Valve Types, Pressure Ratings and End Connections
A quick reference for choosing between valve types, reading a pressure rating and matching end connections. Every rating and material below is taken from the manufacturer data on the products we stock, not from a generic table.
How to read a valve pressure rating
Bronze and brass valves carry two numbers. WOG stands for Water, Oil, Gas and is the non-shock cold working pressure. SWP stands for Steam Working Pressure and is the limit for saturated steam, which is always the lower of the two because steam carries heat that softens the body and the seat.
A valve marked 150 SWP – 600 WOG will hold 600 psi of cold water but only 150 psi of steam. If a line ever sees steam, the SWP number is the one that governs. A valve with no SWP rating is not rated for steam at all.
These are the ratings on the valves we currently stock:
| ANSI / pressure rating | Products in stock |
|---|---|
| 600 WOG | 22 |
| 125 SWP – 200 WOG | 16 |
| 150 SWP – 300 WOG | 10 |
| 250 WOG | 10 |
| 200 psig, 250 psig, 250 psig @ 250 Degrees F | 10 |
| 600 WOG – 150 SWP | 9 |
| 300 SWP – 1000 WOG | 6 |
| 175 psi | 6 |
| 250 psig @ 250 Degrees F | 4 |
Ball valve vs gate valve
Both are shutoff valves and neither is meant for throttling, but they fail in different ways and that decides which one belongs in a given line.
| Ball valve | Gate valve | |
|---|---|---|
| Operation | Quarter turn, 90° | Multi-turn handwheel |
| Time to close | Instant | Slow — several turns |
| Pressure drop | Near zero when full port | Near zero when fully open |
| Throttling | No — partial opening erodes the seat | No — partial opening erodes the disc and seat |
| Typical rating here | 600 WOG – 150 SWP | 125 SWP – 200 WOG |
| Seat material | RPTFE or PTFE | Bronze, metal to metal |
| Common failure | Seat wear from throttling | Stem packing leak; wedge sticks after years open |
| Best for | Isolation you actually operate | Isolation you rarely touch, and larger bore at lower cost |
The practical rule: if someone will turn it, use a ball valve. If it is a main that gets opened once at commissioning and closed once a decade later, a gate valve costs less in the larger sizes. Water hammer is the one argument against ball valves — a quarter turn closed fast on a long run of moving water can spike pressure hard enough to split a fitting.
Examples from stock
| SKU | Type | Rating | Port | Seat / disc | Price |
|---|---|---|---|---|---|
| MLWV-BA-475B-12 | Ball | 600 WOG | Full | PTFE | $24.64 |
| MLWV-BA-485B-12 | Ball | 600 WOG | Full | PTFE | $24.64 |
| MLWV-BA-475B-14 | Ball | 600 WOG | Full | PTFE | $32.85 |
| MLWV-105-12 | Gate | 125 SWP – 200 WOG | — | Solid Wedge | $88.94 |
| MLWV-105-34 | Gate | 125 SWP – 200 WOG | — | Solid Wedge | $108.15 |
| MLWV-1151-12 | Gate | 150 SWP – 300 WOG | — | Solid Wedge | $134.61 |
Full port vs standard port
A full port ball valve has a bore equal to the inside diameter of the pipe, so it adds almost no restriction. A standard port valve has a bore one nominal size smaller, which is cheaper and perfectly adequate for isolation, but it does cost you head.
It matters on pump suction lines, on long runs where head is already tight, and anywhere a cleaning ball or camera has to pass. It does not matter on a fixture stop.
| Port | Bore | Products in stock |
|---|---|---|
| Full | Equal to pipe ID | 45 |
| Standard | One nominal size smaller | 6 |
Check valve types
A check valve allows flow one way and closes on reversal. The body style decides where it can be mounted and how much pressure it needs to open.
