Home › Products › Low pressure valves › Dual plate check valves

1½" to 6" · up to 300 PSI · seven flange standards

Dual plate check valves, 1½" to 6"

Q: What is a dual plate check valve?

A ring with two half-discs in it , hinged on a shaft straight across the middle and held closed by a torsion spring . Forward flow folds the halves back like swing doors; when flow falls away the spring folds them shut. The body is a wafer - a thin ring with no bolt holes, clamped between two pipe flanges - so it takes almost no length in the run. 1-1/2" to 6" , up to 300 PSI , in seven flange standards.

Q: Why choose it over a swing check?

Two reasons. Length: a wafer body sits between the flanges, where a flanged swing check at 6" needs 356 mm of pipe run to itself. Slam: two light half-discs, spring-assisted and travelling a short distance, close far more gently than one heavy disc swinging through 90deg and waiting for the flow to reverse first. On long lines and high-head pumps that is the whole argument. The cost is more pressure drop - the shaft, the spring and the disc edges all sit in the flow.

Q: Which flange standard do I need?

Whichever your pipework is - and you must state it when you order . This range is offered in seven : ANSI 150 and 300, JIS 5K and 10K, PN10, PN16 and PN40. A 4" dual plate check valve is not one product but seven, and they are not interchangeable . The full list .

Q: Is it really 300 PSI?

"Up to 300 PSI" is a range across seven flange standards, not a single rating . It plainly refers to the ANSI 300 and PN40 versions - a PN10 body cannot be 300 PSI. The manufacturer does not publish a breakdown by standard, so ask us for the rating of the one you are actually ordering and we will get it before you commit.

Q: Is it 316 or 304?

The specification says CF8M , which is cast 316. The discs on the stocked valve are cast CF8 , which is cast 304 - the marking is legible on both halves in the first photograph . On clean fresh water the difference is academic. On anything chloride-bearing it is not, because 304 pits and the first thing pitting affects on a check valve is the seat face. Tell us if your duty is chloride-bearing and we will confirm the grade for your exact size and flange standard. The full explanation .

Q: Can I fit it upside down?

Yes. A spring closes it, not gravity, so it works in any orientation including a vertical run with flow downward - which a swing check valve cannot do at all. The one rule that still applies is direction : flow must follow the arrow, and fitted backwards any check valve blocks the line.

Q: Can it sit at the end of a line?

No. A wafer body has no bolt holes of its own - it is held in place by the flange bolts passing either side of it . Take one flange off and the valve is no longer held. If it must terminate a run you need a lugged body, which is a different product; ask us.

Q: How long is it? I need to check clearance.

No dimension table is published for this range - no face-to-face, no body outside diameter. Tell us the size and flange standard and we will measure a stocked valve , same day. The body outside diameter matters as much as the length on a wafer valve, because it has to sit inside the flange bolt circle without fouling the bolts.

Q: What sizes do you hold in stock?

1-1/2" to 6" (DN40 to DN150), held in Malaysia or Singapore . Send the size, the flange standard , the fluid and - if slam is what you are solving - the line length and pump head . We will confirm availability, get the rating for your standard, and quote a landed price.

Two spring‑loaded half discs that fold together in the middle — in a wafer body that fits between two flanges. The answer when a swing check would slam, or when there is no room for one.

Request a quote Seven flange standards

1½" to 6"DN40 to DN150

Up to 300 PSIThe highest wafer check here

7 flange standardsANSI, JIS and PN

Wafer bodyFits between the flanges

How a dual plate check valve works

Two half discs, one shaft, one spring.

A dual plate check valve is a ring with two half‑discs in it, hinged on a shaft straight across the middle and held closed by a torsion spring wound round that shaft. Forward flow folds the two halves back against the spring like a pair of swing doors; when flow falls away the spring folds them shut again. The whole thing lives in a wafer body — a thin ring with no bolt holes, clamped between two pipe flanges.

Two consequences, and both are the reason this valve exists. It is very short, so it goes where a flanged check valve will not fit. And because each disc is half the diameter and travels a short distance with a spring already pushing it, it closes far more gently than a single heavy disc swinging through 90°. That is the standard answer to water hammer.

