Threaded brass swing check valve, 1/2" to 4"

A swing check valve in 1/2" to 4" (DN15 to DN100), with NPT threaded ends and a body in Brass throughout. The gasket is PTFE. Rated 200 PSI on 1/2" and 2½", 300 PSI on the other seven as published for service at not published.

It is a disc on a hinge. Forward flow pushes it open and holds it clear of the bore; when flow stops or reverses, the disc swings shut under its own weight and the backpressure behind it. Nothing operates it — no handle, no stem, no actuator — which makes it the cheapest way to stop a stopped pump being spun backwards, and the least visible when it stops working. How it works, in full.

• The rating is carried in the part number. Seven of the nine sizes read ‑300‑ and two read ‑200‑ — the 1/2", which has “200 WOG” cast into the body (visible in the first photograph above), and the 2½". State the size on your enquiry and the rating is confirmed on the quotation.
• The rating is the PSI figure in the part number and in the casting. The catalogue does not print a test table or a working temperature for this variant; we obtain shell and seal figures from the factory on request.
• The range is 1/2" to 4", DN15 to DN100, with full dimensions and part numbers for every size.
• Brass all the way through, including the pin. Body, disc, cap, pin, plain washer and bolt are all brass, with PTFE gaskets. That means no galvanic pair inside the valve — and also no corrosion resistance beyond what brass gives you. On anything aggressive, use the SS316 version.
• ⚠ Brass and hot water do not mix indefinitely. Dezincification thins brass over time in some water chemistries, and there is no published temperature limit for this valve to design against. On heating circuits or anything above ambient, we would use stainless.
• Weights are published for every size, from 0.13 kg at 1/2" to 4.20 kg at 4" — a fraction of the flanged equivalents. A 4" brass check valve weighs less than a 1½" flanged one.
• NPT only. No BSPT option on this variant. If your pipework is BSPT, the threaded SS316 valve offers both thread forms.
• ⚠ Fit a Y‑strainer upstream. A flake of scale between disc and seat holds the disc fractionally open, and the valve then passes reverse flow while looking perfectly normal from outside. There is no stem position or indicator to check. A strainer is the single most effective thing you can do for a check valve.
• Orientation is not optional. Flow follows the arrow cast into the body; on a horizontal run the bonnet points up; on a vertical run flow must be upward. Never on downward flow — use a spring check for that. The three rules.

Four angles on the same valve. Photographs of the stocked item, not renders.

The manufacturer’s sectional drawing. The callout numbers correspond to the item numbers in the parts list.

• The disc and the seat face are what wear. Everything else is a casting or a fastener. On a valve that closes every time the pump stops, those two surfaces take the whole duty cycle.
• The hinge pin is the other one to ask about. A disc that chatters — which happens when the valve is oversized for the flow — wears the pin, and a worn pin lets the disc sit crooked on the seat.
• The item numbers are the manufacturer’s, matching the callouts on the drawing above, so a spares order matches the section.
• Everything here is published, not on request. If you need to know what touches your fluid, the whole list is above.

The other four variants each publish a test table — a shell test, a seal test, an air test and, on two of them, a temperature range. This variant publishes none of it. There is no test table on the manufacturer’s sheet, not a blank one, and no working temperature anywhere on the page. The only rating it carries is the PSI figure in the part number, and the one cast into the body.