Best Backflow Test Kit (2026): Digital and Analog Picks

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Quick answer from a licensed plumber: Buy the Arbiter Mako MK5 if your authority requires a USC approved kit: it is the only kit on the USC Foundation’s approved field test kit list we read, and Arbiter lists ±0.1 psid accuracy from 0 to 15 psid. The 3-valve Mako MK3 is the same digital gauge for 3-valve procedures. For a mechanical kit, the Watts TK-9A. Your local authority decides which kits and which tester certifications it accepts.

Our pick for most certified testers: the Arbiter Mako MK5 digital 5-valve test kit. Check the Arbiter Mako MK5 on Amazon

A backflow test kit is the gauge a certified tester uses to prove a backflow assembly works: it reads the pressure difference across each check valve and the point where a relief valve or air inlet opens. This page compares three kits, two digital and one analog, that were sold by Amazon.com or by the maker’s own Amazon store when we checked. The specs come from the makers, and the approval and certification facts come from the USC Foundation for Cross-Connection Control and Hydraulic Research and ASSE International.

Backflow Test Kits Compared

Kit	Gauge	Valves	Accuracy (maker)	On a USC list we read?	Sold by
Arbiter Mako MK5	Digital	5	±0.1 psid, 0 to 15 psid	Yes: approved field test kit list	Arbiter’s Amazon store
Arbiter Mako MK3	Digital	3	±0.1 psid, 0 to 15 psid	No	Arbiter’s Amazon store
Watts TK-9A	Analog, 4-1/2 in.	3	±2%	No	Amazon.com

Accuracy from Arbiter’s manuals and product pages and Watts’ ES-TK-9A. USC column: the approved field test kit list (December 10, 2019) and the Ninth Edition acceptable gages list (January 31, 2025). Each linked kit was in stock on October 6, 2026; the Arbiter kits were sold by Arbiter’s own Amazon store.

What a Field Test Kit Has to Do

The USC Foundation describes a field test kit as a differential pressure gauge: it measures the difference between two pressure points, such as the drop across the check valves inside an assembly. A tester uses it on the four testable types the USC tester course covers: pressure vacuum breakers, spill-resistant vacuum breakers, double checks and reduced pressure principle assemblies.

Digital or analog. The Arbiter Mako is digital, with ±0.1 psid accuracy from 0 to 15 psid per Arbiter. The Watts kit uses a 4-1/2-inch mechanical gauge at ±2 percent.
3-valve or 5-valve. Arbiter’s MK3 has high, low and bypass valves; its MK5 adds high and low bleed ports, and each matches an accepted configuration in the USC Manual 10. The analog Watts kit has three valves. Buy the layout your required test procedure uses.
Approval. The USC Foundation approves field test kits against a standard in Chapter 10.2 of its Tenth Edition manual. It also says the local administrative authority decides whether a USC approved kit is required.

Calibration

Arbiter says every backflow test kit, its own included, must have its accuracy verified against a lab standard, and recommends doing it every year at a lab with a current certified reference standard. Its MK5 accuracy table assumes calibration within the past 12 months. Buffalo Backflow’s cut sheet says most regulations require a kit to be calibrated and certified at least once a year. Plumber’s note: keep the calibration certificate with the kit so you can show it when someone asks.

Best Digital Test Kit

Arbiter Mako MK5 Digital 5-Valve Backflow Test Kit

Digital differential gauge · 5-valve (high, low, bypass, high bleed, low bleed) · ±0.1 psid from 0 to 15 psid when calibrated within 12 months · stores six captured readings · Bluetooth · IP57 · 4 AA batteries · 175 psi max inlet, 140°F max water · 5-year gauge warranty from the date of manufacture · sold by Arbiter’s Amazon store

The MK5 is the only kit on the USC Foundation’s List of Approved Field Test Kits, the December 10, 2019 version the Foundation links from its site. That list covers kits that passed the Foundation’s field test kit standard in Chapter 10.2 of its Tenth Edition manual. Arbiter’s manual says the MK5 can run all standard test procedures, including those from USC, ABPA, NEWWA, AWWA, UF TREEO and ASSE, and its five ports match a 5-valve configuration from the USC Manual 10.

