Dab K Twin Inpeller

The DAB K Twin-Impeller is a cast iron centrifugal pump that runs two impellers in series to produce far more head than a single-impeller pump of the same power. The K 35/100 delivers up to 7.2 m³/h against 38.5 metres of head on 1.1 kW — roughly double the flow of a domestic jet pump of comparable size. It is built for pressurisation, pressure vessel filling, sprinkler systems and general water supply.

What twin impellers actually do

A single impeller can only generate so much pressure before it starts to slip — push it harder and it simply churns. The way to get more head without a bigger motor is to stage the pump: send the output of the first impeller straight into the inlet of a second, so each one adds its own lift.

That is what the K series does. The result is a pump that produces 38.5 metres of head from 1.1 kW while still moving 7.2 m³/h — a combination a single-impeller pump of the same power cannot reach. It also gives the range an unusually flat curve through the mid-band: the K 35/100 is still delivering 35 m at 2.4 m³/h and 32 m at 3.6 m³/h, so pressure at the outlet stays consistent as demand rises and falls.

This pump is not self-priming. It must be installed with a flooded suction — the water source at or above pump level — and the casing filled before starting. If your water sits below the pump and has to be sucked up, you need a self-priming jet pump such as the DAB Jetcom instead. This is the single most common mistake made when choosing between the two.

K Twin-Impeller — models and specifications

Supply 1 × 220–240 V ~ 50 Hz, capacitor 25 µF / 450 V permanently fitted. Suction port 1½" G, discharge port 1" G. Unit weight 22 kg.

Performance table — head against flow

Find the flow you need along the top, then read across for the head the pump still delivers at that flow.

Head in metres. Performance curves are based on kinematic viscosity of 1 mm²/s and density of 1000 kg/m³, with curve tolerance to ISO 9906.

Note the shape of this curve. The K 35/100 holds 35 m all the way out to 2.4 m³/h and 32 m at 3.6 m³/h, then falls away sharply past 4.8 m³/h. That flat mid-band is exactly what you want for pressure boosting — consistent pressure whether one tap is open or three. Design inside 4.8 m³/h and the pump behaves predictably; push it toward 7.2 and head collapses.

How to size the K 35/100

1. Confirm you have a flooded suction. The supply must sit at or above pump level. If not, choose a jet pump instead.
2. Measure the delivery height from the pump to the highest outlet or tank inlet.
3. Add the pressure you want at the outlet. 20 m (2 bar) gives a comfortable shower; a sprinkler system usually wants 25–30 m.
4. Add friction loss in the delivery pipe. Use 32 mm pipe or larger on any long run; undersized pipe is the usual reason a good pump disappoints.
5. Total it for your total dynamic head.
6. Work out peak flow. One shower is roughly 0.6 m³/h; a household with several outlets open, 1.8–2.4 m³/h; a sprinkler zone, 2–4 m³/h depending on head count.
7. Check the performance table at that flow and confirm the head still exceeds your total, with margin.

A worked example: a house boosting from a ground-level storage tank to a first-floor bathroom 6 m up, wanting 2 bar at the shower, with 5 m of pipe friction. Total head = 6 + 20 + 5 = 31 m. At a peak demand of 3.6 m³/h the K 35/100 delivers 32 m — workable but tight. At a more realistic 2.4 m³/h it delivers 35 m, with comfortable margin.

Manual or Auto — which version

The M version is the bare pump. It runs whenever it has power, so a booster installation needs a pressure switch and pressure vessel wired in to cycle it on demand.

The Auto version comes with an automatic pump controller fitted to the discharge, which does that job in one unit:

• Starts the pump the instant a tap or outlet is opened
• Stops it once flow ceases
• Shuts the pump down if the water supply runs dry, protecting the seal and motor
• Includes a non-return valve to prevent backflow
• Removes the need for a pressure vessel and separate pressure switch
• LED indication of power, running and fault status

Note the K 35/100's starting current of 33 A. It is brief, but it matters on a weak supply or a long cable run — size the circuit and cable accordingly rather than assuming the 7.1 A running figure is the whole story.

Construction and materials

The cast iron body is the K series' defining feature against a plastic-bodied domestic pump. It is heavier — 22 kg against the 8 to 10 kg of a jet pump — but it runs quieter, absorbs vibration instead of transmitting it, and tolerates continuous duty far better. In a pump room or a pressurisation set that cycles all day, that difference is what you are paying for.

Operating limits

Typical applications

• Pressurisation units in domestic, civil and industrial water systems
• Filling pressure vessels and header tanks
• Sprinkler and irrigation systems needing steady pressure across multiple heads
• Tank-to-house boosting where the tank sits at or above pump level
• General water supply in commercial and light industrial installations
• Continuous-duty service where a plastic-bodied domestic pump would not last

Frequently asked questions

Pricing

Available as the bare pump (M) or complete with an automatic pump controller (Auto). Prices include VAT and are subject to change; the online store always carries the current price.

Related ranges

• DAB Jetcom Self-Priming Centrifugal Electric Pumps 230V — self-priming jet pump for water sitting below the pump
• All DAB Pumps — the full DAB range
• Leo Submersible Borehole Pump Series — for drawing from depth
• Solar Pump Range — off-grid borehole and surface pumping