Combi swaps, system upgrades, radiator changes, annual services — describe the job and get the kit list, the sizing and the paperwork before you load the van. Radiators and pipe runs worked out, flue kit and inhibitor on the shopping list.
Free plan, no card needed. Pro is £24/month, with 5 days to try it.
Ask, work it out, buy it, tick it off — each step hands to the next. No app hopping.
"Combi swap Thursday, what do I need?" The Gaffer lists the kit and the bits to check before you leave — gas supply pipe size on the run, flue route and clearances, condensate route, system cleanliness.
Radiator output for the room, pipe size for the flow, and the numbers drop into the calculator.
Flue kit, filter, inhibitor, cleaner, TRVs and condensate pipe land on a shopping list with a merchant link on every line.
The install sits on the job's checklist alongside the Benchmark and notification. Tick it as you commission, invoice from the van.
Free, no account needed. Quantities go straight onto a shopping list.
Radiator Sizing
Watts/BTU heat output for a room
Heat output in watts and BTU for a room from size, room type, insulation and external walls — a first pass before the heat loss calc.
Pipe Size & Flow
Velocity check (≤1.5 m/s domestic)
Velocity check for a pipe size and flow, so the run is not undersized and noisy.
AI-generated in under 60 seconds from your job description. Every section editable, shareable, downloadable.
30 years of trade know-how in your pocket. Straight answers to on-site problems, specific to the job you describe — and it reminds you of the bits you'd only remember halfway there.
The Gaffer
Your AI site mate
"Living room 5 by 4 by 2.4 metres, one external wall, double glazed — what radiator output?"
48 cubic metres at a typical 50 watts a cube for a moderately insulated room is around 2.4 kilowatts at a 50 degree delta T. If you are running the boiler to condense with a 55 flow, the same rad gives roughly a third less, so size for that: a 1800 by 600 double panel double convector at around 3 kilowatts at delta T 50 will carry it. Do a proper heat loss calc for the certificate — the rule of thumb is for your first pass, not the paperwork.
Always verify to current regs. On-site conditions may vary.
It gives output in watts and BTU for a room from size, room type, insulation and external walls. Ask the Gaffer to adjust for a lower flow temperature and it will tell you how much to oversize. It is a first pass; do a full heat loss calculation for the certificate.
It reminds you of every stage — notification, Benchmark, commissioning readings, handover — and keeps it on the checklist. It does not submit anything on your behalf. You remain responsible for compliance.
Yes. The same account covers bathrooms, unvented cylinders and pipework. The plumber persona is Gas Safe aware and references Part G, the Water Regulations and unvented rules.