Short is the headline. A wafer body sits between the flanges. A flanged swing check valve at 6" needs 356 mm of pipe run to itself; a wafer check needs almost none.
Less slam is the other one. Two light half‑discs, spring‑assisted, moving a short distance, already closing as forward flow decays — against one heavy disc waiting for the flow to reverse before it starts. On long lines and high‑head pumps that difference is the whole decision.
It works in any orientation, including vertical with flow downward, because a spring closes it rather than gravity. A swing check cannot do that.
⚠ It costs more pressure than a swing check. The shaft, the spring and the two disc edges all sit in the flow, and the spring resists opening. A swing disc lifts clear of the bore entirely. You trade pressure drop for length and gentleness.
The disc grade: the specification states “Stainless Steel / CF8M”; the discs on the stocked valve are cast CF8 (304). You can read it in the photograph below. On chloride‑bearing duty, tell us and we confirm the disc grade for your order. What that means.
⚠ It still fails silently. Debris caught between a disc and its seat holds one half fractionally open, and the valve passes reverse flow while looking normal. Fit a Y‑strainer upstream.

Photographs of the stocked item, not renders.

Dual plate check valve viewed end on showing two half discs cast CF8, the central hinge shaft and the torsion spring between them — **1. End on, and the whole mechanismTwo half discs, a shaft across the middle, and the spring between them.** Both discs are cast **CF8** — you can read it on the metal — and the **torsion spring** wound round the shaft is what makes this valve close gently and work in any orientation.

Dual plate wafer check valve showing the thin ring body with machined faces and no bolt holes — **2. The wafer bodyA ring with no bolt holes.** It is clamped between two pipe flanges by their own bolts, which is what makes it so short — and also why it **cannot sit at the end of a line**.

Dual plate check valve seen at an angle showing the body rim and the discs partly open — **3. Body and discsEverything is inside the ring.** No bonnet, no cap, nothing protruding — which is why a wafer check weighs a fraction of the flanged equivalent and takes almost no room.

Seven flange standards

The widest choice of any valve on this site — and the reason to check before you order.

Because the body is a plain ring that sits between two flanges, one casting can be machined to suit several bolt patterns. This range is offered for seven different flange standards, which is more than anything else we stock:

Standard	Family	Nominal pressure	Also on the single plate?
ANSI 150#	American	Class 150	Yes
ANSI 300#	American	Class 300	No — dual plate only
JIS 5K	Japanese	5 kg/cm²	Yes
JIS 10K	Japanese	10 kg/cm²	Yes
PN10	European	10 bar	Yes
PN16	European	16 bar	Yes
PN40	European	40 bar	No — dual plate only

⚠ State the flange standard when you order, not just the size. A 4" dual plate check valve is not one product — it is seven, and they are not interchangeable. This is the most common ordering mistake on wafer valves.
The two extra standards are the high‑pressure ones. ANSI 300 and PN40 are offered on the dual plate and not on the single plate — which is exactly why the dual plate reaches 300 PSI where the single plate stops at 232.
A wafer body is centred by the flange bolts. It has no bolt holes of its own, so it must be held in place while the joint is pulled up. Most sizes have a lug or an eye for that; on the larger ones it is a two‑person job.
⚠ It cannot sit at the end of a line. Remove one flange and a wafer body is no longer held. If the valve must terminate a run, you need a lugged body — ask us, because it is a different product.
Do not mix standards across the joint. ANSI 150 and JIS 10K sit at similar pressures and are drilled differently. The valve is machined for one of them; the flanges either side must match it and each other.

CF8 and CF8M

The specification says one thing and the casting says another.

The published specification for this range gives the material as “Stainless Steel / CF8M”. CF8M is cast 316. But the discs on the stocked valve are cast CF8 — which is cast 304 — and the marking is legible in the first photograph on this page, on both halves.

Why it matters

316 contains molybdenum; 304 does not. That is what gives 316 its resistance to chlorides — seawater, brackish water, brine, chlorinated cooling water, and many process fluids.
On clean fresh water and general service the difference is academic and 304 is perfectly adequate.
On anything chloride‑bearing it is not academic at all: 304 pits, and on a check valve the first thing pitting affects is the seat face — which is where the valve seals.
The single plate valve in the same family is genuinely CF8M: its disc is cast “PN16 · DN40 · CF8M”, which we can also show you.

What we do about it

We publish both — what the datasheet says and what the metal says — rather than pick one.
If your duty is chloride‑bearing, tell us. We will confirm the disc grade with the factory for the specific size and flange standard you need before you order, because it may not be the same across the range.
If your duty is clean water, this is not worth a phone call and the valve is right for the job.
The body may well be CF8M even where the discs are CF8. Bodies and discs are separate castings and mixing grades is normal; that is one of the things we are asking.

Everything else in the valve is stainless too. The hinge shaft and the torsion spring are both stainless on the stocked item. The spring is the part doing the work every cycle, so it is the one worth having in a good grade.
⚠ No detailed bill of materials is published for this range. Unlike the swing check valves, which publish eight or nine numbered parts each, this one gives a single material line. What else is missing.

