“Manometer” is a wider word than it sounds on a survey report. Two quite different site jobs both come down to reading a differential pressure accurately and writing it down: a Gas Safe engineer’s gas tightness test on an installation’s pipework, and a retrofit assessor’s ventilation commissioning check on an extract or MVHR system. Both use an instrument that does the same basic thing — measures the difference between two pressures — over completely different ranges, for completely different reasons.
I’m a building surveyor, not a gas engineer, and the tightness test itself isn’t something I run. What I see on a survey is what sits either side of it — a gas safety certificate with a date that’s quietly slipped past twelve months, or an installation that’s clearly had work done to it since the last inspection. The test that closes that loop, run under IGEM/UP/1, starts with a let-by check at 7–10 mbar and moves to a tightness test proper at 20–21 mbar for natural gas or 37 mbar for LPG, held and timed against a permissible pressure drop. The manometer is the instrument that produces the number a Gas Safe engineer signs against.
The other job is closer to my own work. When I measure ventilation on a retrofit assessment — checking a System 1 to System 4 setup is actually moving the air it’s supposed to — most terminals give a clean reading from a vane anemometer held against the grille. Not every terminal cooperates: an awkward duct run, a terminal too small for the vane, or a system being commissioned against Approved Document F’s flow targets, mandatory since June 2022, calls for a pressure-based method instead — a flow ring or orifice plate matched against a manometer reading, or a proper airflow-and-pressure instrument that does both. That’s the gap this guide covers.
The one I’d buy
Anton APM 135
Anton is a name most Gas Safe engineers already have other test kit from, and the APM 135’s own listing states it’s built for exactly this job: −40 to +130 mbar comfortably spans the 7–10 mbar let-by check and the 20–21 mbar (natural gas) or 37 mbar (LPG) tightness test that follows it, with resolution stepping down to 0.01 mbar below 20 mbar — the precision the test actually needs. Min/Max recording and a push-button zero round it out, without the price jump of a data-logging or airflow-capable instrument most gas work never touches.
Typically £130–£170
Check price on AmazonHow I judge a manometer
Range matched to the job, not a single headline spec. A gas tightness kit needs to comfortably span 7–10 mbar for the let-by check and 20–21 mbar (natural gas) or 37 mbar (LPG) for the tightness test that follows; a ventilation commissioning instrument is better judged on its Pa range and whether it reads airflow or velocity alongside pressure, not on a mbar figure built for gas work.
Resolution at the pressure the test actually runs at. A headline “±1% of full scale” figure is close to meaningless without checking what that works out to at 20 mbar specifically — the units here that step down to 0.01 mbar below 20 mbar are reading to a precision the tightness test needs, not just a precision that looks good on the box.
Min/Max or data hold, to catch a transient drop. A pressure drop during a tightness test can happen between glances at the display. A unit that records the minimum and maximum reading over the test period is doing the watching so the engineer doesn’t have to stare at a needle for the full duration.
Digital convenience against a manual gauge that can’t fail electronically. A U-tube manometer has no battery to go flat and no sensor to drift out of calibration between services. It’s still explicitly permitted under IGEM/UP/1, and worth keeping as a backup even where a digital instrument is the daily tool.
A stored or logged reading, for the paperwork. Since Approved Document F made ventilation commissioning mandatory in June 2022, a commissioning notice has to reach Building Control within five days of the work. A unit that stores or exports readings makes that record easier to produce than a phone photo of a display.
The comparison
| Model | Range | Type | Typical price | Best for | |
|---|---|---|---|---|---|
| Anton APM 135 | −40 to +130 mbar | Digital | ~£130–£170 | Best overall | View |
| Testo 510i | 0–150 hPa (mbar) | Digital (Bluetooth) | ~£120–£155 | Best on a budget | View |
| Testo 510 | 0–100 hPa (mbar) | Digital | ~£130–£205 | Standalone display | View |
| Extech HD755 | ±0.5 psi (~±34 mbar) | Digital (USB log) | ~£190–£230 | USB data logging | View |
| UEi EM201B | ±100 mbar | Digital | ~£185–£220 | Rugged dual-input | View |
| Fluke 922 | ±40 mbar + airflow/cfm | Digital | ~£850–£950 | Premium/professional pick | View |
| Rothenberger 67064 | 0–30 mbar (typical) | Manual U-gauge | ~£30–£40 | Cheapest / manual backup | View |
The picks in detail
Anton APM 135
Best overall — purpose-built for the domestic pressure-test range
This is the top pick above: −40 to +130 mbar covers the let-by check and the tightness test with headroom either side, resolution steps down to 0.01 mbar below 20 mbar, and Min/Max recording plus a push-button zero handle the parts of the test that are easy to miss watching a display in real time. It doesn’t log to an app or a PC, and runs on 3×AA batteries rather than a rechargeable pack — the trade-off for a single, purpose-marketed instrument at a sensible price.
