Y-Strainers and Basket Strainers: Mesh, Orientation and Pressure Ratings

Choosing a strainer body, reading a mesh number and installing the thing the right way up. Every pressure and material figure below comes from the manufacturer submittal sheet for a product we stock.

Y-strainer and wye strainer are the same device

Wye is the letter Y written out, the way tee is T written out. There is no difference in the fitting, the standard or the price, and manufacturers use both spellings in the same catalogue. If a submittal says wye strainer and the plan says Y-strainer, nothing has changed.

The name describes the shape. The body is a run of pipe with a leg branching off at roughly 45 degrees, and the screen sits in that leg. Flow enters, passes through the screen from the inside out, and leaves clean. Debris drops into the pocket at the bottom of the leg and stays there until somebody opens the cap or the blowoff plug.

Orientation is the mistake that costs the job

A Y-strainer only works with gravity helping it. On a horizontal line the screen leg must point downward, so the debris it catches falls into the pocket and stays out of the flow. Installed with the leg pointing up, the strainer traps material against the screen until flow pushes it back into the line the moment the pump cycles. It looks installed, it passes the pressure test, and it is doing nothing.

On a vertical line, flow has to run downward. The Legend cast iron sheet puts it plainly: the strainer can go horizontal or vertical, the cap must point down, and in the vertical position the media must flow downward. A vertical riser with upward flow has no strainer position that works.

Leave clearance below the cap. The screen has to come out for cleaning, and the removal length is roughly the dimension the submittal calls B. A strainer tucked hard against a joist is a strainer nobody will ever service, which makes it a restriction rather than a protection.

Y-strainer or basket strainer

Both hold a screen in the line. They are sized and serviced differently, and the choice usually comes down to how often the screen will need cleaning.

For plumbing and hydronic work in a building, the Y-strainer is almost always the right answer. It costs less, takes no headroom and the debris load on a piped system is a construction problem, heaviest in the first month and light after that. Basket strainers earn their cost where solids arrive continuously and somebody is cleaning the screen on a schedule.

A note on our own catalogue, because the search term is ambiguous: the 36 products we list as basket strainers are sink drain baskets, the fixture part that fits a kitchen or bar sink. They are not pipeline basket strainers. If you need an inline basket strainer, call us rather than ordering from that category.

Mesh is the real decision, not the body

The screen is a separate part from the strainer, and on the bronze bodies it is available in several grades for the same fitting. Mesh counts the openings per linear inch, so a higher number is a finer screen. The actual opening also depends on the wire diameter, which is why the figures below are nominal.

Two things in that table surprise people. First, the perforated strainer fitted to the 2-1/2" and 3" bodies is coarser than the 20-mesh screen on the small sizes, not finer. On a 3" line the flow area matters more than catching fine grit, and a fine screen at that size would blind over and starve the pump. Second, going finer is not free: an 80-mesh opening is about a quarter the width of a 20-mesh opening, so it stops far more material and blinds over far sooner. Specify the coarsest screen that protects whatever is downstream, and no finer.

Screens are consumable and replaceable. A screen that has been cleaned several times has usually been deformed at least once, and a deformed screen passes debris around its edge rather than through it. If the downstream equipment starts fouling on a system that used to run clean, pull the screen and look at the seal face before blaming anything else.

Body material sets the pressure and temperature limit

Three bodies cover almost every building application, and the spread between them is wider than the price difference suggests.

The press body also has a tubing restriction that has nothing to do with pressure. Legend specifies it for ASTM B88 type K, L and M hard drawn copper and explicitly not for annealed soft copper coil, because soft tubing deforms under the jaw instead of holding the seal geometry.

Cast iron carries the highest numbers here and is the cheapest of the three, which looks like an easy decision until the line is potable. Cast iron is not a lead-free potable material. On drinking water the no-lead bronze body is the one carrying the NSF/ANSI 61 listing, and that listing is what an inspector checks.

The blowoff plug

Every one of these strainers ships with a square-head closure plug in the bottom of the cap. It is there so the pocket can be flushed under pressure without pulling the screen: crack the plug, let the trapped debris blow out with the line still running, close it. On a system commissioned recently that is a five minute job that can be done monthly, against a shutdown to open the cap.

Replacing the plug with a small ball valve and a hose nipple is common and worth doing on anything that will be flushed more than twice. The plug tapping is sized with the body: 3/8" on the small bronze strainers and 1/2" from 1" up, on the Legend bronze pattern.

What we stock

16 standalone Legend Y-strainers, in 6 sizes from 1/2" through 2", every one supplied with a 304 stainless 20-mesh screen and a square-head blowoff plug.

Sizes in stock: 1/2" (3), 3/4" (2), 1" (3), 1-1/4" (3), 1-1/2" (3), 2" (2).

Alongside those, 2 Webstone press full port ball valves with a hose drain and an integral Y-strainer, in 1/2" and 3/4". One body does the shutoff, the drain and the strainer, which on a tight boiler near-piping is often worth more than the serviceability of three separate fittings.

Not stocked, and worth asking about before you design around them: cast iron and 316 stainless bodies, flanged bodies, the 1/4", 3/8", 2-1/2" and 3" sizes, and replacement screens in 40 and 80 mesh. Legend builds all of them and we can bring them in.

Browse the catalog

• Y-Strainers
• Legend Valve
• Ball Valves
• Relief Valves
• Backflow Preventers

Valve types, pressure ratings and end connections are covered in our valve reference guide. Need a mesh, a size or a body material that is not listed? Call +1 (623) 307-5144 or email info@thehousesupplier.com.