What is published, and what is not

A short datasheet. Here is exactly how short.

Published

Size range — 1½" to 6" (DN40 to DN150).
Working pressure — up to 300 PSI.
Material — “Stainless Steel / CF8M”, though the discs are cast CF8.
Seven flange standards — ANSI 150 and 300, JIS 5K and 10K, PN10, PN16 and PN40.
A manufacturer catalogue PDF, and photographs of the stocked item.

⚠ Not published

No dimension table. No face‑to‑face, no body outside diameter, nothing to check against your flange bore or the gap in the run.
No numbered bill of materials. One material line, against eight or nine numbered parts on every swing check variant.
No weights.
No test pressures — no shell test, no seal test.
No working temperature.
No cracking pressure, which on a spring‑loaded valve is what decides whether it suits a low‑head line.
No breakdown of which pressure goes with which flange standard. “Up to 300 PSI” plainly refers to the ANSI 300 and PN40 versions; a PN10 body will not be 300 PSI. Ask for the rating of the standard you are ordering.

⚠ “Up to 300 PSI” is a range, not a rating. Seven flange standards spanning PN10 to PN40 cannot all share one figure. The number that matters is the one for your standard, and it is not on the datasheet. We will get it before you order.
Ask us for anything on the right‑hand list. Dimensions we measure off a stocked valve, same day. Test pressures, temperature and cracking pressure we get from the factory.
The single plate valve publishes the same amount — which is to say, the same little. The two pages are honest about it in the same way.

Dual plate or single plate

The manufacturer publishes this comparison. We have added what it leaves out.

	Dual plate	Single plate
Disc	Two half discs folding together	One disc on a hinge
Body thickness	Thicker	Thinner
Weight	Heavier	Lighter
Cost	Higher	Lower
Working pressure	Up to 300 PSI	Up to 232 PSI (16 bar)
Flange standards	Seven — including ANSI 300 and PN40	Five — up to PN16 only
Disc travel	Shorter — each half moves half as far	Longer — one disc through a wider arc
Closing behaviour	Gentlest of the two	Gentle, but one larger disc arriving
Obstruction in the bore	More — a shaft across the middle plus two disc edges	Less — a hinge at one side
Choose it when	Pressure above 232 PSI, or slam is the main concern, or you need ANSI 300 / PN40	Weight and cost matter and PN16 is enough

The first five rows are the manufacturer’s own comparison. They are published on the single plate page as a straight dual‑versus‑single table, and they are reproduced here as printed.
The pressure and flange rows are the ones that actually decide it. If you need ANSI 300 or PN40, the single plate valve is not offered in them and the choice is made for you.
Below 232 PSI the single plate is the better buy on weight, cost and bore obstruction — unless slam is the specific problem you are solving.
Both work in any orientation, both fit between flanges, and both fail silently without a strainer in front of them.
Neither replaces a swing check on pressure drop. If you have the length and slam is not a concern, a swing disc lifting clear of the bore still costs you less head than any wafer type.

Dual plate check valves — the specification

As published. Blanks are marked, not filled.

Size range	1½" to 6" (DN40 to DN150)
Body style	Wafer — a ring clamped between two pipe flanges. It cannot terminate a run
Flange standards	ANSI 150# · ANSI 300# · JIS 5K · JIS 10K · PN10 · PN16 · PN40 — seven, and they are not interchangeable
Working pressure	Up to 300 PSI — a range across seven standards, not one rating
Material	Published as “Stainless Steel / CF8M”; the stocked castings read CF8 — 304 against 316
Discs	Two half discs, hinged on a shaft across the bore
Spring	Torsion spring wound round the hinge shaft, stainless
Orientation	Any, including vertical with flow downward — a spring closes it, not gravity
Flow direction	Follow the arrow. Fitted backwards, any check valve blocks the line
Length in the run	Almost none — the body sits between the flanges, against 356 mm for a flanged swing check at 6"
⚠ Dimensions	Not published — we measure a stocked valve on request
⚠ Bill of materials	Not published as numbered parts
⚠ Weight, test pressures, temperature	Not published
Catalogue	The manufacturer’s PDF
Fit upstream	A Y‑strainer. This valve fails silently, as every check valve does
Stock	Held in Malaysia or Singapore

Six kinds of check valve

All six are on this site. The dual plate wins on length and on slam.