| Body style | Mounting | Cracking pressure | Notes |
|---|---|---|---|
| Horizontal swing | Horizontal lines only, cap up | Very low | Lowest pressure drop. Relies on gravity, so orientation is not optional. |
| Y-pattern swing | Horizontal or vertical up flow | Low | Angled seat keeps the disc off the flow path. |
| Spring loaded lift | Any orientation, including vertical down | Higher | The spring closes it, not gravity. Use where a swing check cannot sit level. |
| Dual check | Any | Higher | Two checks in series. Used for backflow protection on a service line. |
Examples from stock
| SKU | Body style | Rating | Seat | Disc | Price |
|---|---|---|---|---|---|
| MLWV-548T-12 | Spring Loaded Lift | 250 WOG | Bronze | TFE | $64.89 |
| MLWV-1548T-34 | Spring Loaded Lift | 250 WOG | Bronze | TFE | $86.55 |
| MLWV-548T-34 | Spring Loaded Lift | 250 WOG | Bronze | TFE | $86.55 |
| MLWV-1548T-100 | Spring Loaded Lift | 250 WOG | Bronze | TFE | $117.80 |
Seat and disc materials
The seat is the part that actually seals, and it is the first thing to fail. Material sets the temperature ceiling and the chemical compatibility.
| Seat | In stock | Where it belongs |
|---|---|---|
| PTFE | 33 | General service. Clean seal, low friction, limited above roughly 400°F. |
| RPTFE | 15 | Glass or carbon filled PTFE. Higher pressure and better creep resistance. |
| Bronze | 36 | Metal to metal. Tolerates heat and particulate; will not seal bubble tight forever. |
| Viton | 6 | Elastomer for oils and fuels where PTFE is not the right chemistry. |
| Cu-Ni | 6 | Copper nickel, for seawater and brackish service. |
End connections
| Connection | In stock | Note |
|---|---|---|
| Threaded (NPT) | 61 | Serviceable with a union. Tapered thread seals on interference, so use sealant and do not over-torque bronze. |
| Solder (sweat) | 21 | Permanent. On ball valves, open the valve and pull the seat if the manufacturer calls for it before applying heat. |
| Press | 10 | No flame. Requires the matching jaw and a witness mark check after crimping. |
| Press x hose | 4 | Press inlet with a hose thread outlet, typical on boiler drains. |
Backflow preventers, PRVs and T&P relief valves
These three get confused because all of them are safety devices on a water line, but they answer different questions.
| Device | Protects against | Set by |
|---|---|---|
| Reduced pressure principle (RP) backflow preventer | Contaminated water flowing back into potable supply, under back pressure or back siphonage. Highest hazard class. | Fixed — two checks plus a relief port that dumps if either fails |
| Double check backflow preventer | Same direction of failure, lower hazard class. No relief port. | Fixed |
| Pressure reducing valve (PRV) | Street pressure higher than the building can take. Protects fixtures and water heaters from constant over pressure. | Adjustable, typically 15–75 psi |
| Temperature and pressure (T&P) relief valve | A water heater that overheats or over pressurizes. Opens on either condition, whichever hits first. | Fixed at manufacture — commonly 150 psi and 210°F |
TP1100A-4C-150C the 4 is the length of the thermostat element in inches and the 150 is the relief pressure in psi. The inlet is 3/4 inch. Ordering by the model number alone is how a 3/4 inch valve gets bought as a 4 inch valve.Examples from stock
| SKU | Type | Max pressure | Max temperature | Price |
|---|---|---|---|---|
| WILK-TP1100A-4C-125C | Temperature and Pressure Relief Valve | 125 psi | 210 deg F | $58.44 |
| WILK-TP1100AE-3C-150C | Temperature and Pressure Relief Valve | 150 psi | 210 deg F | $60.39 |
| WILK-TP1100A-4C-150C | Temperature and Pressure Relief Valve | 150 psi | 210 deg F | $62.34 |
| WILK-P1000AXL-125C | Pressure Relief Valve | 125 psi | 250 deg F | $75.97 |
| WILK-P1000AXL-150C | Pressure Relief Valve | 150 psi | 250 deg F | $75.97 |
Shop by line
Specification sheets and installation manuals are on the individual product pages. For a submittal we do not have published, call +1 (623) 307-5144 or email info@thehousesupplier.com.
Ratings and materials shown are from manufacturer published data for the products in our catalog. Always confirm against the specification sheet for the exact model before specifying.