Written by
Sarah Nguyen
Published on
Jan 25, 2026
Low boiler pressure is one of the most common maintenance calls letting agents receive. It's also one of the most frequently resolved without an engineer visit — if tenants know what to check.
The problem is, most tenants don't. They see the boiler isn't working, they call you, you call a contractor, the contractor shows up and repressurises the system in two minutes. Everyone's time is wasted, and someone's paying for a callout that didn't need to happen.
This guide explains boiler pressure in plain English, walks through what tenants can safely do themselves, and gives you a ready-to-use template to send when these calls come in.
Why Boiler Pressure Calls Are Worth Getting Right
Low boiler pressure isn't usually an emergency. But it does stop the heating and hot water from working — which means tenants report it as urgent, and rightly expect a fast response.
The good news: in many cases, repressurising a boiler takes five minutes and requires no tools or expertise. Tenants can do it themselves if they're given clear instructions.
The catch: if you send generic advice or nothing at all, tenants either can't fix it (and you still need a callout) or they do something wrong (and you've got a bigger problem).
Getting this right means:
Fewer unnecessary callouts — saving money and contractor capacity for genuine emergencies
Faster resolution for tenants — they fix it in minutes rather than waiting days for an engineer
Better tenant relationships — you've empowered them rather than leaving them in the dark
Clear escalation paths — when self-service doesn't work, you know it's a real issue
Boiler Pressure: The 60-Second Explainer
Before you can explain this to tenants, you need to understand it yourself. Here's the short version.
What boiler pressure actually is: A combi boiler heats water and circulates it through your radiators and taps. The "pressure" refers to the pressure of water inside this sealed system. Too little water = too little pressure = boiler cuts out as a safety measure.
What the pressure gauge shows: Every combi boiler has a pressure gauge on the front panel — either a dial with a needle or a digital display. It measures pressure in "bar."
The normal range:
1 to 1.5 bar when the heating is off (cold)
Up to 2 bar when the heating is running (hot water expands)
Below 1 bar = too low, boiler may not fire
Above 2.5 bar = too high, pressure relief valve may release water
Why it drops:
Bleeding radiators (releases air but also loses some water)
Small leaks in the system (pipes, radiators, boiler itself)
Pressure relief valve releasing excess pressure
Natural loss over time (all sealed systems lose a little)
That's it. If a tenant understands this, they can make sense of what's happening and follow instructions to fix it.
What Tenants Can Safely Check and Fix
Step 1: Check the pressure gauge
Ask the tenant to look at the boiler's front panel and find the pressure gauge. On most boilers, it's a small dial with numbers from 0 to 4.
If the needle is in the green zone (1–1.5 bar): Pressure is fine. The problem is something else — move to other diagnostics.
If the needle is below 1 bar (often a red zone): Low pressure. This is likely why the boiler isn't working.
If the needle is above 2.5 bar: High pressure. The tenant should not add more water. This may need professional attention.
Step 2: Repressurise the boiler (if pressure is low)
This is the fix for low pressure. It involves adding water to the system via the "filling loop" — a small valve or flexible hose that connects the boiler to the mains water supply.
Before they start:
Turn the boiler off and let it cool for 10–15 minutes
Have the boiler manual handy if possible (many are available online by searching the model number)
Locate the filling loop — usually underneath the boiler, a silver braided hose with valves at each end
The process:
Check the filling loop is securely connected at both ends
Open the valves slowly — one at a time or both together depending on the model. The tenant should hear water flowing into the system
Watch the pressure gauge — it will rise as water enters
Stop when it reaches 1 to 1.5 bar — don't overfill
Close the valves — make sure they're fully closed to prevent overfilling later
Turn the boiler back on — some models require a reset button to be pressed
Important notes:
Some boilers have a built-in filling key rather than a hose — the manual will explain
If the tenant can't find the filling loop or isn't sure, they shouldn't guess. Better to wait for an engineer than cause damage
A small amount of water dripping when disconnecting the hose is normal
Step 3: Check if it holds
After repressurising, the tenant should monitor the gauge over the next few days.
If pressure stays stable: Problem solved. It was just natural loss or post-radiator-bleeding drop.
If pressure drops again within days: There's likely a leak somewhere. This needs professional investigation.
When to Escalate to an Engineer
Repressurising is a temporary fix if there's an underlying issue. The tenant should report back (and you should send a contractor) if:
Pressure drops repeatedly — needs repressurising more than once a month suggests a leak
They can't find the filling loop — not all boilers have an obvious one, some need a key
The gauge is already in the normal range — pressure isn't the problem
Pressure is too high — don't add water, may need pressure relief valve check
Visible water or damp around the boiler, pipes, or radiators — leak confirmed
Boiler displays an error code after repressurising — separate fault
Unusual noises from the boiler (banging, kettling, gurgling) — may indicate sludge or trapped air
The tenant isn't comfortable doing it — never pressure someone to DIY if they're unsure
If the issue turns out to be a leak, that's a landlord responsibility under Section 11 of the Landlord and Tenant Act 1985. The engineer will need to locate and repair it. Small leaks at radiator valves are common and usually straightforward; leaks inside the boiler are more complex.
