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Deep well pump buying guide

Updated: 22 October 2026

If the water in a dry week sits too deep for a surface pump, a deep well pump buying guide starts with the hole, not the watts. Maximum head and maximum flow on an amazon.co.uk title are opposite ends of a curve, so they are not one working point. The seven kept listings sit on the [deep well pump comparison](/hub/garden-watering/deep-well-pump). Peter F., editor for DIY & tools, updated this on 22 October 2026. We did not lab-test them. A qualifying purchase can earn a commission at no extra cost to you. Finish with the flow you still have at your real head, in a body that passes the hole.

If the water in a dry week sits too deep for a surface pump, a deep well pump buying guide starts with the hole, not the watts.

Our top picks

Draper Draper 98921 well pump

Best overall

Draper Draper 98921 well pump
9.4/10about £124.13
View offer
Generic IBO SDM 24 borehole pump

Alternative

Generic IBO SDM 24 borehole pump
7.2/10about £227.95
View offer
Generic 3 inch SKM 60 m pump

Best value

Generic 3 inch SKM 60 m pump
6.9/10about £180.45
View offer
On this page
  1. 1.Measure the hole and the pumping level
  2. 2.Turn lift and pressure into head
  3. 3.Read flow at that head, not at zero head
  4. 4.Water, cable, and the licence line

Measure the hole and the pumping level

Measure the dry-spell pumping level, not the wet-day water and not the depth of the hole alone, and measure the smallest internal diameter, including the cable, the joint and any scale. The Draper 98921 is 33 × 24 × 18 cm, so it will not enter a 3 inch or 4 inch casing. The SDM 24 and the STM 28 are 75 mm and already ask for 85 mm inside. The 3 inch SKM is also 75 mm and only says “minimum 3 inch wells”. The shapes are separated on the borehole or wide well page.

Turn lift and pressure into head

Total head is the lift from the pumping level, any extra height to a tank or tap, friction in the pipe, and the pressure you still want. A rule of thumb from UK pump sellers, not a test of these ASINs, is about 10 metres of head for each bar. Two bar at a garden tap is about 20 metres before friction is added. AES Rewinds works an example of a 40 metre pumping level plus a tank 10 metres up and lands at about 55 to 60 metres before a curve. The Draper’s own headline is 40 metres, so the example already asks that pump for more than its catalogue maximum. Write your total in metres before you compare a 107 metre headline with a 60 metre one.
Draper Draper 98921 well pump

Testsieger

Draper Draper 98921 well pump
9.4/10about £124.13
View offer

Read flow at that head, not at zero head

Maximum flow is the figure at little or no head. Maximum head is the figure when flow has fallen away. The 4 inch SKM prints 107 metres and 3000 litres an hour as those two ends, not as one duty. No file in this set includes the middle of the curve. If the hole makes 10 litres a minute and the title talks about 70 or 100, the hole wins. Only two listings write a starts limit: the SDM 24 at 20 an hour, and the STM 28 at 30. The best deep well pump page applies that limit to each kept model.

Water, cable, and the licence line

The SKM peripherals ban solids and abrasive particles. They are clean-water pumps. The SDM 24, STM 24 and STM 28 claim increased resistance to sand and give no grams-per-cubic-metre limit, so you cannot design to that claim. The 3 inch SKM says 20 metres in the title and 15 metres in a later bullet. The SDM 24 and the STM 28 say 20 metres and a plug in the title, and the technical data also allows 1.5 metres. A 1.5 metre tail is an appliance lead, not a drop cable. No file states a BS 1363 plug. In England and Wales, more than 20 cubic metres a day is the point at which a licence is likely. Scotland’s general binding rule sits under 10 cubic metres a day. If the pumping level stays inside about 7 to 8 metres of a surface pump all year, use the garden pump or deep well pump page.

Common questions

What do I measure before I look at watts?
Measure the dry-spell pumping level and the smallest internal diameter, including room for the cable and the joint. Watts do not shrink a 24 cm Draper into a 4 inch casing, and they do not move a surface pump’s suction limit. A wet-day water level will flatter the hole.
Why is flow weak when the title promised a huge head?
The huge head and the huge flow are opposite ends of a curve, and these listings do not print the middle. A pump advertised at 107 metres and 3000 litres an hour is not offering both at once. At the head you need, flow is lower, and borehole yield can cut it further.
Will a 75 mm pump fit a 3 inch casing?
Not on the words “3 inch”. AES Rewinds puts a typical pump for a 3 inch hole at about 68 mm outside or under. The SDM 24 and the STM 28 are 75 mm and ask for 85 mm inside. The 3 inch SKM is 75 mm and only says minimum 3 inch wells. Measure the real inside.
How many metres of head is 1 bar at the tap?
About 10 metres of head per bar is the rule of thumb UK pump sellers use, and it is not a test of these pumps. Two bar at a tap is about 20 metres before lift and pipe friction. AES’s example of a 40 metre pumping level plus a tank 10 metres up is about 55 to 60 metres. That example is theirs.
Does garden watering skip the abstraction licence?
No. The test is daily volume, not whether the water ends up on a border. In England and Wales the licence line is more than 20 cubic metres a day. Scotland and Northern Ireland use a lower band, under 10 cubic metres, with different rules above that. A garden hose is not an exemption.
Which cable length is in the box when the listing says 20 m or 1.5 m?
The files do not say. On the SDM 24 and the STM 28 the title says 20 metres and a plug, and the technical data also says 1.5 metres. On the 3 inch SKM the title says 20 metres and a later bullet says 15 metres. A 1.5 metre lead cannot hang a pump tens of metres down. Confirm the cord, and do not assume a BS 1363 plug.

Related pages

How to install a deep well pump

Deep well pump

Best deep well pump: match the hole, then the head

Borehole pump or well pump: width against the bore

Garden pump or deep well pump: where suction stops

Sources

Public UK sources from the research digest. Shelf prices, heads, flows and conflicts are from the amazon.co.uk saved listings in this category, not a live re-check on 21 October 2026.

  1. GOV.UK — check if you need a licence to abstract water (retrieved 21.10.2026)
  2. Water Resources Act 1991, section 198 (retrieved 21.10.2026)
  3. British Geological Survey — drilling legislation and obligations (retrieved 21.10.2026)
  4. Natural Resources Wales — water abstraction or impoundment licence (retrieved 21.10.2026)
  5. SEPA — abstraction under 10 cubic metres a day (retrieved 21.10.2026)
  6. DAERA — applying to abstract or impound water (retrieved 21.10.2026)
  7. AES Rewinds — choosing the right well pump (retrieved 21.10.2026)
  8. Drinking Water Inspectorate — single dwelling supplies (retrieved 21.10.2026)