Ebara BEST 2 Submersible Sump Pump

The Ebara BEST 2 is a portable stainless steel sump pump for clean and dirty water. Ebara puts the range on seepage water, on emptying basements, garages and cellars, and on draining small and medium-sized construction sites. It is built entirely in AISI 304 with a double mechanical seal, which is what makes it worth more than a pressed-steel builder's pump on a site that is going to run it every week for a year.

Get the frame right first. Ebara publishes BEST 2-5 as one range, and the figures on its own product page cover all four sizes together, 1.2–21.6 m³/h and 2.9–18.4 m of head. Those are not the BEST 2's numbers. The BEST 2 is the 0.55 kW frame at the bottom of that spread, and its own curve stops at 15.6 m³/h and 13.1 m. BEST 3 is 0.75 kW, BEST 4 is 1.1 kW and BEST 5 is 1.5 kW and three-phase only. If you size against the range headline and order a BEST 2, you will be short of head.

The other figure to read carefully is temperature. The BEST 2-5 range is rated to +35°C. Ebara's own BEST ONE, a quarter of the power, takes +50°C, so the bigger pump here is the one with the tighter temperature limit. Warm process water, boiler blowdown or anything coming off a wash plant will take you past it. Tell us the liquid temperature and we will check it before you buy.

A 10 mm solids passage is what it says. Suspended particles up to 10 mm go through the impeller. Rag, wipes and fibre will still wrap it, because an open centrifugal impeller has no cutter and nothing to clear itself with. If the sump takes anything off a WC or a macerator, this is the wrong pump and we will tell you so rather than sell you one.

Where the BEST 2 earns its place is the seal arrangement. Two mechanical seals running in an oil chamber, rather than one seal and a lip, is the difference between a pump that survives a gritty sump and one you rebuild each season. The weak point in almost any submersible is the seal, and Ebara has spent the cost here rather than on the casing.

The BEST 2 pulls water through a stainless strainer in the base, throws it out through an open centrifugal impeller of 112 mm diameter, and discharges through a G 1½ connection to UNI ISO 228. The motor is a submersible dry type, two pole, running at about 2,800 rpm at 50 Hz and rated 0.55 kW. Ebara measures the curves to ISO 9906:2012 Grade 3B with clean water at 20°C and a kinematic viscosity of 1 cSt.

Two seals and an oil chamber

The shaft passes through two mechanical seals with an oil chamber between them. The pump-side seal uses silicon carbide with NBR elastomers, the motor-side seal carbon and ceramic with NBR. Between them sits 180 cc of white mineral oil, Esso Marcol 172, which lubricates and cools both sets of faces.

That is a genuine double seal, and it matters in a sump full of grit. If the pump-side face wears, the oil chamber gives you a second barrier before water reaches the windings, and oil in the chamber going milky is the early warning you get before a motor failure. Run the pump dry and you lose the lubricating film on the faces, which is the fastest way to kill it.

Reading the type key

Ebara's own worked example is BEST 3 M A. The model number gives the frame, 2 to 5. M means single phase only, and A means the pump is supplied with a float switch. So a BEST 2 M A is a single-phase 0.55 kW pump with a float, and a plain BEST 2 is the three-phase build. If you are matching an existing unit, send us that designation and the serial number off the nameplate.

Certification

TÜV SÜD Product Service GmbH issued GS mark certificate Z1A 015912 0052 to Ebara Pumps Europe S.p.A. for the range. The certificate lists the BEST 2 builds as BEST/A 2, BEST/A 2M and BEST/A 2M A, tested to EN 60335-1:2012/A15:2021, EN 60335-2-41:2021/A11:2021, EN 62233:2008 and AfPS GS 2019:01 PAK. It runs to 6 February 2029. The motor is IP68 with class F insulation.