For
- Range covers let-by and tightness tests without switching instruments
- 0.01 mbar resolution below 20 mbar
- Min/Max recording and push-button zero built in
Against
- No data logging or app export
- 3×AA batteries only, no rechargeable option
Typically £130–£170
Check price on AmazonTesto 510i
Best on a budget — the cheapest genuinely digital option, display on your phone
Testo’s name carries the same weight in pressure and flow testing that it does in flue gas analysis, and the 510i is the pared-back way into that ecosystem: a Bluetooth smart probe with no built-in screen, reading differential pressure, static pressure and — with the right accessory — air and volume flow straight to the free Testo Smart App on a phone or tablet already on site. That keeps the unit compact and the price below even the standalone 510, though the reading only exists where the app can see it, which is awkward in a signal-dead loft or basement plant room.
For
- Cheapest genuinely digital option here
- Logs and screenshots straight to a phone via Bluetooth
- Magnetic back for hands-free mounting
Against
- No standalone display — needs a phone or tablet running the app
- Pitot tube for airflow readings sold separately
Typically £120–£155
Check price on AmazonTesto 510
Standalone display — no app or pairing required
Where the 510i hands the display to a phone, the standard 510 keeps its own backlit screen, automatic temperature and air-density compensation, and a straightforward button interface that needs nothing paired or charged to read. Its 0–100 hPa range covers the tightness-test range with headroom to spare, and it accepts a pitot tube for basic airflow readings. Amazon isn’t always the cheapest place to buy one; some trade suppliers undercut it by £20–£40.
For
- Standalone backlit display, no app or pairing needed
- Automatic temperature/air-density compensation
- Pitot-compatible for basic airflow work
Against
- No Bluetooth or logging
- Some trade suppliers price it lower than Amazon
Typically £130–£205
Check price on AmazonExtech HD755
USB data-logging pick — a stored record, not just a display
The HD755’s headline feature is one most of the rest of this list lacks: a built-in USB port that logs readings straight to a PC, alongside on-unit Max/Min/Average capture with a timestamp. That’s worth the premium over the Anton and both Testo picks where the record needs to stand up to Building Control. Its ±0.5 psi range suits ventilation and duct pressure work but is tighter than ideal for the top end of an LPG tightness test.
For
- Built-in USB logging to a PC with timestamped readings
- Max/Min/Average capture
- Backlit display in a hard case
Against
- Narrower range than the gas-trade picks here
- Stock has run low before — worth checking availability
Typically £190–£230
Check price on AmazonUEi EM201B
Rugged dual-input pick — two ports, one reading
UEi is a US brand with a smaller UK footprint than Testo or Anton, but the EM201B’s dual-input design and rugged metal fittings suit a genuinely rough working life — dropped in a toolbox, used outdoors, left in a cold van overnight. Its ±100 mbar range and 40-hour-plus battery life cover the tightness test comfortably, with dynamic resettable Min/Max for one-handed use. Priced close to the Extech without the USB logging, the case for it over the cheaper Anton comes down to the dual ports specifically.
For
- Dual-input ports for differential readings from two points at once
- Rugged metal fittings
- 40+ hour battery life
Against
- No USB or Bluetooth logging
- Smaller UK stockist network than Testo or Anton for warranty support
Typically £185–£220
Check price on AmazonFluke 922
Premium/professional pick — built for MVHR and duct commissioning, not just a tightness test
The 922 is a different order of instrument to everything else on this page: differential and static pressure, air velocity and calculated cfm in one unit, colour-coded hoses to stop a port being read the wrong way round, and 99-reading on-board storage for a commissioning record that goes beyond a single static figure. That combination is built for what Approved Document F commissioning has demanded since it became mandatory in June 2022 — flow at every terminal, balanced within tolerance, recorded. It’s a serious step up in price over everything else here, and most of that capability sits unused on a routine gas tightness test.
