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Suction, discharge, clean water, hydrocarbons, food liquids: not every hose is the same. The right hose depends on the liquid handled, the type of stress (vacuum or pressure), the diameter and the working pressure. Here is how to avoid mistakes.
Suction or discharge: the first question
On the suction side, the pump creates a vacuum: an ordinary flexible hose flattens, the flow drops and the pump may lose its prime. You need a suction hose with a reinforced wall (usually a rigid spiral) that stays round under vacuum. On the discharge side, internal pressure is what counts: the hose must withstand the pump pressure with a margin. Some models in the suction and delivery hoses category do both; the product page gives the permitted pressure and vacuum.
A surface pump does not really “pull” water: atmospheric pressure pushes it up. Suction lift is therefore limited (in practice more like 6 to 8 m) and the slightest air leak in the hose or couplings can stop everything. Fit the submerged end with a foot valve with strainer to keep the water column and filter debris.
The main hose families
| Use | Hose type | What to watch |
|---|---|---|
| Water suction | Flexible PVC hose or spiral-reinforced rubber hose | Vacuum resistance; perfectly sealed couplings |
| Worksite discharge, drainage | Lay-flat discharge hose (rolls flat once emptied) | Discharge only, never for suction; working pressure depends on the model |
| Pressurised discharge, fixed installation | Rubber or reinforced PVC hose | Working pressure above the pump pressure |
| Fire fighting | Fire hose | Site regulations; couplings of the right system |
| Hydrocarbons, fuels | Hydrocarbon-resistant hose | Suitable inner lining; site safety rules |
| Food liquids | Food-grade hose | Food use stated on the product page; cleaning |
| Compressed air, washing, watering | Hoses dedicated to each use | Not a substitute for a liquid transfer hose |
The right diameter: do not choke the pump
Basic rule: the suction hose diameter must never be smaller than the pump suction port, and it is better to go larger if the run is long. The longer, narrower or more bent a hose is, the more friction losses it creates, and these add to the lift to overcome in the total dynamic head calculation.
Worked example: same flow, two diameters
A pump delivers 12 m³/h, or about 200 l/min. In a hose with a 50 mm inside diameter, water flows at about 1.7 m/s; in a 40 mm hose, at about 2.7 m/s (velocity = flow ÷ cross-section). Friction losses rise faster than velocity, roughly with its square: the smaller diameter causes clearly more, especially over a long run or on the suction side, where a moderate velocity is generally sought.
Working pressure, liquid and temperature
- Working pressure: this is the pressure the hose withstands in normal use, not to be confused with burst pressure. Choose a working pressure above the pump’s maximum pressure, allowing for surges (starts, sudden valve closures).
- Liquid: clean water, dirty water (the inner wall wears), hydrocarbons, food or chemical liquids do not call for the same hose. Never assume compatibility: check it on the product page.
- Temperature: minimum and maximum operating temperatures are given on the product page; hot water needs a model designed for it.
- End fittings: hose tails and clamps, or quick couplings: see the guide /en/content/20-guillemin-storz-dsp-couplings-identify-match.
For fuel, fire fighting or explosive atmospheres, apply general safety rules, follow the manufacturer’s instructions and the regulations applicable to your site (insurer, fire service, environmental authority…).
Method: choosing your hose in 5 steps
- Define the role: suction, discharge, or both.
- Identify the liquid (type, temperature, presence of sand or particles) and choose the matching hose family.
- Note the pump’s maximum pressure and take a higher working pressure; for suction, check the vacuum resistance.
- Choose the diameter: at least that of the pump port, larger if the run is long; check the flow velocity.
- Choose the length and end fittings: as short as possible on suction, with suitable clamps or couplings.
Frequently asked questions
Can I draw water with a garden hose?
Generally not: its soft wall flattens under vacuum. Use a reinforced suction hose, whose product page states its vacuum resistance.
What is the difference between working pressure and burst pressure?
Working pressure is what the hose withstands in normal use; burst pressure is the failure limit, which you never aim for. Base your choice on the working pressure.
Can a lay-flat hose be used for suction?
No: it is designed for discharge and collapses under vacuum. Keep it for drainage and pressurised transfer, as indicated on the product page.