How to choose the right HDPE pipe size
How to choose the right HDPE pipe size in Kenya — match diameter, PN rating, flow and distance to your job. A practical sizing guide from Wasser Pipes, with a full size chart.
Wasser Pipes8 min read
Quick answer
To choose the right HDPE pipe size, match two things to your job: the diameter, for the flow you need, and the PN pressure rating, for the working pressure. As a rule of thumb in Kenya: 20–25mm for household connections and drip laterals, 32–50mm for sub-mains and small farms, 63–90mm for boreholes and estate mains, and 110mm for large distribution. Use PN6–PN10 for gravity and low-pressure lines, PN16–PN20 for pumped mains and boreholes. Wasser HDPE covers every size from 20mm to 110mm, made to DIN, TSE and ISO standards.
Why choosing the right HDPE pipe size matters
The size of your HDPE pipe decides how well your whole water system works. Too small, and you starve the far end of the line — weak flow at the tap, sprinklers that won't pop up, a borehole pump straining against back-pressure and burning energy. Too large, and you pay for material and fittings you didn't need.
Getting the diameter and pressure class right the first time gives you strong, even flow, low pumping costs and a system that lasts for decades. In Kenya, where water often travels long distances from a borehole, river or tank, correct sizing is one of the most important decisions you'll make.
The 4 factors that decide HDPE pipe size
HDPE pipe size chart (Kenya)
Wasser HDPE pipes run from 20mm to 110mm. Use this chart as a quick starting point, then confirm the exact size against your flow and distance:
| Diameter (mm) | Approx. inch | Best suited for |
|---|---|---|
| 20mm | ½" | Household connections, drip laterals, single taps |
| 25mm | ¾" | Home supply, small garden & kitchen plots |
| 32mm | 1" | Home & farm sub-mains, small drip blocks |
| 40mm | 1¼" | Sub-mains, small sprinkler lines |
| 50mm | 1½" | Mainlines for smallholder farms & small schemes |
| 63mm | 2" | Borehole rising mains, supply mains, greenhouses |
| 75mm | 2½" | Supply mains, medium farms & estates |
| 90mm | 3" | Larger distribution mains, multi-block projects |
| 110mm | 4" | Main distribution, municipal & large-scale lines |
Choosing the pressure class (PN)
Diameter is only half the decision — the PN rating sets how much pressure the pipe can safely hold. Choose it from how your water moves:
| PN class | Max pressure | Use it for |
|---|---|---|
| PN6 – PN8 | 6–8 bar | Gravity-fed lines, low-pressure drip irrigation |
| PN10 | 10 bar | General water supply & irrigation mains |
| PN16 | 16 bar | Pumped mains, boreholes, high-pressure supply |
| PN20 | 20 bar | Deep boreholes, industrial & municipal systems |
Rule of thumb: when a pump is involved or the ground rises, size the pressure class up rather than down.
Sizing HDPE pipe by application
How to choose the right HDPE pipe size, step by step
Know your flow rate. Work out how much water you need per hour — from your pump output, tank size, or the number of outlets running at once.
Match the diameter to the flow. Pick a bore big enough to carry that flow comfortably; a slightly larger pipe loses less pressure to friction.
Choose the pressure class (PN). PN6–PN10 for gravity and drip, PN16–PN20 for pumped mains and boreholes.
Account for distance and elevation. For long or uphill runs, step the diameter up so pressure holds to the far end.
Confirm and buy matching fittings. Verify the size against your application and order pipe and fittings together from a trusted manufacturer like Wasser Pipes.
Common HDPE pipe sizing mistakes to avoid
Why buy your HDPE pipe from Wasser Pipes
Choosing the right size only pays off if the pipe genuinely performs to its rating — and that comes down to the manufacturer. Wasser Pipes, made by Astral Industries Limited, is built to deliver exactly what the label promises:
- Every size, one manufacturer. The full range from 20mm to 110mm in PN6 to PN20 — so you get the precise diameter and pressure class your job needs, not the nearest guess.
- Made to international standards. Manufactured to DIN, TSE and ISO, so a PN10 pipe really holds 10 bar and the wall thickness you pay for is what you get.
- Genuine, correctly-rated material. Properly formulated PE resin means true pressure performance and a 50-year service life — no thin walls, no under-rated pipe.
- Expert sizing support. As a Kenyan manufacturer, Wasser helps you calculate the right size and pressure class, and supplies the matching fittings.
- Long coils, nationwide delivery. Supplied in 50m–100m lengths to cut joints and speed installation, delivered across Kenya.
Get the size right and the pipe right. Choose Wasser HDPE — request a quote today.
Keep reading
HDPE Pipes in Kenya (2026): Sizes, Prices, Uses & Buying GuideSizes, PN pressure ratings, prices and applications — everything that decides which HDPE pipe your borehole, farm or water scheme needs.Read the guide
What Is an HDPE Pipe & How Does It Work?The structure, the smooth bore, the fused joints — a plain-English explanation of what makes an HDPE pipe last fifty years.Read the guide
Get the right HDPE pipe size from Wasser Pipes
Send us your water source, distance, flow and application — we'll calculate the exact diameter and PN class, and quote genuine Wasser HDPE pipe and fittings together.