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The correct pressure on a combi boiler

On an Ideal Logic combi, the user guide says to check the gauge is between 1 and 1.5 bar, and it calls 1 to 2 bar the original installation pressure [S5]. If you suspect the appliance is unsafe, turn it off and get a Gas Safe registered engineer to check it [S2].

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By the QuoteZila editorial team. Editorial policy.

What the Logic combi guide says about pressure

Ideal's Logic Combi user's guide, for the 24, 30 and 35, says that if the display shows low water pressure you should check the system pressure is between 1 and 1.5 bar on the gauge [S5]. The same guide calls 1 to 2 bar the original installation pressure, and says a fall below that over time may indicate a water leak [S5]. It says the boiler will not operate if the pressure has reduced to less than 0.3 bar [S5]. If the pressure keeps dropping, the guide says to consult a Gas Safe registered engineer [S5].

That band is for those Logic models. Another combi can name a different one. Gas Safe Register's consumer inspection factsheet (February 2026, version 6) asks you to have the manufacturer's instructions available for a visit [S1]. If they are missing, the inspector may be limited to a visual look and may not run operational checks [S1]. Put the booklet where the engineer can read it. If you have lost it, say so.

If you suspect the appliance is unsafe

The HSE domestic gas FAQ says it is illegal to use a gas appliance you suspect is unsafe [S2]. Turn it off and do not touch it until a Gas Safe registered engineer has checked it [S2]. That is the whole instruction for an unsafe appliance. It is not a repair method.

HSE strongly advises an annual service of appliances, flues and pipework by a Gas Safe registered engineer [S2]. "Annual" here is HSE's word, not a QuoteZila interval.

Gas Safe Register. QuoteZila is not affiliated with this organisation.

What an inspection may include

The factsheet's list for gas-fed appliances, subject to access, includes ventilation, the chimney or flue, and pressure-relief termination [S1]. It also includes the condensate discharge pipe, its size, support and termination [S1]. Those are checks an inspector may make. They are not a home workbook. The inspector will not go into spaces that are inaccessible, that would mean damaging the house, or that pose an unacceptable risk. The examples given include a roof, a loft without suitable access, and pipework concealed in walls or under floors [S1].

Cheshire, and the appliance in front of you

Crewe, Nantwich and Sandbach are where QuoteZila is starting. Anyone in the UK can still post a job or register a business [QZ5]. When you post, name the make and model if you know them, say whether you have the instructions, and say whether you have already switched the appliance off because you suspect it is unsafe.

Citizens Advice says to get written quotes from at least three traders for home work, and to ask to see insurance [S3]. For gas work, the registration check comes first [S2]. A business registers for VAT when taxable turnover for the last 12 months goes over £90,000 [S4]. Ask whether the service price includes VAT [S3].

Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.

Up to five matched local businesses can send quotes [QZ2]. QuoteZila is free for customers and local businesses [QZ1].

Posting a job is not open yet

Read heating engineers and plumbers. Plumber cost is about reading a written price. Electrician cost in Cheshire is a different trade, linked because a heating job sometimes sits next to wiring. Leave that wiring to an electrician.

This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.

Jobs you might post

These are examples, not taken from real job posts.

  • "Combi boiler in Crewe. Gauge reading I do not understand. Instructions are in the kitchen drawer. Please do not ask me to adjust anything before you arrive."
  • "Boiler in Nantwich switched off because it smelt wrong. Gas Safe visit. I will not turn it back on."
  • "Annual service in Sandbach. Model on a photo. I want the engineer to say what the instructions require, in writing, after the visit."

Questions about boiler pressure

What pressure should the gauge on a combi show?

Ideal's Logic Combi user guide, for the 24, 30 and 35, says to check that system pressure is between 1 and 1.5 bar when the display shows low water pressure. The same guide calls 1 to 2 bar the original installation pressure, and says the boiler will not operate if the pressure has reduced to less than 0.3 bar. Another model can name a different band. Gas Safe Register's inspection factsheet says you should have the manufacturer's instructions ready for a visit. Ask the engineer to read the booklet for the appliance in front of you.

What if I think the boiler is unsafe?

HSE says it is illegal for anyone to use a gas appliance they suspect is unsafe. Turn the appliance off and do not touch it until a Gas Safe registered engineer has checked it. HSE also strongly advises that gas appliances, flues and pipework are installed and serviced at least annually by a Gas Safe registered engineer. Leave the filling loop and the case to a Gas Safe registered engineer.

Does the inspection sheet mention pressure?

It lists pressure-relief termination among checks on a gas-fed boiler, where access allows, along with ventilation and the flue. That is the relief route, not the 1 to 1.5 bar gauge check in the Logic combi guide. The sheet also says an inspector will not inspect parts that are not accessible, that would damage the property if accessed, or that pose an unacceptable risk. A cupboard built tight around the boiler can be one of those limits. Say so when you book the visit.

Who is allowed to work on the boiler?

HSE says anyone employed to work on gas appliances in a home must be a Gas Safe registered engineer, competent for that work. Competencies are marked on the back of the engineer's ID card. You can check the engineer on the Gas Safe Register or by calling 0800 408 5500. QuoteZila does not do that check for you.

Does QuoteZila check the businesses?

No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.

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Sources

  1. QZ1: QuoteZila product fact. QuoteZila public pricing line.
  2. QZ2: QuoteZila product fact. QuoteZila terms, customers.
  3. QZ5: QuoteZila product fact. QuoteZila coverage wording.
  4. S1: Gas Safe Register visit information for consumers, factsheet v6, Gas Safe Register. Accessed 2026-10-25. https://www.gassaferegister.co.uk/media/ykxo3tst/gas-safety-consumer-inspection-guide-factsheet-v6-final.pdf
  5. S2: Domestic gas: frequently asked questions, HSE. Accessed 2026-10-25. https://www.hse.gov.uk/gas/domestic/faqs.htm
  6. S3: Before you get work done on your home, Citizens Advice. Accessed 2026-10-25. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
  7. S4: Register for VAT, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/register-for-vat
  8. S5: Logic Combi 24, 30, 35 user's guide, Ideal, copy hosted by Bristol City Council. Accessed 2026-10-27. https://www.bristol.gov.uk/files/documents/2222-ideal-logic-combi-boiler/file