Drains and Supplies 
It’s fair to say that your water delivery system is the most used and most important system in your home. From the shower and toilet to the kitchen sink,
your water delivery system is a marvel of modern living. But have you ever thought: How does the water get to you?
The drains and supplies that help deliver your water are a well-planned and coordinated highway. The correct lines, valves, and drains with specific
measurements make this all possible.
Residential Plumbing Systems
All of the plumbing in a home (including bathrooms, laundry rooms, and kitchens) is tied to one common plumbing system. This is both the water supply and the sewage/waste system. The water you get when you turn on a faucet or flush a toilet arrives via municipal supply or well. The cold water comes in cold, and the hot water is supplied by a water heater, and it’s likely both pipes measure ¾”. The water supplies are then reduced to ½” branches and flow to the individual faucet. NOTE: Newer and larger homes often feature 1” main lines with ¾” supply lines that feed into bathrooms or whirlpools. Kitchen and bathroom sink faucets are designed to be installed to ½” water lines—through a ½” stop valve and 3/8” OD supply line (OD meaning Outside Diameter). And even though most bath and shower faucets are supplied by ½” water lines, larger whirlpool and custom showers have led to the introduction of the “high-flow” or “fast fill” whirlpool valves, which measure ¾”.
Even though they’re all designed to do the same job, not all drains are created equal.
- Material: Brass is the most preferred and trusted material for prolonged contact with water, but some drains are made from plastic.
- Finish type and quality: The drain finish usually matches the sink and may match the faucet. Special (i.e., more expensive) finish options can usually be ordered.
- Drain depth and quality: You can usually use any drain with any sink, but it’s easier and smarter to avoid cross-pollination and stick with the same brand.
Bathroom Drains and Supplies
Because high-capacity whirlpool faucets and custom shower systems often require large volumes of water and pressure, you’ll need to confirm that a few things meet your needs before installing and using one or both:
- The capacity of your water system measured in gallons per minute (GPM), especially if you’re on a well system.
- If you’re installing a large whirlpool, check your water heater capacity and the size of your water lines that feed your whirlpool faucets.
- For sanitary purposes, each individual plumbing fixture needs its own water trap (also known as a P-Trap) to bridge the fixture to the sewage system. NOTE: Different fixtures may have different size and type drains.
Speaking of P-Traps, tub and shower traps are installed beneath the floor and are installed when the plumbing system is installed. And toilets have built-in trapways.
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Bathroom Sink Drains 
All bathroom drains fit a standard 1 ¾” opening and usually have a 1 ¼” tailpiece. Nearly all faucets come with a pop-up drain, and sinks with overflows need one. Vessel sinks do NOT include overflows and require special order drains. Vessel, self-rimming, and drop-in sinks feature 1 ½” P-Traps with 1 ½” by 1 ¼” washers and 3/8” OD supply tubes. P-Traps can be made of plastic, rough brass, or chrome, and are usually already in place (a plumber can help install one if it’s not). Pedestal, wall hung, and console style sinks feature 1 ¼” P-Traps OR 1 ½” P-Traps with 1 ½” by 1 ¼” washers. Their 3/8” OD supply tubes can be made of metal or braided flex. Shut-off valves (also called stops) can be straight (installed through the floor) or angled (installed through the wall).
Tub Drains 
Moving to the tub and shower, tub drains (also called trip levers, waste and overflow, or trip waste) measure 1 ½” to fit standard 1 ½” P-Traps, and fit standard 14” to 16” deep tubs. They are NOT included with the tub faucet or tub itself, and must be ordered separately (usually from the same tub faucet manufacturer) and can typically match existing fixtures. Tub drains are normally already installed or installed by a plumber.
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Whirlpool and Soaking Tub Drains 
These drains are very much like your standard bathtub drain. They still measure 1 ½” to fit the standard 1 ½” P-Traps, and fit standard 17” to 26” deep tubs. They are NOT included with the tub or faucet and must be ordered separately to match the whirlpool finish and monochromatic tub trim OR to match the faucet and metallic trim kit. These can usually be purchased from the same faucet or whirlpool manufacturer. Finally, these drains are normally already installed or installed by a plumber. The one difference is that whirlpool tub drain styles can be lever or twist-and-turn cable operated.
Leg Tub Drains 
These measure 1 ½” OD brass and are finished on all sides to match the faucets. They come with stopper and chain, and mount through the floor with an escutcheon. Be sure to check the manufacturer tub specs to make sure all measurements match up.
Shower Drains 
These fit standard 3 ¼” opening and connects to a 2” P-Trap. Most shower bases come with a standard chrome or stainless steel drain (NOTE: Kohler bases come WITHOUT the drain). For a custom tiled-in shower base, you may need to order a special shower drain or an optional finish drain plate. Once again, P-Traps are normally already installed or installed by a plumber.
Shower and Whirlpool Supplies 
Most shower faucets come with ½” supply connections that are either copper (cc or swt) or threaded (IPS). These supplies connect to the plumbing system, and some larger Hi-Flow and thermostatic valves come with ¾” connections. Most whirlpool faucets come with ¾” supply connections that are either copper (cc or swt) or threaded (IPS). Some larger high-flow and thermostatic valves come with ¾” connections.
Kitchen Drains and Supplies
While your bathroom can feature various fixtures for a number of purposes (and, as a result, different drains, supplies, and measurements), your kitchen drain is pretty textbook by comparison. It’ll fit a standard 3 ½” opening and connect to a standard 1 ½” tailpiece. The only guesswork will come with the drains—since some sinks come with drains, but most DO NOT. Check the sink’s specs for more details.
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Kitchen and Bar Supplies and P-Traps 
Since the P-Traps will be hidden in a kitchen cabinet, style and finish won’t be too important. So just make sure you get the best quality you’re most comfortable with. P-Traps measure 1 ½” and are made of plastic, chrome, or rough brass. The OD supply tubes for the P-Traps measure 3/8” and can be plastic, metal, or braided. All kitchen sink faucet supply connections will be either ½” male thread or 3/8” OD copper tubing.
Faucet hole covers
Faucet Hole Covers are designed to conceal extra holes in the sink and come in various finishes. Finally, dishwasher air gaps are essential since they separate the dishwasher drain from potable (drinkable) water, and prevent drain water from being siphoned back into your water supply. Plus, they’re a code requirement in certain areas, so they’re good to have.
Bar sinks
Bar Sinks are smaller than your standard kitchen sink, so the drains will be smaller, as well, and are sometimes called “Junior Basket Strainers.” Bar drains fit a standard 2” opening and connect to the P-Trap with either a 1 ¼” or 1 ½” tailpiece. The drain will have either a standard grid cover or feature a “pull-out” plug. Some bar sinks use a conventional 3 ½” sink drain opening. Once again, check the specs for details. That’s the long and short (mostly long) of kitchen and bathroom drains and supplies. If you have questions regarding specific parts or manufacturers, feel free to contact our knowledgeable customer service staff. As always, Happy Home Improving!
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