PVC Hose Working Pressure — The Numbers That Keep Hose Honest

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The hose pages on this site state their pressure figures openly — layflat at 2 to 10 bar working, suction at 3 to 8 bar, garden at 5 to 8 bar among them — each a family range across that family's bores, with the rating at any one bore confirmed in the quotation — and every figure deserves the same buyer question: at what bore, under what definition, with what margin behind it? Pressure literacy is the difference between a hose specified as equipment and a hose bought as a commodity. This guide covers the four ideas that do the work: working pressure, burst pressure, family ranges versus per-size ratings, and margin — with the conversions buyers in psi markets need.

Working pressure and burst pressure

Working pressure (WP) is the maximum continuous service pressure the hose is rated to carry in normal duty — the number your system pressure, including its ordinary surges, must stay under. Burst pressure (BP) is the pressure at which a new hose of that construction fails in a test — a destructive figure you should never approach in service, whose real job is to demonstrate margin. In this manufacturer's published data, both figures are stated as family ranges: layflat at 2 to 10 bar working and 6 to 30 bar burst, suction at 3 to 8 bar working and 9 to 24 bar burst, garden at 5 to 8 bar working and 15 to 26 bar burst. Read those as ranges, not as pairs: the endpoints of two family bands are not a working and burst figure measured on the same hose at the same bore, so no single safety factor for a construction can be read off them. The margin behind the size you are buying is established by that size's own working and burst figures and the test basis behind them — which is why both are confirmed at your bore in the quotation. An offer that cannot state a burst figure at all, or that will not put the working-pressure figure for your bore in writing, has left you nothing to check its margin against.

A family range is not a rating for your size

The figures quoted for these families are published as ranges: one band of working pressures and one band of burst pressures for a whole construction family, across every size it is made in. A range like that cannot tell you the rating of the size you are buying — its endpoints are the family's published limits, not a rating measured for your bore. A single pressure printed for a family is not a size rating; the figure that governs an order is the pressure confirmed at your bore in the quotation. When you compare offers, ask every supplier for the same three things: the rated working pressure at your exact inside diameter, for the construction offered, at your service temperature — and the test basis behind the figure. An offer that answers only with the family headline has not answered the question. Where a family does publish per-size figures, the difference is plain: the steel-wire burst figures reproduced on the steel wire page run from 30 bar at the small diameters to 6 bar at 8 and 10 in — one family, very different numbers by size, which is exactly why the per-size figure is the one to order against.

Conversions and system pressure

Conversions between the endpoints are linear — multiply bar by roughly 14.5 to get psi — but a converted figure is still a family-range figure, not a rating for your size; the rating at your bore is the figure the quotation confirms.

System pressure means the worst the hose will actually see, not the pump's badge. Add the pump's shut-off head — the pressure at zero flow, which is what a closed valve or a blocked line delivers to the hose — and any water hammer your system generates when valves snap shut. Long lines, fast-closing valves and high static lifts all argue for margin. The practical rule for buyers: state in your enquiry the maximum pressure the hose can ever see, including shut-off, and let the factory select the class.

Temperature: the published envelope

Published ratings in this range sit inside a published temperature envelope — minus 5 to plus 65 degrees Celsius on the layflat, suction and garden pages. PVC softens as temperature rises, so a hose at its pressure limit on a cold morning is a different proposition from the same hose at its limit in hot sun with hot water; where duty approaches both limits at once, raise it in the enquiry and have the class for that duty confirmed in the quotation.

Auditing a supplier's pressure claim in five questions

• At which bore? A figure without a diameter is a family maximum in disguise; pin it to your size.
• What is the burst pressure at that bore? A working-pressure figure cannot be checked on its own; ask for the burst figure at the same bore, for the same construction, and the test basis behind both figures.
• Within what temperature range? Ratings live inside a published temperature envelope, and an honest sheet says where its numbers live.
• Tested how, and evidenced where? A rating that traces to a test report for that construction outranks a rating that traces to a brochure.
• What does the quotation repeat? The figure that matters is the one the supplier will print against your order; ask for it there, in writing, at your bore.

Run those five questions against any offer — including every page of this site, whose family pages state ranges, attach them to constructions and reserve the at-bore figure for the quotation — and the answers are what separate an engineering claim from an advertising one. Keep the answers with the order documents. If a hose ever fails in service, the record worth having is the pair of numbers agreed in advance: what pressure the hose was rated for at that size, and what pressure it saw.

Pressure in the real system: pumps, valves and gravity

A pump rated at a 6 bar duty point feeds a layflat line uphill to a tank. At full flow the hose sees something near the duty pressure, less friction. Close the tank valve quickly and two things happen: the pump runs toward its shut-off head — higher than the duty point — and the moving column of water, stopped suddenly, adds a surge on top. The hose at the pump end briefly sees the sum, on a hot afternoon, in its third season. None of it is exotic. The discipline is to choose the working pressure at your bore against the system's worst honest moment rather than its nameplate average. That is the whole discipline of pressure specification — deciding, in advance and in writing, which moment you are engineering for.

Is burst pressure ever a usable number?

Only as evidence of margin. Design and specify against working pressure with your system's worst case inside it; burst is the figure that proves the gap exists.

My pump says 6 bar — do I need a 6 bar hose?

You need a hose whose working pressure at your bore covers the maximum the hose can see, which includes shut-off head and surge, not just the pump's nominal duty point. State the pump curve facts in the enquiry, and check the class quoted against them before ordering.