Pump advice & FAQ
Everything we end up explaining on the phone, written down. Work through the sizing guide before you buy anything — it takes about ten minutes and it is the difference between a pump that lasts a decade and one that dies in a season.
Sizing a pump
The four numbers you need, and a worked example.
ReadChoosing a type
Booster, submersible or surface — decided by your water source.
ReadMaintenance
Seasonal servicing and winterising for the Irish climate.
ReadTroubleshooting
Cycling, no water, low pressure, noise — diagnosed.
ReadFull FAQ
Choosing, installing, running, and ordering questions.
ReadHow to size an irrigation pump
A pump is specified by two numbers working together: flow (how much water per minute) and head (the total resistance it has to push against, measured in metres). Every pump has a curve showing what flow it delivers at what head. Your job is to work out your duty point, then buy a pump whose curve comfortably covers it. The calculator further down does the whole thing for you, including the parts people forget — lift out of the water, filtration losses and the suction side.
The single most useful conversion to remember: 1 bar of pressure = 10.2 metres of head.
Step 1 — Work out your flow demand (L/min)
Add up everything that runs at the same time. Do not add up everything you own — if you zone the system, you only size for the biggest zone.
- Drip emitters: typically 2–4 litres per hour each. 500 emitters at 2 L/h is 1,000 L/h, which is only about 17 L/min.
- Micro-sprinklers: roughly 40–120 L/h each.
- Impact/rotor sprinklers: roughly 8–15 L/min each — these are what drive the pump size.
- Hose reel or rain gun: check the manufacturer figure; these can be 100 L/min or far more.
Step 2 — Measure your static head (m)
The vertical distance from the water surface to the highest emitter. If your water sits in a stream 4 m below the pump and the top of the field is 6 m above it, your static head is 10 m. Horizontal distance does not count here — that is step 3.
Step 3 — Add friction loss (m)
Water rubbing against pipe wall costs you pressure. It rises sharply with flow and falls sharply with pipe diameter, which is why undersized pipe is the most common and most expensive mistake on an irrigation job.
Rule of thumb
Keep water velocity under about 1.5 m/s. Then estimate friction loss at roughly 4–14 m per 100 m at that velocity — narrow pipe loses far more than wide — and add 10% on top to cover bends, valves and filters. If in doubt, go one pipe size up — pipe is cheap, electricity is not.
Step 4 — Add the pressure your emitters need (m)
Emitters do not work on leftovers. They need a stated pressure at the nozzle:
- Drip line: about 1–1.5 bar (10–15 m)
- Micro-sprinklers: about 1.5–2 bar (15–20 m)
- Rotor sprinklers: about 2.5–3.5 bar (25–36 m)
Putting it together
Total head = static head + friction loss + emitter pressure. Here is a worked example:
| Demand | 12 rotor sprinklers × 10 L/min = 120 L/min |
|---|---|
| Static head | Water 2 m below pump, field rises 4 m = 6 m |
| Friction loss | 80 m of 63 mm MDPE + fittings = 1.9 m |
| Filter and valves | Design allowance across filtration and the zone valve = 2 m |
| Emitter pressure | 2.5 bar at the nozzle = 25.5 m |
| Total duty point | 120 L/min at 35.4 m (3.5 bar) |
| What to look for | A pump whose curve covers that point with about 15% in hand — so at least 138 L/min at 40.7 m |
That margin matters. Aim for a pump that hits your duty point somewhere in the middle of its curve, not at the very end of it. A pump running flat out at the edge of its range runs hot, runs loud and wears out fast.
Work out your duty point
Five short steps. It returns the two numbers every pump is specified by — flow and total head — plus the smallest pipe that will carry it without wasting your electricity. It accounts for lift out of the water, friction, filtration and the pressure your emitters actually need. Rough figures are fine.
Which type of pump do you need?
This is decided almost entirely by where your water sits and how far below the pump it is — not by budget or by how big the job feels.
Maintenance & winterising
Irish frost is not severe but it is frequent, and a pump casing full of water that freezes once will crack. This is the routine we recommend.
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MARCH — SPRING START-UP
Recommission before the season
Check the vessel pre-charge with a tyre gauge (should be about 0.2 bar below cut-in pressure), flush the filters, inspect the foot valve, and run the system through every zone before you actually need it.
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MAY — AUGUST · IN SEASON
Watch pressure, not the calendar
A slowly falling delivery pressure means a blocking filter or a wearing impeller. A rising pressure means a blockage downstream. Either way, a gauge on the manifold tells you weeks before a failure does.
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SEPTEMBER — ANNUAL SERVICE
Seals, bearings and electrics
Once a year: check the mechanical seal for weeping, listen for bearing noise, and confirm the pressure switch contacts are clean and not pitted.
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OCTOBER — WINTERISING
Drain everything that can freeze
Open the drain plug and empty the pump casing completely. Drain or blow out above-ground pipework and dripline. Isolate the supply. Submersible pumps below the frost line can usually stay put — the riser above it cannot.
Troubleshooting common faults
Four faults account for most pump problems. Work through these before you assume the pump has failed.
Called short-cycling. It is the fastest way to kill a motor, and it is nearly always one of three things:
- Lost air pre-charge in the pressure vessel. Most common by far. Isolate and drain the system, then check the air valve on the vessel with a tyre gauge. It should read about 0.2 bar below the pump cut-in pressure. If it reads zero, the internal bladder has usually failed.
