Lay flat hose is the workhorse of temporary water transfer: it rolls up small, weighs little, and costs a fraction of rigid pipe. It is also routinely misused — undersized, over-pressured, or put on the wrong side of the pump.
What it is
A PVC tube with high-strength polyester reinforcing fibre woven into the wall. Empty, it collapses flat and rolls into a compact coil. Under pressure it takes a round section and behaves like pipe.
Rural Max lay flat hose is rated to 4 bar working pressure, is odourless, and is available from 1” to 4” in 25 m, 50 m and 100 m rolls.
Sizing: match the hose to the flow, not the pump outlet
The most common mistake is buying hose to match the pump’s outlet thread. The outlet size is a connection detail. The hose should be sized for the flow you are actually moving.
Push too much water through too small a hose and velocity rises, friction loss climbs steeply, and you lose pressure and flow at the far end. Keeping velocity around 2 m/s is a sound working target:
| Hose size | Comfortable flow | Roughly |
|---|---|---|
| 1” (25 mm) | up to ~60 L/min | Garden pump, single outlet |
| 1.5” (38 mm) | up to ~135 L/min | Larger domestic pump |
| 2” (50 mm) | up to ~235 L/min | Transfer pumps, irrigation |
| 3” (76 mm) | up to ~540 L/min | High-volume transfer |
| 4” (100 mm) | up to ~940 L/min | Flood irrigation, major dewatering |
Matching to the Rural Max range
| Pump | Max flow | Outlet | Recommended hose |
|---|---|---|---|
| RM-JP100 | 55 L/min | 1” | 1” |
| RM-SJP800 | 55 L/min | 1” | 1” |
| RM-JP200 | 130 L/min | 1” | 1.5” |
| RM-DJSM1025 | 90 L/min | 1” | 1.5” |
| RM-TF1 | 267 L/min | 1.5” | 2” |
| RM-CP-4 | 200 L/min | 2” | 2” |
| RM-CP-3 | 500 L/min | 2” | 3” |
| RM-QDX370 | 97 L/min | — | 1.5” |
| RM-QDX1100 | 467 L/min | — | 3” |
| RM-WQD7 | 350 L/min | — | 3” |
| RM-WQD15 | 333 L/min | — | 3” |
Note the RM-TF1 and RM-QDX1100 in particular. Matching hose to their outlet size would throttle them badly — the TF1’s 267 L/min through 1.5” hose runs at nearly 4 m/s, roughly double a sensible velocity, wasting a large share of the pump’s output as friction.
Going one size up costs little and pays back immediately in delivered flow.
The 4 bar rating, and why it matters
4 bar is roughly 40 metres of head. That is the working pressure the hose is built for, and it is not a suggestion.
Several pumps in the range can exceed it. The RM-JP100 produces up to 43 m (4.2 bar) and the RM-JP200 up to 50 m (4.9 bar) — both above the hose rating at shut-off.
In normal use, with water flowing, pressure sits well below maximum head and the hose is fine. The risk is dead-heading: running the pump against a closed outlet. Flow stops, pressure jumps to the pump’s shut-off head, and the hose sees its maximum.
Practical precautions:
- Never run a pump against a closed valve at the end of a hose run.
- Open the outlet before starting the pump.
- On systems where the pump can exceed 4 bar, fit a pressure relief valve or use rigid pipe.
- Watch for ballooning, which means the hose is over-pressured — shut down immediately.
Choosing a length
Available in 25 m, 50 m and 100 m rolls.
- 25 m — around the yard, filling troughs nearby, short transfers.
- 50 m — the general-purpose length; long enough for most jobs, still manageable to roll.
- 100 m — dam to tank, paddock irrigation, long dewatering runs.
Buy the length you need, not more. Every extra metre adds friction loss. Two 50 m rolls joined when needed is more flexible than one 100 m roll always dragging its full length.
Estimate friction at roughly 5% of the run length in metres of head for correctly sized hose — so 100 m costs about 5 m of head. Undersized hose costs several times that.
Never use it on the suction side
Lay flat hose is a discharge-only product.
The suction side of a pump is under vacuum. Lay flat hose has no structural ring reinforcement — its shape comes from internal pressure. Apply a vacuum and it collapses flat instantly, blocking the pump. The pump then runs dry and damages its seal.
Suction lines need rigid pipe or purpose-built reinforced suction hose with a helical support coil. There is no exception to this, and it applies equally to the short section between a foot valve and the pump.
Connecting it
- Use camlock fittings for quick connection and disconnection — the standard for lay flat.
- Double-clamp barbed fittings where camlocks are not used. One clamp is not enough at 4 bar.
- Support the hose at the connection so its weight is not carried by the fitting.
- Avoid sharp bends near connections. Lay flat kinks readily, and a kink stops flow completely.
- On long runs, walk the line before starting to check for kinks and twists.
Looking after it
Drain it before rolling. Water left inside grows algae, freezes in winter, and makes the roll enormously heavy.
Roll rather than fold. Folding creases the PVC in the same place repeatedly, and cracks start at creases.
Do not drag it over abrasive ground. Concrete, gravel and steel edges wear the outer wall. Carry or roll it into position.
Keep it out of the sun when stored. UV degrades PVC over time. Store rolled, in shade, off the ground.
Watch for vehicle traffic. Driving over a pressurised lay flat hose can burst it. Where a hose must cross a track, use a ramp or bury the crossing point.
Inspect before each use. Look for cuts, abrasion, ballooning and hardened patches. A hose that has gone stiff and shiny has had too much UV and should be retired.
Quick reference
| Question | Answer |
|---|---|
| Can I use it on the suction side? | No — it collapses under vacuum |
| What pressure is it rated to? | 4 bar (~40 m head) |
| What size for my pump? | Size for flow, not outlet thread — see the table above |
| Can I join two lengths? | Yes, with camlocks |
| Can I drive over it? | No — use a ramp or a buried crossing |
| How should I store it? | Drained, rolled, in shade, off the ground |
For pipe sizing on the suction side and the fixed parts of a system, see Understanding Flow Rate, Head and Pump Curves.