The digital parts are what change the test. Arbiter’s manual lists ±0.1 psid accuracy from 0 to 15 psid at 70°F, provided the gauge has been calibrated in the past 12 months and runs firmware version 12 or later. A capture button stores up to six readings, which Arbiter says lets you watch the assembly instead of the gauge when a relief valve or air inlet opens. A rate-of-change graph shows when the reading is stable. Arbiter says its hoses use materials suitable for potable water under NSF 61 and FDA guidelines and carry a 40-micron filter, and that freezing the gauge with water inside voids the warranty. Arbiter’s manual counts the five-year warranty from the date of manufacture and limits it to the original purchaser.

The only kit on the USC approved field test kit list we read
±0.1 psid from 0 to 15 psid, per Arbiter
Captures six readings; Bluetooth to a phone
5-year gauge warranty, counted from the date of manufacture

Accessories carry a 1-year warranty, consumables none
Freezing with water inside voids the warranty
Runs on batteries
USC approval holds only with Arbiter’s own hoses and valves

Verdict: The kit to buy if your authority requires a USC approved kit, or if you want digital readings and stored values.

Check the Arbiter Mako MK5 on Amazon

Best 3-Valve Digital Kit

Arbiter Mako MK3 Digital 3-Valve Backflow Test Kit

Digital differential gauge · 3-valve (high, low, bypass) · ±0.1 psid from 0 to 15 psid · captured readings · Bluetooth · IP57 · 4 AA batteries · 175 psi max inlet, 140°F max water · 5-year gauge warranty from the date of manufacture · sold by Arbiter’s Amazon store

The MK3 is the same Mako gauge with three valves: high pressure, low pressure and bypass. Arbiter’s manual says its flow layout is an accepted 3-valve configuration in the USC Manual 10, and that the Mako can run the standard procedures from USC, ABPA, NEWWA, AWWA, UF TREEO and ASSE. The MK5 adds the two bleed ports.

Arbiter lists the same ±0.1 psid accuracy from 0 to 15 psid, IP57 rating, four AA batteries, 175 psi inlet and 140°F water limits, and 5-year gauge warranty, counted from the date of manufacture, for the MK3. The USC approved field test kit list we read names only the MK5, so check with your authority before you buy the MK3 if it requires a USC approved kit.

Same digital gauge, display and capture button as the MK5
Accepted 3-valve layout in the USC Manual 10, per Arbiter
Fewer ports and hoses to manage
5-year gauge warranty, counted from the date of manufacture

Not on the USC approved field test kit list we read
No bleed ports
Freezing with water inside voids the warranty

Verdict: The digital kit for testers whose authority uses a 3-valve procedure and does not require a USC approved kit.

Check the Arbiter Mako MK3 on Amazon

Best Analog Kit from a Backflow Maker

Watts TK-9A Backflow Preventer Test Kit

Analog 4-1/2 in. dual-scale gauge, 0 to 15 psi and 0 to 1 bar · ±2% accuracy · 3 valves: two ball valves and one needle valve · three 3 ft hoses · adapters for testable assemblies · 175 psi max working pressure, 210°F max · carrying case · sold by Amazon.com

Watts makes backflow assemblies as well as the TK-9A, and it says the kit tests all reduced pressure zone assemblies, double checks, pressure vacuum breakers and spill-resistant vacuum breakers to USC and ASSE 5000 standards. It is a mechanical kit: a 4-1/2-inch dual-scale gauge reading 0 to 15 psi, two ball valves for on and off and a needle valve for metering, with an accuracy of ±2 percent.

Watts includes three 3-foot hoses with swivel couplings, adapter fittings, a securing strap, a moisture-resistant manual and a shock-resistant case, and rates the kit to 175 psi and 210°F. We did not find the TK-9A on either USC list we read: the approved field test kit list or the Ninth Edition acceptable gages list, which names the Watts TKDR, TKDP and TK99D. Ask your authority whether it accepts the TK-9A.

