The short answer: Use both. Standard plumbing practice for residential systems is to use 3/4-inch PEX for the main trunk lines (and the water heater feed), and then step down to 1/2-inch PEX for individual fixture branches (like sinks, toilets, and standard showers).
When deciding between 1/2-inch and 3/4-inch PEX for your plumbing project, the golden rule is use 3/4-inch for mains/trunks and 1/2-inch for individual fixture branches. One size does not replace the other; they are designed to work together to balance water pressure and flow.
The "135-degree rule" in plumbing states that the total (aggregate) horizontal change in direction for a drainage pipe—specifically trap arms—cannot exceed 135 degrees between the P-trap and the vent. Exceeding 135 degrees (such as using three 45-degree bends or a 90 and two 45s) requires a cleanout because sharp turns hinder flow and cause clogs.
If your water supply line is up to 250 feet, the 3/9″ PEX pipe is already suitable to grant sufficient water pressure. Meanwhile, for a 350-feet line, the 1/2″ tubes are the best fitting, and for a 500-feet line, a 3/4″ PEX piping will perform much better.
longer a pipe run, the larger the diameter the better for water volume which can translate into higher pressure at the point of use. 3/4" for bibs every time.
The wrong size could mean you might not have enough water pressure to get the job done properly. A 5/8” vs. 3/4" hose can mean a vast difference in the amount of water pressure your hose generates. Pressure is something you have to consider, especially if you intend to use your hose for outdoor cleaning projects.
Standard outdoor spigots (also known as hose bibbs or sillcocks) feature two primary measurements: the pipe connection size to your home's plumbing, and the hose attachment size.
Despite these benefits, some insurance companies have raised concerns about PEX plumbing, particularly regarding older installations: Historical issues: There were class action lawsuits against PEX manufacturers due to premature failures at connection points, resulting in leaks and flooding in some cases.
The most common PEX sizes in residential plumbing are 1/2-inch and 3/4-inch.
3 Plumbing Pipe Materials You Don't Want In Your Home
Here are the most common plumbing code violations you might not even realize you have—and why they matter.
a waste pipe must be layed so it has a fall of 1 in 4 (mcguires rule).
To protect your plumbing and the environment, you should never put fats, starches, harsh chemicals, or solid waste down your drains.
Running 3/4" piping from the 1/2" feed will slightly decrease the pressure loss, meaning you'll get more pressure at your fixtures, but the difference will probably be very small. Most of the pressure loss will have already occurred in the 1/2" line before it reaches your house.
Generally, you can budget around $2 to $6 per square foot for a PEX repipe. So, for a 2,000-square-foot home, you might estimate a cost between $4,000 and $12,000. You can also refine your estimate by counting your plumbing fixtures.
The larger the distance from the manifold to the tube fixture, the wider the PEX pipe should be. You can opt for a ⅜-inch line for lengths up to 250 feet. If you want to adequate water pressure up to 350 feet, opt for a ½-inch line. A 500-foot line will work better with a ¾-inch PEX tubing system.
Use 3/4-inch PEX for main water lines and high-demand branches. Use 1/2-inch PEX for individual fixture supply lines (sinks, toilets) and shorter branch runs. The 3/4-inch pipe provides higher volume and prevents pressure drops, while the 1/2-inch pipe maintains proper pressure at the faucet and reduces wait times for hot water.
PEX pipe is more resistant to bursting in freezing conditions than metal piping. Because it's flexible, PEX tubing expands rather than splitting, minimizing costly repairs. A long product lifespan reduces cost associated with it, increases customer satisfaction and lessens waste.
For a 12one-half12-inch PEX pipe, you will typically need to drill a 34three-fourths𝟑𝟒-inch, 78seven-eighths𝟕𝟖-inch, or 𝟏𝟑𝟖-inch hole, depending on your installation method:
However, recent failures and the lawsuits that have followed those failures lead to the idea that PEX plumbing systems aren't as good as once assumed. PEX systems can fail in either the pipe or in the fitting. The most notable failure occurs when the fittings fail and water starts leaking and causing visible damage.
Did you know that PEX piping is used in about 60% of new construction projects to date? This makes it a prevalent material used in new buildings.
PEX (cross-linked polyethylene) plumbing typically lasts between 40 and 50 years. Manufacturers often provide warranties of 25 years, but when properly installed and maintained within standard water pressure and temperature limits, the tubing itself often exceeds a half-century of use.
For residential use, 58five-eighths𝟓𝟖-inch garden hoses are significantly more common. They offer the ideal balance of water flow and maneuverability for most households.
When shopping for a toilet supply line, the 3/8-inch size is the modern standard for residential shut-off valves, while 1/2-inch is usually reserved for older, existing plumbing. For the toilet end, however, both require the exact same 7/8-inch connector to attach to the fill valve under the tank.