Template Message: What to Send Tenants
Here's a ready-to-use message you can send when a tenant reports their boiler isn't working and you suspect low pressure:
Subject: Boiler not working? Here's what to check
Hi [Name],
Thanks for letting us know about the boiler issue. Before we send an engineer, this might be something you can fix yourself in a few minutes.
Step 1: Check the pressure gauge Look at the front of your boiler for a small dial or digital display showing pressure in "bar." It should read between 1 and 1.5. If it's below 1, that's likely why the boiler isn't working.
Step 2: Repressurise the boiler If the pressure is low, you can top it up:
Turn off the boiler and wait 10 minutes for it to cool
Find the filling loop — usually a silver braided hose underneath the boiler
Open the valves slowly and watch the pressure gauge rise
Stop when it reaches 1 to 1.5 bar
Close the valves fully
Turn the boiler back on
If you're not sure where the filling loop is, search your boiler model online — most manufacturers have video guides.
Step 3: Let us know If this fixes it, great — no engineer needed. If the pressure drops again within a few days, or you can't find the filling loop, let us know and we'll send someone out.
Don't attempt this if:
The pressure is already in the normal range (1–1.5 bar)
The pressure is too high (above 2 bar)
You see water leaking anywhere
You're not comfortable doing it
Just reply to this message and we'll arrange an engineer.
Best, [Your name]
Feel free to adapt this for your tone and branding. The key elements are: clear instructions, explicit permission to escalate, and reassurance that it's okay to ask for help.
Preventing Repeat Pressure Issues
If you're seeing frequent low-pressure calls across your portfolio, a few proactive steps can reduce them:
Educate tenants at check-in: A quick walkthrough of the boiler — where the pressure gauge is, what normal looks like, how to repressurise — can prevent dozens of calls over a tenancy. Five minutes at move-in saves hours over the year.
Include guidance in the welcome pack: A one-page boiler guide with photos of the specific model in the property. Many manufacturers provide these, or you can create a simple template.
Schedule annual boiler servicing: Not legally required (the annual gas safety check is a separate requirement), but servicing catches issues before they become breakdowns. Engineers will check and adjust pressure as part of a standard service.
Check pressure during routine inspections: If you or your contractor are in the property for any reason, a quick glance at the boiler gauge takes seconds. Catching low pressure early prevents emergency calls later.
Investigate repeat issues: If the same property keeps losing pressure, there's probably a slow leak. It's worth paying for a proper diagnosis rather than endless repressurising. Small leaks can also cause damp and mould issues if left unchecked.
When Low Pressure Becomes No Hot Water
Low boiler pressure is a nuisance. But if it causes a complete loss of hot water or heating, the urgency escalates.
Under the legal framework — Section 11 of the Landlord and Tenant Act 1985 and the Homes (Fitness for Human Habitation) Act 2018 — landlords must keep heating and hot water systems in repair and proper working order. For social housing, Awaab's Law now mandates specific response times for hazards, and similar requirements are expected to extend to the private rented sector.
If a tenant reports low pressure and can't fix it themselves — or if repressurising doesn't restore hot water — treat it as an urgent repair. For a full triage framework, see our guide on handling no hot water reports.
Documentation Matters
Even for a minor issue like low pressure, keep a record:
Date and time the tenant reported the issue
Guidance sent (save a copy of the message)
Tenant's response — did they fix it themselves or need an engineer?
Outcome — resolved by tenant, engineer attended, or underlying issue found
This might seem like overkill for a five-minute fix. But if the same tenant later claims they were "left without heating for weeks," your documentation tells the real story.
For more on building a robust record-keeping process, see our guide on creating an audit trail for property repairs.
The Bottom Line
Low boiler pressure is common, usually harmless, and often tenant-fixable. The letting agents who handle it well aren't the ones with the fastest contractor response times — they're the ones with clear processes that help tenants help themselves.
Send the right guidance upfront. Make it easy for tenants to report back. Escalate when needed. Document everything.
Do that, and boiler pressure calls become a two-minute email rather than a two-day headache.
Lanten handles tenant repair requests automatically — sending the right guidance, collecting diagnostic information, and escalating to contractors when self-service doesn't work. Every step is documented without you lifting a finger. Book a demo to see how it works.
