safe engineer
Here is the bottleneck most growth advice misses. By law, only people on the Gas Safe Register may do gas work. If the only registered engineer is you, every boiler swap, service and safety check waits for you.
Your team can strip out, run pipework and fit bathrooms all week. But the gas side stops until you turn up.
The fix is to make your first or second hire a Gas Safe registered engineer. Or train a strong plumber towards it. If you want heat pump work, the same goes for MCS: the grant only works through a certified installer.
UK Plumbing & Heating Profitability Playbook
True hourly cost, margin on kit, call-out minimums and job costing for plumbing and heating, with worked examples.
Get the free guideStep 5: build systems so jobs run without you
A team copies what you do. If nothing is written down, every job runs a different way and you end up checking all of them.
Start with four simple systems:
- A job pack: survey notes, kit list, photos and the client's contact details, ready before day one.
- Commissioning and paperwork: who commissions, who fills in the benchmark and notifications, and when the certificate goes out.
- Service reminders: every boiler you fit or service gets a date for next year in the diary.
- Job costing: hours and kit against the quote on every job.
Job costing is how you know what to grow. In the example in our playbook, a boiler install priced at 30% finished at 19%. Servicing priced at 35% finished at 38%. Without the numbers, that owner would have pushed the wrong work.
Our construction business systems guide shows how to set these up without a big software bill.
What growth looks like: Dmitriy's result
Dmitriy is a plumber with more than 20 years in construction. He had strong skills but no system for winning bigger work.
He changed how he sells. He now presents quotes live, in person or on a call, never just by email. He follows up every open quote every week. He also hands the work to a team and runs projects like an owner. The result: his first £50K commercial project. Individual results, not typical or guaranteed. Read Dmitriy's full story.
That is how Sviat Jay works with owners. He runs Craftex, a London construction company, and mentors owners one to one himself. Every business has different strengths: one owner sells well, another runs jobs well. He finds yours and builds on them. He aims for results in about 4 months, not the 1–3 years many coaching programs take.
Small groups are there for owners who want to start with a lower commitment. If you want to stop being the business and start running it, book a free strategy call, or see how our mentoring programs work.
Mistakes that keep plumbers small
- Hiring before pricing: a new wage on old prices makes you busier and poorer.
- Markup on kit: 30% on cost is only 23% of the price.
- No servicing book: every boiler you fit is a service visit you never booked.
- One Gas Safe engineer: your registration becomes the limit of the business.
- No job costing: without it you can't tell which work to grow and which to drop.
Before your next hire
- Your prices cover about £27.40 per employed hour plus a 30% floor
- Kit is priced on margin, not markup
- Every boiler you fit has next year's service booked
- A second Gas Safe engineer is in your 12-month plan
- Every job is costed against its quote
