How to choose a compressor water separator
Updated: October 2026
You have a 24 or 50 litre compressor in a UK garage, and every amazon.co.uk card seems to say 1/4 inch in a different way. How to choose a compressor water separator, in this set of six, is a fixed order: the thread that is actually printed, the stated pressure against the cut-out, flow only where a number exists, then what the bowl removes and whether you can drain it. The [water separator comparison](/hub/compressors/water-separator) lines the six prices up. This page names no top pick. A qualifying purchase from our links can earn us a commission at no extra cost to you. Listings were read on 15 October 2026. We have not lab-tested a bowl.
You have a 24 or 50 litre compressor in a UK garage, and every amazon.co.uk card seems to say 1/4 inch in a different way.
You have a 24 or 50 litre compressor in a UK garage, and every amazon.co.uk card seems to say 1/4 inch in a different way. How to choose a compressor water separator, in this set of six, is a fixed order: the thread that is actually printed, the stated pressure against the cut-out, flow only where a number exists, then what the bowl removes and whether you can drain it. The water separator comparison lines the six prices up. This page names no top pick. A qualifying purchase from our links can earn us a commission at no extra cost to you. Listings were read on 15 October 2026. We have not lab-tested a bowl.
Our top picks
| Badge | Product | Thread as printed | Stated maximum pressure | Drain | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  CYTGOUPER CYTGOUPER AF2000-02 | G1/4 | 0.05–0.85 MPa | Sprung valve in a UK review | 9.4 | about £10.69 | View offer |
| Alternative |  Tiardey Tiardey TD-AF002 | NPT in the title; G1/4 in a bullet | 90 psi | Release valve | 8.8 | about £8.99 | View offer |
 nutmanel nutmanel 003 | 1/4 inch; G, R or NPT not stated | 1.0 MPa | n/a | 8.6 | about £12.34 | View offer |
On this page
Match the thread before the port size
UK airlines normally use BSP. Parallel BSP is often marked G, and taper BSP is often marked R. NPT is a 60-degree American taper, and it is not a substitute for 55-degree BSP. A card that only says 1/4 inch has not told you which standard is in the box.
Tiardey, at about £8.99 for two, prints NPT in the title and G1/4 in a bullet. CYTGOUPER prints G1/4, but a UK review reports 1/8 inch outlets. PRITOK, nutmanel, and Hakeeta leave G, R, and NPT blank. PCL says Standard and XF-Euro do not interchange, and Noosverl’s German Type line is the European profile.
Set the stated pressure against the cut-out
Set the printed maximum against the pressure where your compressor cuts out, and keep a margin rather than running the bowl at its ceiling. Tiardey prints 90 psi. If your cut-out sits above that, this pack is the wrong trap. CYTGOUPER prints 0.05–0.85 MPa. nutmanel and Noosverl print 1.0 MPa. Hakeeta prints 1000 kPa, the same 10 bar, on the only 1/2 inch body, at about £29.11.
PRITOK, at about £11.99, prints 9.9 kilopascal, about 0.1 bar. That is not a cut-out, and the regulator in the title does not repair it. None of the six states UKCA or CE. A single job gets a listing on the best water separator page.
Read flow only where it is printed
Tanair’s point is the one most port-size shopping ignores: connection size is not capacity. Only CYTGOUPER prints a flow, 750 L/min, beside 5 μm. That is a listing claim, not a test we ran, and 4.7 from three reviews does not make it a measured delivery on your 24 litre compressor. The other five leave flow blank. Do not invent a litres-per-minute figure from 1/4 inch or from Hakeeta’s 1/2 inch body. Atlas Copco UK’s 80–90 percent band is for a correctly sized trap, not a measurement of any ASIN here.
See what the bowl removes, and whether you can drain it
BCAS describes a separator as a reducer of liquid, usually oil and water mixed, where it is fitted. It is not a dryer. Atlas Copco UK says liquid can fall into the bowl while water vapour stays in the air. CYTGOUPER and nutmanel print 5 μm. That is not the 0.5 micron stage Spray Guns Direct uses for spraying. None of the six prints a dew point.
Count a regulator only when the listing includes one. nutmanel’s title says pressure reducer. Hakeeta’s style line says filter regulator. Tiardey has a release valve, PRITOK’s title says hand drain, and a UK review of CYTGOUPER describes a sprung valve. nutmanel and Hakeeta do not describe a drain. A full bowl stops separating, and the separator does not empty the receiver.
The order, then the listing
If the printed thread does not match the outlet, stop before price. If the stated maximum sits under the cut-out, skip that listing. If the card has no flow, leave the line empty. If you cannot see a drain, do not invent one. Which listing fits one job is a different page. Fitting the unit you have already matched is a different page again.
Common questions
Is a 1/4 inch water separator the same as 1/4 inch BSP?
No. 1/4 inch here is a nominal size, not a thread standard. BSP is the usual UK form, often marked G when parallel and R when taper. NPT will not seal on BSP. Tiardey’s title says NPT and a bullet says G1/4, so that pack disagrees with itself. A bare 1/4 inch on nutmanel, PRITOK, or Noosverl still leaves the standard unknown.
Can I screw an NPT trap into a BSP compressor outlet?
You should not. NPT is a 60-degree taper and BSP is 55 degrees, so the threads do not seal. PTFE tape fills small gaps on a matching taper. It does not convert one standard into the other. If the title and a bullet disagree, as on the Tiardey pack, confirm the thread before you load the joint.
Should the stated maximum pressure sit above the compressor cut-out?
Yes. The printed ceiling has to clear the cut-out, with room to spare. Tiardey’s 90 psi fails that test if your cut-out is higher. nutmanel, Noosverl, and Hakeeta print the equivalent of 10 bar. PRITOK’s 9.9 kPa is about 0.1 bar and is not a working maximum you can compare with a cut-out.
Does a bigger port mean the trap can pass more air?
Not by itself. Tanair states that connection size is not capacity. Only CYTGOUPER prints a flow, 750 L/min. Hakeeta is the 1/2 inch body and prints no flow. Do not invent a litres-per-minute figure for the other five from the port size on the title.
What is the difference between a water trap and a filter regulator?
A water trap knocks liquid out at that point in the line. A filter regulator adds a pressure reducer, and sometimes a gauge. nutmanel’s title says pressure reducer, and Hakeeta’s style line says filter regulator. Tiardey is traps only. Noosverl is a separator with couplings. PRITOK claims a regulator, but its pressure field is not usable.
Do German Type couplings fit PCL Standard couplings?
Do not assume they do. PCL says Standard and XF-Euro profiles do not interchange. Noosverl’s German Type line points at the European profile, not at PCL Standard. If your hose already uses PCL Standard couplings, this box is the wrong match even if both sides are called 1/4 inch.
Related pages
Sources
Public UK sources used for this comparison. Listing prices, stars, and review counts are from amazon.co.uk on 15 October 2026.
- Atlas Copco UK — moisture trap (retrieved 15 October 2026)
- BCAS BPG 104 — filtration and drying of compressed air (retrieved 15 October 2026)
- Tanair — water traps (retrieved 15 October 2026)
- HSE INDG178 — written schemes of examination (retrieved 15 October 2026)
- HSE INDG261 — compressed air safety (retrieved 15 October 2026)
- GOV.UK — Pressure Equipment (Safety) Regulations 2016 (retrieved 15 October 2026)
- PCL — Standard and XF-Euro coupling profiles (retrieved 15 October 2026)
- Spray Guns Direct — filtering compressed air for spray painting (retrieved 15 October 2026)
- BCAS — condensate fact sheet (retrieved 15 October 2026)