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Borehole pump or well pump

Updated: 22 October 2026

A borehole pump and a wide well pump can both say “deep well” on an amazon.co.uk title and still be the wrong shape for each other. The Draper in this set is 24 cm across. The slim IBO bodies are 75 mm. The dimensions come from the seven listings in 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 measure your casing or lab-test the pumps. A qualifying purchase can earn a commission at no extra cost to you. Head stays on the [deep well pump buying guide](/hub/garden-watering/deep-well-pump/sub/deep-well-pump-buying-guide).

A borehole pump and a wide well pump can both say “deep well” on an amazon.co.uk title and still be the wrong shape for each other. The Draper in this set is 24 cm across. The slim IBO bodies are 75 mm.

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.Two shapes, one category name
  2. 2.Nominal inches against the files
  3. 3.A slim pump in a wide hole
  4. 4.When each shape

Two shapes, one category name

Flood & Water Pumps puts the split plainly. A well pump is the wider, higher-flow body. A borehole pump is the slim, high-pressure body. The Draper 98921 is 33 × 24 × 18 cm, rated at 40 metres maximum head and 5460 litres an hour, with a float. It will not pass a 3 inch or a 4 inch casing. The 3 inch SKM, the SDM 24, the STM 24 and the STM 28 are 75 mm outside. The 4 inch SKM is 98 mm outside. The Trotec TDP 5500 E is 10 × 10 × 78 cm, with only 20 metres of headline head. The SDM 24 and the STM 28 say the minimum internal diameter is 85 mm. The STM 24 does not state a minimum bore, so you cannot give it their 85 mm line. If the body may jam, the lowering sequence lives on the installation page.

Nominal inches against the files

“3 inch” on a title is not the hole. A nominal 3 inch bore is about 76 mm, which leaves almost nothing around a 75 mm pump once the cable and the joint are in the gap. AES Rewinds puts a typical pump for a 3 inch hole at or under about 68 mm outside. Every 75 mm listing here is wider than that typical envelope. The SDM 24 and the STM 28 ask for 85 mm inside. The 3 inch SKM says “minimum 3 inch wells” and is still 75 mm. A 4 inch hole is nominally about 102 mm. AES’s typical pump for that hole is at or under about 96 mm outside. The 4 inch SKM is already 98 mm before the cable, while its bullet says minimum 4 inch wells. Gauge the tightest point.
Draper Draper 98921 well pump

Testsieger

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

A slim pump in a wide hole

A 75 mm pump can hang in a dug well half a metre across, and fit is not the only question. The motor is usually cooled by water moving past the body. A wide dug well is the Draper’s job in this set when 40 metres of headline head is enough. None of these listings includes a cooling sleeve. If you need 80 metres or more in a wide shaft, that cooling question belongs with a supplier.

When each shape

Choose the wide pump when the opening clears 24 cm, the water is a dug well, a tank or a river, and your total head sits inside a 40 metre headline with flow left over. In this set that is the Draper 98921 at £124.13. Skip it for every drilled casing. Choose a 75 mm pump only when you have measured at least 85 mm inside, and only for the SDM 24 or the STM 28, which are the listings that say so. Both still clash between 20 metres and 1.5 metres of cable, and neither has reviews. The STM 24 does not inherit that 85 mm line. The 98 mm SKM needs room around the body plus the cable, and its cord is 15 metres. Which of those slim pumps to skip is the best deep well pump page.

Common questions

I have a dug well. Do I need a borehole pump?
Not from the name. A dug well that clears 24 cm is the Draper’s geometry, at 40 metres headline head and 5460 litres an hour at the other end of the curve. A 75 mm pump can hang in a wide shaft, and cooling then becomes the problem because flow past the motor may be too slow.
Will the Draper go down a 4 inch casing?
No. The listing size is 33 × 24 × 18 cm, so the body is 24 cm wide. A 4 inch casing is nominally about 102 mm. The Draper is a wide well pump for a dug well, a tank or a river. UK reviews describe those jobs. The price and the star line do not change the width.
The title says 3 inch and the body is 75 mm. Is that the same as the hole?
No. The body is 75 mm. A nominal 3 inch hole is about 76 mm, which is not a practical gap for the cable and the joint. AES puts a typical pump for a 3 inch hole at or under about 68 mm outside. The SDM 24 and the STM 28 ask for 85 mm inside. Measure the casing.
Why do two listings ask for 85 mm inside?
Because a 75 mm body plus the cable and the coupling needs more than a nominal 3 inch bore. The SDM 24 and the STM 28 both write a minimum internal diameter of 85 mm. The STM 24 is also 75 mm and does not write that minimum, so do not copy it across.
The 4 inch SKM is 98 mm. Is a 4 inch hole enough?
Often it is not, once the cable is included. AES’s typical outside diameter for a 4 inch hole is at or under about 96 mm, and this pump is already 98 mm. The bullet says minimum 4 inch wells. That is a claim, not a measured clearance. Gauge the tightest inside diameter.
Can I hang a 75 mm pump in a wide well?
You can get it into the well. Cooling is separate, and none of these listings includes a sleeve. Grundfos’s 0.15 metres per second figure is for groundwater above 30 °C, not a cold-UK rule and not a test of these pumps. If the well is wide and 40 metres of headline is enough, the Draper is the shape in this set.

Related pages

Garden pump or deep well pump

Deep well pump

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

Deep well pump buying guide: measure head and bore

How to install a deep well pump: pipe, valve, stop

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)