- Leaking non-return or foot valve. Pressure bleeds back down after the pump stops, so it restarts. Isolate sections to find where the pressure is dropping.
- Pressure switch set too tight. Too small a gap between cut-in and cut-out means the pump never gets a decent run. Widen the differential.
The pump has lost its prime or is drawing air. Check, in this order:
- Is the casing actually full of water? Re-prime it fully.
- Is the foot valve holding, and is the strainer clear of weed and silt?
- Any air leak on the suction side — a loose union, perished washer, or a cracked fitting? A suction leak draws air without leaking a drop of water, so you cannot spot it visually.
- Has the water level dropped below the foot valve? Common in a dry August.
Stop the pump while you diagnose. Running dry destroys the mechanical seal within minutes and is not covered by warranty.
- Blocked filter. Always check this first — it is free and it is usually the answer.
- Worn impeller. If you pump silty or sandy water, the impeller erodes and the curve drops.
- Partly closed valve or a crushed pipe. Especially where pipe crosses a track or gateway.
- More emitters than you started with. Adding zones to an existing system without resizing is the classic way to lose pressure everywhere at once.
A rattling sound like gravel in the casing is usually cavitation — the pump is trying to draw more than the suction side can give it. Causes: suction pipe too narrow, too long, blocked strainer, or a suction lift beyond the pump’s capability. Cavitation pits the impeller, so do not leave it running.
A steady mechanical whine or grinding is more likely worn bearings. Vibration that shakes the pipework usually means loose mounting bolts or the pump is not sitting level — fit flexible connectors and an anti-vibration mat.
Frequently asked questions
Filter by topic, or read the lot.
There is no answer based on area alone — a hectare of drip line needs a fraction of what a hectare of rotor sprinklers needs. What matters is your simultaneous flow demand in litres per minute and your total head in metres. Work both out with our sizing calculator, which does the arithmetic for you.
Measure how far below the pump position your water sits. If it is less than about 8 m, a surface or booster pump can draw it up. Beyond that, atmospheric pressure will not push water up the suction pipe no matter what you spend, and you need a submersible sitting in the water pushing it up instead.
Yes, but not at the same time. They need very different pressures — roughly 1 bar for drip against 3 bar for rotors. Run them as separate zones on a valve manifold, with a pressure regulator on the drip zone. Trying to run both together gives you burst dripline and sprinklers that barely turn.
If demand is constant — a zone running for an hour — you can manage without. If demand switches on and off, such as taps or livestock drinkers, then yes. Without a vessel the pump restarts on every small draw-off, and that short-cycling is what kills motors. A vessel gives the pump a decent run each time it starts.
Two ways of describing the same thing. Head is measured in metres of water column, pressure in bar. 1 bar = 10.2 metres of head. Pump manufacturers publish curves in metres; irrigation equipment is usually specified in bar, so you will convert between them constantly.
Size it so water velocity stays under about 1.5 m/s. On the MDPE coil usually sold here that works out at roughly: 25 mm up to about 29 L/min, 32 mm to about 47 L/min, 40 mm to about 75 L/min, 50 mm to about 117 L/min, 63 mm to about 186 L/min. Thicker-walled PE100 pipe has a slightly bigger bore and carries a little more. Long runs should go one size up, and never make the suction pipe smaller than the pump inlet. The sizing calculator does this for you and accounts for the pipe class you pick.
No. We are supply-only — we ship the equipment and you arrange fitting with your own plumber or electrician. We are happy to give them the pipework and wiring details they will ask for, at no charge.
Isolate the electrical supply, open the drain plug and empty the casing completely, then drain or blow out above-ground pipework and dripline. Water left in a casing that freezes will crack it, and that is not a warranty repair. Full routine in our maintenance section.
Once a year for a domestic or garden system, checked before the season rather than after it. Commercial systems running most of the summer deserve a mid-season filter check too. The vessel pre-charge is the one item people forget and the one that causes most failures.
On any submersible, and on any surface pump drawing from a source that could run low, yes — strongly recommended. A dry-run device costs a small fraction of a pump and prevents the single most common uncovered failure. Some models include it; check the specification tab on the product page.
Technically straightforward with a surface pump, a foot valve and a good strainer. Legally, abstraction from watercourses in Ireland may require registration or authorisation depending on volume and location. Check with your local authority or the EPA before you commit to a design — we can spec the pump, but we cannot advise on your abstraction rights.
Delivery cost and timing are shown at checkout before you pay. Orders are fulfilled directly by our supplier rather than shipped from our own warehouse. Larger pump sets may ship on a pallet. If you need a firm delivery date before ordering, ask us and we will confirm it with the supplier.
Every pump carries a - year warranty against manufacturing defects, covering parts and labour. It does not cover damage from running dry, frost, incorrect wiring, or pumping abrasive or chemically aggressive water the pump was not specified for. Your statutory consumer rights are unaffected.
Yes — - days, provided it is unused and in its original packaging. Once a pump has been wetted we cannot resell it, so please check the sizing before you install. If you are unsure, run your figures through the sizing calculator first.
Product prices are shown ex VAT with the inclusive figure alongside. Irish VAT at 23% is applied at checkout. VAT-registered businesses elsewhere in the EU can supply a valid VAT number for zero-rating where the rules allow.
We do, for installers, landscapers, growers and groundskeeping contractors buying regularly. Get in touch with your business details and we will set up an account with agreed terms and pricing.
Question not answered here?
Call +353 87 348 3673, email info@irrigationsupply.ie, or send us a message. We answer pump questions whether or not you are buying from us.