Cylinder sizing
Size a hot water cylinder from real peak demand rather than occupancy - including why coil surface area matters as much as volume.
Read more →Short answer
Free calculators and checkers built from published standards and regulation. No email address required, nothing stored, nothing sold on. Where a tool is not yet built, the page says so.
The principles
- Free, and genuinely free. No email address, no registration, no ‘enter your details to see the result’.
- Nothing stored. Calculations happen in your browser and nothing is retained.
- Nothing sold on. Your figures are yours.
- Built from published sources. Regulation, standards and government statistics, with the source named.
- Honest about what they cannot do. Where a tool cannot produce a number because we have no defensible source, it says so rather than guessing.
- Honest about what is not built yet. Several of these are architecture rather than live pages, and they say so on the page.
Why no email gate
Because a tool behind a form is not a tool, it is a lead magnet. If something we have built is useful to you and you never contact us, that is a perfectly good outcome – and it is why people come back.
What is here
| Tool | What it does | Status |
|---|---|---|
| Water hardness checker | Classification bands, unit conversions, and what your figure means for equipment | Built |
| Heating oil comparison | Compare quotes on a like-for-like basis, rather than headline price per litre | Built |
| Repair or replace? | Structures the decision around the factors that actually matter | In development |
| Running cost comparator | Oil, gas and heat pump compared using your building’s figures | In development |
| Cylinder sizing | Sized from real peak demand, with coil area weighted properly | In development |
| Emergency triage | Whether it needs somebody tonight, tomorrow, or next week | In development |
| D2 discharge pipe sizing | Whether an unvented cylinder’s discharge run is compliant | In development |
| F-Gas calculator | CO2e from refrigerant and charge, and the resulting obligations | In development |
| Oil tank usage estimator | How long what is in the tank will last, and when to reorder | In development |
Each page describes the method whether or not the tool is live, because the method is the useful part and you can work through it with us in the meantime.
Why some of them refuse to give you a number
Three tools deliberately stop short of producing a figure, and it is worth explaining rather than leaving it looking like an omission.
The water hardness checker will not tell you your postcode’s figure
Plenty of sites will. Those numbers are third-party aggregations whose provenance we have not verified against the water company, and we are not prepared to publish a figure we cannot stand behind. Anglian Water publishes the authoritative figure for your supply zone.
The heating oil tool will not tell you the price
We have no licensed source for heating oil price data. Scraping comparison sites breaches their terms and engages database right, and building a page on a foundation that can be withdrawn at any time would be a poor decision. So it helps you compare quotes you have obtained instead.
The running cost comparator will not publish fuel prices
Same reason. You enter the prices you can actually obtain, which is more accurate for your situation anyway.
The general position is set out at what things cost.
What we would build next
Ordered by how useful we think they would be, rather than by how easy:
- A genuine local price index from our own completed jobs. The single most valuable thing we could publish, and the one that takes longest to accumulate.
- The F-Gas calculator, because it is the obligation most operators do not know they have and the arithmetic is genuinely off-putting.
- Emergency triage, because it would resolve calls at the moment people most need an answer.
- Cylinder sizing, because the coil question is so consistently missed.
- A heat loss estimator, which would make the heat pump conversation far more concrete for people.
If one of those would be useful to you, say so – it affects the order.
Working through a calculation and stuck? Call. The methods behind these tools are what we use in practice and you are welcome to use us instead.
Questions we get asked about this
Do I have to give an email address?
No. Nothing here is gated and nothing requires registration. If a tool is useful to you and you never contact us, that is a fine outcome.
Are my figures stored?
No. Calculations happen in your browser and nothing is retained or sold on.
Why are some tools not available?
They are in the architecture and not yet built. Each page describes the method anyway, because that is the useful part and you can work through it with us in the meantime.
Why will the tools not tell me prices?
Because we have no licensed source for the price data in question and we will not publish figures we cannot stand behind. We would rather help you compare quotes you have obtained.
Where do the numbers in the tools come from?
Published regulation, standards and government statistics, with the source named on each page. Where we cannot source something, the tool says so.
Can you build one for my situation?
Tell us what would be useful. The order we build these in is influenced by what people actually ask for.
Regulations and standards referenced on this page
- Regulation (EU) No 517/2014 on fluorinated greenhouse gases, as retained and amended in GB law — UK Statute Law Database
- Fluorinated gases (F gases): guidance for operators and engineers — Environment Agency / Defra
Services
What we cover
D2 discharge pipe sizing
Work out whether an unvented cylinder's D2 discharge pipe is correctly sized, including the equivalent length allowance for bends.
Read more →Emergency triage
Work out whether a plumbing problem needs somebody tonight, tomorrow, or next week - and what to do right now.
Read more →F-Gas compliance calculator
Calculate a system's CO2e from refrigerant type and charge, and find the resulting leak check frequency and obligations.
Read more →Heating oil cost and quote comparison
Compare heating oil quotes properly - order size, delivery terms and the things that make two prices not comparable.
Read more →Oil tank usage estimator
Estimate how long the oil in your tank will last and when to reorder - based on your own consumption rather than a rule of thumb.
Read more →Oil vs gas vs heat pump running costs
Compare heating running costs properly - the method, the variables that dominate, and why published comparisons mislead.
Read more →Repair or replace?
A structured way to decide whether to repair or replace a boiler, cylinder or oil tank - the factors that actually matter.
Read more →Water hardness checker
Understand water hardness classifications, convert between units, and find out what your hardness figure actually means for your plumbing.
Read more →Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.