For
- Pressure, velocity and cfm airflow all in one instrument
- Colour-coded hoses and duct-shape input for direct flow readings
- 99-reading on-board storage
Against
- The most expensive instrument in this guide by a wide margin
- Most of its capability is wasted on a simple gas tightness test
Typically £850–£950
Check price on AmazonRothenberger 67064
The manual option — no battery, no calibration drift, still permitted
A U-tube water-column gauge is the oldest way to make this measurement, and it’s still a legitimate one: IGEM/UP/1 doesn’t require a digital display, only an accurate reading, and a manometer full of gauge fluid can’t suffer a flat battery or sensor drift between calibrations. What it can’t do is log a reading, hold a Min/Max, or read to the resolution a digital instrument manages below 20 mbar — worth keeping as a backup in the door pocket rather than a primary instrument for anyone testing regularly.
For
- No battery or calibration drift to manage
- Genuinely permitted alongside digital instruments under IGEM/UP/1
- Lowest price here by a wide margin
Against
- No digital display, Min/Max or logging
- Resolution depends on reading a column by eye
Typically £30–£40
Check price on AmazonWhat actually matters — and what doesn’t
Airflow and cfm capability is wasted on a pure gas tightness kit. The Fluke 922’s velocity and calculated-flow readings earn their keep on MVHR and duct commissioning, where the question is how much air is moving, not just what the pressure is — on a routine domestic tightness test, that capability goes entirely unused.
A high pressure ceiling matters for airflow work, not for a domestic gas test. Every gas tightness test on this page runs well under 40 mbar; a unit rated to several hundred mbar or more is answering a question a domestic gas installation never asks.
Bluetooth and app logging is convenience, not compliance. A dated, saved reading from an app is a tidy record, but it isn’t the only acceptable one — a written figure and a photo of the display have done the job for years. It’s worth paying for if the paperwork process genuinely benefits from it, not as a default upgrade.
A U-gauge isn’t obsolete kit. It’s slower to read and can’t log a result, but it remains a legitimate instrument under IGEM/UP/1 and one that never needs a battery changing mid-job — worth keeping in the van even where a digital instrument is the daily tool.
Electrical CAT ratings don’t apply here. That’s the relevant safety marking on a clamp meter or multimeter working near live wiring; a manometer’s relevant reference points are IGEM/UP/1 for gas work and Approved Document F for ventilation commissioning, and neither has anything to do with electrical category ratings.
Questions I get asked
What’s the difference between a manometer and an anemometer?
A manometer measures pressure — the difference between two points, in mbar, Pa or inches of water column. An anemometer measures air velocity directly, usually with a spinning vane held in the airstream, and converts that to a flow rate. Both get used on a ventilation commissioning visit; a vane anemometer reads most terminals directly, while a manometer earns its place where the terminal geometry makes a direct vane reading unreliable, paired with a flow ring or orifice plate.
Does a Gas Safe engineer have to use a specific type of manometer for a tightness test?
IGEM/UP/1 doesn’t mandate a digital instrument — a calibrated U-gauge is still permitted alongside an electronic one, provided it reads accurately enough for the pressures involved and is checked or calibrated regularly. What matters is the reading’s accuracy and the engineer’s competence in running the test, not the specific model of gauge used.
Can the same manometer be used for both gas tightness testing and ventilation commissioning?
For the pressure reading itself, yes — the physics is identical, just at different scales. Where it gets awkward is range and resolution: an instrument set up for 0–40 mbar gas work reads a domestic ventilation pressure of a few hundred Pa (roughly 0–4 mbar) at the coarse end of its scale, which is why a dedicated commissioning instrument like the Fluke 922 pairs pressure with a direct velocity and flow reading instead of relying on pressure alone.
How often does a digital manometer need calibrating?
Commonly annually against a traceable reference, in line with how most gas test instruments are serviced — check the specific manufacturer’s guidance for the unit bought, since intervals vary. A manometer that’s been dropped, stored somewhere damp, or is giving a reading that looks obviously wrong is worth checking before it’s trusted again, regardless of when the last calibration fell due.
A manometer is the instrument behind two very different sign-offs: a Gas Safe engineer’s tightness test on the pipework, and a retrofit assessor’s commissioning check that a ventilation system is moving the air it’s designed to once a home’s been tightened up. If you’re a homeowner or landlord chasing a gas safety certificate, or want a retrofit assessment that checks ventilation is keeping pace with the rest of the work, get in touch — or browse the rest of the field-kit guides, including the anemometer guide this one sits alongside.
Disclaimer. This guide is general information, not a substitute for a gas tightness test by a registered Gas Safe engineer or a ventilation commissioning check by a qualified assessor. Prices are indicative, move constantly and were checked at the time of writing; the linked page always shows the current price. As an Amazon Associate I earn from qualifying purchases.