Watts says it tests RPZ, double check, PVB and SVB assemblies
No batteries
Rated to 210°F, per Watts
Hoses, adapters and case included

±2% accuracy, against ±0.1 psid on the Mako from 0 to 15 psid
Not on either USC list we read
Watts’ spec sheet does not mention a calibration certificate

Verdict: A mechanical kit from a backflow maker, if your authority accepts it.

Check the Watts TK-9A on Amazon

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What About the Buffalo Backflow BBI-TK9S?

Buffalo Backflow’s BBI-TK9S is another analog kit. Its cut sheet lists a 4-1/2-inch dual-scale gauge from 0 to 15 psid at ±2 percent of full scale, two ball valves and a needle valve, and an in-line 0 to 200 psi gauge for line pressure. Buffalo Backflow says the kit ships with a NIST traceable certification good for one year and lists a 6-year warranty. Its Amazon listing read currently unavailable when we checked, so we do not link it. We did not find it on either USC list we read.

Tester Certification

The kit does not make you a tester. ASSE International’s 5110 Backflow Prevention Assembly Tester certification requires five years of documented field experience in plumbing, mechanical, fire protection, lawn irrigation or a related field, a 40-hour course, a 100-question exam passed at 70 percent or higher, and a practical exam on ASSE 1013, 1015, 1020 and 1056 assemblies. It runs for three years. ASSE says the test procedure used in the practical exam is set by the local authority, and that the USC Tenth Edition procedure is common in California. The USC Foundation runs its own 5-day tester course on the same four assembly types.

Your state or water authority decides which certification it accepts. If you are looking for the assemblies themselves, our backflow preventer guide compares PVB, RPZ and double check assemblies.

Before You Buy

Ask what your authority accepts. Some require a USC approved kit; the USC Foundation leaves that call to the local authority.
Match the procedure. A 3-valve or 5-valve kit, to match the test procedure you will file under.
Use the maker’s hoses. The USC Foundation says other hoses or needle valves void a kit’s USC approval, and Arbiter says hoses not supplied by Arbiter void its warranty.
Plan the calibration. Yearly, per Arbiter and Buffalo Backflow.
Keep it from freezing. Arbiter says a Mako frozen with water inside is not covered by warranty.

FAQ

What does a backflow test kit measure?

Pressure difference. The USC Foundation describes a field test kit as a differential pressure gauge that measures the difference between two pressure points, such as the pressure drop across the check valves inside an assembly.

Do I need a 3-valve or a 5-valve test kit?

Match the test procedure your authority requires. Arbiter says its MK3 matches an accepted 3-valve configuration and its MK5 an accepted 5-valve configuration in the USC Manual 10, and Watts says its 3-valve TK-9A tests RPZ, double check, PVB and SVB assemblies.

Does my test kit have to be USC approved?

Only if your local authority says so. The USC Foundation says it is the decision of the administrative authority whether a USC approved field test kit is required, and its approval holds only with the needle valves and hoses the maker supplied.

How often does a backflow test kit need calibration?

Arbiter recommends having a Mako verified against a lab standard every year, and its accuracy figures assume calibration within the past 12 months. Buffalo Backflow says most regulations require a kit to be calibrated and certified at least once a year. Check your authority’s rule.

How do I become a certified backflow tester?

Your jurisdiction sets the path. ASSE International’s 5110 tester certification requires five years of related field experience, a 40-hour course, a 100-question written exam and a practical exam on ASSE 1013, 1015, 1020 and 1056 assemblies, and it runs for three years. The USC Foundation also runs a 5-day tester training course.

Why Trust Plumbing Picks

Plumbing Picks is written by a licensed Georgia journeyman plumber. Every spec here comes from the maker documents and the USC Foundation and ASSE pages linked below, or from the Amazon listings we link; nothing comes from hands-on testing. On October 6, 2026, every linked listing was in stock and sold by Amazon.com, or by the maker’s own Amazon store where we say so. If you buy through a link we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.

Sources

Bottom Line

Start with your authority’s rules: which test procedure, whether the kit must be USC approved, and how often it must be calibrated. The Arbiter Mako MK5 is the one kit here on the USC approved field test kit list. The Mako MK3 suits 3-valve procedures, and the Watts TK-9A is the mechanical option. Calibrate it every year and keep the maker’s hoses on it.