A manometer is the one gas tool you can't fake a job without. Every regulator set-up, appliance commission and pressure check ends with a reading, and that reading is only as good as the instrument and how it's connected. The HT-1891 digital manometer (Bromic 8688951, $218.94) is one of the most-ordered tools on our site. This guide covers what its specification actually means on the job, so you know when to trust the number and when to reach for something else.
The specification, in plain terms
| Spec | Listed value | What it means on site |
|---|---|---|
| Measuring range | ±34.47 kPa | Covers appliance and low-pressure consumer piping comfortably. 34.47 kPa is 5 psi. |
| Accuracy | ±0.3% FSO at 25°C | ±0.3% of full scale, so about ±0.10 kPa anywhere in the range (see below). |
| Repeatability | ±0.2% | Readings taken the same way should agree closely, which is what matters for a pressure drop test. |
| Max pressure before failure | 137 kPa (20 psi) | Never connect it upstream of a regulator on an elevated or high-pressure supply. |
| Units | 11 | Switch to kPa to match Australian appliance data plates. |
| Operating temperature | 0–50°C | Fine for most sites; let it settle if it's come out of a hot ute. |
| Power | 1 x 9V battery | Carry a spare; low battery is indicated on screen. |
Functions listed are a backlit dual LCD, data hold, a record function showing maximum, minimum and average, low battery and over/under range indication, and auto power off.
What “±0.3% FSO” means at appliance pressures
FSO is full scale output. The error band is a percentage of the whole range, not of the reading. On a ±34.47 kPa instrument, 0.3% of full scale works out to about ±0.10 kPa, and that band is the same whether you're reading 30 kPa or 1 kPa.
That's a small error on a high reading and a much bigger share of a low one. At an appliance regulator set to around 1 kPa, ±0.10 kPa is roughly a 10% band. For setting and checking appliance pressures that's usually workable, but it's worth knowing when a reading sits right on the edge of a manufacturer's tolerance. In that situation, take the reading more than once, use the record function to check it's stable, and if it's critical, confirm it with a lower-range instrument.
Connecting it properly
Most bad readings come from the connection, not the gauge. Before reading anything:
- Zero it at atmosphere with the hose disconnected, after it has settled to site temperature.
- Use the right adaptor for the test point. We stock brass test point adaptors in common thread combinations, from Rp1/2” female x R1/2” male to Rp3/8” female x R3/8” male, plus a 1/8” BSP regulator test point.
- For tightness testing at the meter, a manometer test tee (Plumtest 550258) lets you connect the manometer and bellows at one fitting, so you can pressurise and watch the line from the same point.
- Check the hose for kinks and leaks before blaming the installation for a falling reading.
- Refit the test point screw and leak-check it when you're done. A test point left loose is a leak you created.
Using the record function on a pressure drop test
For tightness testing, the record function earns its keep. Bring the section to test pressure, let it stabilise, then start recording and leave it for the period required. Max, min and average tell you whether the pressure held or crept down, without someone staring at the screen. The test pressure and duration come from AS/NZS 5601.1 and your state's gas technical regulator, not from the instrument, so check the current requirement for the type of installation you're working on.
The 137 kPa limit
The listing gives 137 kPa as the maximum pressure before failure. That's well above appliance and low-pressure consumer pressures, but it's below the pressures you'll find upstream of a first-stage LPG regulator or on elevated supplies. Never connect this gauge before the regulator. If you're setting up an LPG system, our guides on single vs dual stage LPG regulators explain where each pressure zone sits.
Calibration
A digital manometer drifts like any instrument. If you rely on it for compliance testing, check what your state regulator expects for calibration intervals and records, and keep the calibration certificate with your test records. A cheap spot-check is to compare it with a second, known-good instrument on the same test point.
Frequently Asked Questions
Is a ±34.47 kPa manometer suitable for natural gas and LPG appliances?
Yes for appliance and low-pressure consumer piping work, which sits well inside the range. Keep it downstream of regulators, as the listed maximum before failure is 137 kPa.
How accurate is it at around 1 kPa?
The accuracy is ±0.3% of full scale, about ±0.10 kPa across the whole range. At about 1 kPa that's roughly a 10% band, so take repeat readings when a result is close to a tolerance limit.
What do I need to connect it to a test point?
A hose and the right brass test point adaptor for the thread, or a manometer test tee if you're pressurising and monitoring a line at the meter.
Does it need calibrating?
Calibration requirements for compliance testing vary by state, so check with your gas technical regulator and keep the calibration certificate with your test records.