Type	Length in the run	Slam	Pressure drop	Right when
Dual plate check	Almost none — wafer	Least	Moderate	Short runs, slam, or ANSI 300 / PN40.
Single plate check	Almost none — wafer	Low	Lower than dual	Lighter and cheaper, where PN16 is enough.
Swing check	356 mm at 6"	Most	Lowest — the disc lifts clear	You have the length and want least restriction.
Spring check	Short, threaded	Low	Higher	Small bore — 1/4" to 2" at 1000 PSI.
SAE flange check	Short	Low	Moderate	SAE flanged hydraulic pipework.
High pressure check	Short	Low	Higher	Pressure well beyond 300 PSI.

The two wafer types are the large‑bore answer. Between 1½" and 6", if the run is short or slam is a problem, it is dual plate or single plate. Below 1½", it is a spring check.
The swing check still wins on pressure drop. Nothing beats a disc that lifts entirely out of the bore. If you have 356 mm to spare and the pump does not trip hard, it is the cheaper and freer‑flowing choice.
None of them isolates. You still need a gate valve or a ball valve to shut the line deliberately — and on a wafer valve you need them anyway, since the flanges have to come apart to get it out.

Questions we get asked

The ones that come up on the phone.

What is a dual plate check valve?

A ring with two half‑discs in it, hinged on a shaft straight across the middle and held closed by a torsion spring. Forward flow folds the halves back like swing doors; when flow falls away the spring folds them shut. The body is a wafer — a thin ring with no bolt holes, clamped between two pipe flanges — so it takes almost no length in the run. 1½" to 6", up to 300 PSI, in seven flange standards.

Why choose it over a swing check?

Two reasons. Length: a wafer body sits between the flanges, where a flanged swing check at 6" needs 356 mm of pipe run to itself. Slam: two light half‑discs, spring‑assisted and travelling a short distance, close far more gently than one heavy disc swinging through 90° and waiting for the flow to reverse first. On long lines and high‑head pumps that is the whole argument. The cost is more pressure drop — the shaft, the spring and the disc edges all sit in the flow.

Which flange standard do I need?

Whichever your pipework is — and you must state it when you order. This range is offered in seven: ANSI 150 and 300, JIS 5K and 10K, PN10, PN16 and PN40. A 4" dual plate check valve is not one product but seven, and they are not interchangeable. The full list.

Is it really 300 PSI?

“Up to 300 PSI” is a range across seven flange standards, not a single rating. It plainly refers to the ANSI 300 and PN40 versions — a PN10 body cannot be 300 PSI. The manufacturer does not publish a breakdown by standard, so ask us for the rating of the one you are actually ordering and we will get it before you commit.

Is it 316 or 304?

The specification says CF8M, which is cast 316. The discs on the stocked valve are cast CF8, which is cast 304 — the marking is legible on both halves in the first photograph. On clean fresh water the difference is academic. On anything chloride‑bearing it is not, because 304 pits and the first thing pitting affects on a check valve is the seat face. Tell us if your duty is chloride‑bearing and we will confirm the grade for your exact size and flange standard. The full explanation.

Can I fit it upside down?

Yes. A spring closes it, not gravity, so it works in any orientation including a vertical run with flow downward — which a swing check valve cannot do at all. The one rule that still applies is direction: flow must follow the arrow, and fitted backwards any check valve blocks the line.

Can it sit at the end of a line?

No. A wafer body has no bolt holes of its own — it is held in place by the flange bolts passing either side of it. Take one flange off and the valve is no longer held. If it must terminate a run you need a lugged body, which is a different product; ask us.

How long is it? I need to check clearance.

No dimension table is published for this range — no face‑to‑face, no body outside diameter. Tell us the size and flange standard and we will measure a stocked valve, same day. The body outside diameter matters as much as the length on a wafer valve, because it has to sit inside the flange bolt circle without fouling the bolts.

Does it need a strainer in front of it?

Yes, as every check valve does. Debris caught between a disc and its seat holds one half fractionally open, and the valve then passes reverse flow while looking perfectly normal from outside. On a wafer valve you cannot even see the discs without taking the flanges apart. A Y‑strainer upstream is the single most effective thing you can do for it.

What sizes do you hold in stock?

1½" to 6" (DN40 to DN150), held in Malaysia or Singapore. Send the size, the flange standard, the fluid and — if slam is what you are solving — the line length and pump head. We will confirm availability, get the rating for your standard, and quote a landed price.

Catalogue

Direct PDF download — no form, no email address.

Dual plate check valves — wafer, 7 flange standardsAF Hydro · PDFPDF

Send the size and the flange standard

The flange standard is not optional on a wafer valve — this range is offered in seven and they do not interchange. Tell us which, plus the fluid and the line length if slam is the problem, and we will get the rating for your standard, measure a stocked valve, and quote a landed price. Stock in Malaysia and Singapore.

Get a quote Dual or single plate?