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Fittings are the most project-specific part of any flexible water tank order. Unlike rigid tanks with fixed outlet positions, flexible tanks are manufactured with fittings positioned, sized, and configured to your project specification. Getting the fitting specification right before production begins avoids delays, additional cost, and — in the worst case — a tank that cannot connect to your site infrastructure.
Why Fittings Matter More Than Most Buyers Expect
A flexible water tank without correct fittings is unusable on site. The tank fabric is a commodity — the fittings are what connect your tank to your pump, hose, gravity feed, or pressure line. Specifying fittings incorrectly, or leaving them ambiguous in a purchase order, is the most common reason B2B buyers experience problems with their first flexible tank shipment from China.
Inlet Fittings
The inlet is how water enters the tank. Standard options include:
- Camlock (cam and groove) coupling — the most common fitting for bulk water transfer. Available in DN50 (2 inch), DN75 (3 inch), and DN100 (4 inch). Fast to connect and disconnect, widely compatible with pump hose fittings used in construction and agriculture.
- BSP threaded (male or female) — the standard thread for plumbing connections in most markets outside North America. Specify BSP clearly in your order.
- NPT threaded — used in North American markets. Ensure your supplier knows which thread standard applies to your destination.
- Flanged connection — used for permanent or semi-permanent installation where the fitting bolts to a fixed pipe. Less common for collapsible tanks but available on request.
Outlet Fittings
The outlet is how water exits. In most pillow and cube tank configurations, the outlet sits low on the tank wall or at the base to allow gravity drainage. Standard options mirror the inlet choices above — camlock, BSP, and NPT — with the addition of a ball valve pre-fitted to the outlet for flow control without an external valve, and a blank-off cap for buyers who prefer to connect their own valve on site.
Drain Fittings
A dedicated drain fitting sits at the lowest point of the tank floor, allowing complete emptying without tilting or pumping. This is important for large tanks above 5,000L that cannot be physically tilted, food-grade or potable water applications requiring full draining and cleaning between uses, and any installation where residual water pooling is a concern.
Standard drain fittings are DN50 (2 inch) BSP or camlock, positioned at the lowest floor point of the tank.
Overflow and Vent Fittings
Tanks filled by pump without automatic shutoff require an overflow fitting to prevent overpressure damage to the seams. A vent fitting — typically small-diameter DN25 — at the top of the tank allows air displacement during filling without creating air locks. These are frequently overlooked in initial specifications and then requested as modifications after manufacturing. Include them in your original order specification.
Number and Position of Fittings
A standard flexible water tank order specifies one inlet (top or side, DN50 to DN100), one outlet (low side, same diameter as inlet or one size smaller), one drain (floor-mounted, DN50), and optionally one vent (top, DN25). Custom configurations — multiple inlets, elevated outlets for gravity feed systems, side-mounted drains for sloped sites — are available but must be specified before production. Fitting positions cannot be changed after manufacturing.
Fittings Pre-Attached vs. Packed Separately
For smaller tanks, fittings are typically factory-welded into the fabric before shipment. For larger tanks or mixed orders, some buyers prefer fittings shipped separately and attached on site — this reduces the folded size of each tank and can simplify customs classification in some markets. Specify your preference at order stage.
Getting the Specification Right
Before confirming your order, provide your manufacturer with: fitting diameter (DN size), thread standard (BSP or NPT), connection type (camlock, threaded, or flanged), position on the tank (top, side, or base), quantity of each fitting type, and whether you need valves pre-fitted or capped outlets.
ZolinWorks confirms all fitting specifications in writing as part of the order specification sheet before production begins. Send your project requirements and we will prepare a configuration outline for your review before the order is confirmed.
Further reading: If you are still narrowing the right tank format, compare the ZolinFlex pillow range and our construction sizing guide. For project-specific fitting layouts, send an enquiry.