GasFixPRO
GasFixPRO
7 days free. No card needed.

The toolkit every gas engineer needs.

From fault code to certificate in one app.

Unlock Pro and run your whole business from one app.

  • Business Tools: customer database, quotes that become invoices, diary and email service reminders
  • Learning Center: live boiler simulator, how every component works, worked fault finds, flowcharts, regulations and quizzes
  • Everything in Basic: fault codes, manuals, wiring guides, calculators, domestic and LPG certificates with print preview
Basic £3.99 a month, Pro £5.99 a month. 7 days free with full access, no card needed. Cancel anytime. Prices are reviewed every year.
Subscribe NowSee what is included

Your hub

Tap a category to open it. Pro categories unlock with a subscription.

Business Tools PRO

Customers, quotes, invoices, diary and service reminders

Boilers & Diagnostics

Fault codes, manufacturer data and wiring guides

Fault codes

Fault codes and fault finding for each appliance, organised by make and model and copied from the manuals as printed.

Loading...

Manufacturer data

Technical data for each appliance, organised by make and model and copied from the manuals as printed.

Loading...

Wiring guides

Wiring diagrams for each appliance, organised by make and model, taken from the manuals.

Central heating wiring diagramsLoading...

System types and smart controls. Wire colours and terminals differ by manufacturer and model, so always follow the instructions supplied with the product.

Boiler Wiring Diagrams

Loading...

Service mode procedures

How to put each appliance into service mode, organised by make and model and copied from the manuals as printed.

Loading...

Flue gas readings

CO, CO2, O2 and gas rate readings, plus the O2 procedure, for each appliance, organised by make and model and copied from the manuals as printed.

Loading...

Calculators

Gas rate, heat loss, expansion vessel and more

Gas rate

Test a meter over a set time. Enter your initial reading, start the timer, and when it ends enter your final reading. The timer is only a countdown for the test. The result is worked out from your two readings and the test duration you choose.

Time remaining
1:00
More options

The calorific values are typical defaults. Use your supplier's declared value if you have it. Net input is gross divided by 1.11 for natural gas and 1.09 for LPG.

Heat loss

Room by room estimate from the room size, construction and temperatures. It is a steady state estimate using typical U-values and air change rates, not a full BS EN 12831 calculation, so adjust the figures to suit your survey.

Expansion vessel

Minimum expansion vessel size for a sealed heating system, from the water volume, the temperatures and the pressures. It uses the standard gas law method and the expansion of water from 10 °C. Always check it against the vessel maker's data and the boiler's own vessel.

Cylinder reheat

The energy needed to heat a cylinder, and how long that takes or how much power you need. It ignores heat losses and coil efficiency, so treat the time as the quickest it could be.

CO/CO₂ ratio and excess air

Enter the flue gas analyser readings. The ratio is CO in ppm divided by CO₂ as a percentage and then by 10,000. Boilers are commonly checked against a ratio of 0.004, but the maker's own limits come first. Excess air is worked out from the O₂ reading.

Radiator output

Radiators are rated at a mean water temperature 50 K above the room. Enter that rating and your own temperatures to see the real output, which matters for low temperature systems and heat pumps. The exponent is 1.3 for most panel radiators.

Unit converter

Power, energy, pressure, gas flow, volume, length and temperature.

Domestic Certificates

Domestic gas certificates, plus unvented, TMV and legionella

Gas safety record

Fill in the record on screen. Save it to your records, or download a copy to print or send. It is laid out from the checks listed in the Gas Safety (Installation and Use) Regulations, and is your own form, not an official pad.

Saved records

LPG Certificates

LPG safety, service, commissioning and test records

Manuals library

Download the PDF manual for the make and model in front of you.

Looking for a make or model that is not here? Browse all 3,466 models and request one.

Loading the library...

    Service Procedures

    Servicing procedures for each appliance, organised by make and model. Each one shows which manual and page it came from.

    Loading...

    Plans

    Try everything free for 7 days. No card needed. Cancel anytime. Prices are reviewed every year, so they may increase.

    Free trial

    £0 for 7 days
    • Full access to everything in Pro
    • No card needed
    • Pick a plan when it ends
    Start free trial

    Basic

    £3.99 a month
    • Boilers and Diagnostics: fault codes, manuals, wiring, service mode, flue gas readings
    • 9 calculators
    • Domestic certificates
    • LPG certificates
    Choose Basic

    Pro

    £5.99 a month
    • Everything in Basic
    • Business Tools: customers, quotes, invoices, diary and service reminders
    • Learning Center: simulator, component guides, worked faults, flowcharts, regulations and quizzes
    Choose Pro

    Included in Basic

    Home screen with search box and categories
    Search everything from the home screenType a fault code, make, model or GC number and jump straight to the right page. Every category sits underneath.
    A wiring guide diagram
    Wiring guidesS-plan, S-plan Plus, Y-plan, W-plan and smart thermostat diagrams, plus wiring taken from the manufacturer manuals, with how it works and how to check it.
    Gas rate calculator with results
    CalculatorsGas rate, heat loss, expansion vessel, cylinder reheat, combustion ratio, radiator output, units and pipe sizing. The working is shown.
    Gas safety record with print preview
    Domestic certificatesGas Safety Record, service record, commissioning, unvented, TMV and legionella. A print preview shows the A4 landscape page before you print.
    LPG appliance service record with print preview
    LPG certificatesSafety record, appliance service, commissioning, tightness and pressure test, and storage and supply checks, in the same layout.

    Added with Pro

    Customer database
    Customer databaseCustomers, their appliances, GC numbers and next service dates in one place.
    Quotes screen
    QuotesBuild a quote with a live preview, send it, track whether it was accepted, then turn it into an invoice in one tap.
    Invoices screen
    InvoicesSee what is waiting to be paid, overdue or paid, and download a clean invoice for the customer.
    Diary and scheduling
    Diary and schedulingBook jobs against your customers and add them to your phone or Google calendar.
    Service reminders
    Service remindersColour coded list of who is overdue or due soon, with an email reminder that goes out ahead of the date.
    Boiler operation simulator
    Live boiler operation simulatorStep through a combi or system boiler from heat demand to shutdown and watch water, gas, air and flue gas move.
    Components overview diagram
    How components workA professional overview diagram, then every component explained: what it does, how it fails and how to test it.
    Worked fault example with flowchart
    Fault find and repair examplesWorked examples from symptom to checks, cause and repair, each with a flowchart.

    Everything available

    Tap a section to see every tool in it. Screenshots are examples; your own data fills in once you sign in.

    Questions

    Where does the information come from?

    From manufacturer manuals added to the library. Procedures link back to the page they came from.

    Can I download the manuals?

    Yes. Every manual has a PDF download.

    Can it remind my customers about services?

    Yes. Save the service due date against a customer and an email reminder goes out ahead of it.

    Can I cancel whenever I want?

    Yes. There is no contract, and you can cancel from your account at any time.

    Will the price change?

    Prices are reviewed every year, so they may increase. The current prices are shown on the Plans page.

    Is it safe to rely on?

    It is a reference aid. Always follow the manufacturer's instructions and current regulations for the appliance in front of you.