Home Plumbing Systems

©Don Vandervort, HomeTips

A home’s plumbing systems are a broad network of water and gas supply pipes, drain-waste-vent plumbing, and more.

An expert overview of home plumbing systems, including water supply, drain-waste-vent, and more.

If you have ever camped in the great outdoors, you have probably been reawakened to the joys of modern plumbing. By going without running water, a hot shower, or a flushing toilet, you can fully appreciate how important these are to daily life.

A home’s plumbing system is a complex network of water supply pipes, drainpipes, vent pipes, and more. Because plumbing is complicated and one of the costliest systems to repair or install in a home, it pays to understand how the system works.

Understanding the fundamentals of a plumbing system allows you to better understand the types of problems that occur or, if you’re planning a remodel or new home, it helps you design a system that will work properly and pass plumbing codes.

Regarding planning for major plumbing work: A properly designed system will deliver water to the various faucets, fixtures, and water-using appliances efficiently and carry away waste water without clogs. Second, it may save you money. By planning wisely, you can often reduce the overall plumbing expense significantly by locating bathrooms, kitchens, or laundry rooms near one another so that they can share parts of the system.

Several different systems make up a house’s plumbing. Fresh water is delivered to a home through water supply pipes from the utility or a well and is then distributed to sinks, toilets, washers, bathtubs, and related fixtures. The drain-waste-vent system carries away used water and wastes to sewers or septic tanks. Natural-gas plumbing delivers this fuel to gas-burning cooktops, furnaces, water heaters, and clothes dryers. For information on water heaters, see Water Heaters & Dispensers.

Water Supply System

A home’s water supply system routes municipal water from the street to your house, where it branches out to deliver the water to faucets, showers, toilets, bathtubs, and appliances such as the water heater, dishwasher, and washing machine.

water-supply-service-diagram©Don Vandervort, HomeTips

Water System Meter & Valve

The equipment for this delivery and distribution is essentially a system of water pipes, fittings, service valves, and faucets. These pipes and other fittings are commonly made of plastic, copper, or galvanized iron. The pipes range in diameter from 1/2 inch to 4 inches or more.

Drain-Waste-Vent System

DWV-System-vents-drains©Don Vandervort, HomeTips

Typical Vents & Drains in Home Plumbing

Though it isn’t one of the most glamorous parts of a house, the drain-waste-vent (DWV) system is one of the most crucial. The job of the drain-waste part of the system is to carry waste water and sewage from sinks, bathtubs, showers, toilets, and water-using appliances such as dishwashers and washing machines and deliver those wastes to the septic tank or public sewer.

The vent system—part of the plumbing that is usually less well known to most homeowners—is connected to the drain-waste piping, and its job is to ventilate sewage gases so they don’t build up in the house. The vent system also helps drainpipes maintain the right pressure for proper drainage.

The pipes of the DWV system are usually out of sight, hidden in the walls, beneath the floors, and in the attic. But when the system ceases to do its job properly, it is hardly out of mind. Clogged drains are among the most common problems that occur in a DWV system.

Kitchen Plumbing System

kitchen-sink-plumbing©Don Vandervort, HomeTips

Kitchen Sink Plumbing Diagram

If you’re reading this section, the chances are pretty good that either 1) you’re having problems with the pipes or drains in your kitchen or 2) you’re considering (or are in the midst of) a kitchen remodeling project that involves dealing with the pipes in the floor and walls. You’ll find help with both of these kinds of issues here, where we look at planning, installing, and caring for plumbing with a focus on the kitchen.

Most kitchens have a fairly simple plumbing setup that includes hot and cold water supply lines to the faucets; a waste line for the sink (or sinks); and, for kitchens with a gas range, a gas supply pipe. Many kitchens also have hookups for a dishwasher, disposer, ice maker, and/or instant hot water, but these are generally tied in to the sink’s plumbing.

For more about kitchen plumbing, refer to the Appliances section.

bathroom-sink-plumbing-diagram©Don Vandervort, HomeTips

Bathroom Sink Plumbing Diagram

Bathroom Plumbing System

Sinks, showers, bathtubs, and toilets—bathrooms are all about plumbing. The plumbing in a bathroom must handle water delivery to and waste removal from all of these fixtures in an organized, efficient, leak-free manner.

Two plumbing systems are needed to handle a bathroom’s plumbing needs: water supply and drain-waste-vent.

Water supply plumbing delivers hot and cold water to the sinks, tub, toilet, and shower. This system originates at the municipal supply or other fresh water source, goes through the meter, and is delivered to the house. At the water heater, it splits into two lines—one that carries cold water and the other that delivers hot water from the water heater to the fixtures that require it.

The drain-waste-vent system collects waste water from fixtures and waste from toilets and delivers them to the sewer or septic system. Near each of the sinks, tubs, showers, and toilets, vent pipes exhaust sewer gases up and out the roof and provide air pressure so wastes can flow freely.

For information on how to buy, install, and care for bathroom fixtures, use the HomeTips search box to specific searches.

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Join the Conversation

  • my drains in most of the house are omitting sewer gases

    • Don

      Sinks, showers, and tubs have a P-trap that fills with water to prevent sewer gasses from coming up through the drain. Floor drains have a trap, too, but this can dry out if they rarely get water in them. A quick answer is to put about a quart of water in each drain to refill the trap. This should block the gasses. Then look-up info on trap primers and trap sealers that help prevent this from happening.

  • tsc

    When we flush the toilet it always needs plungering, no matter was is in the bowl.

  • Noe Galindo

    My toilet and shower tub are both clogged what can I do. Water leaves but very very slow

    • Don Vandervort, HomeTips

      There is probably a clog in the drain pipe beyond where the shower drain meets the toilet’s drain pipe.

  • Tommy Smith

    I recently added a shower tray to the bathroom in my flat but the bath is draining into it. Can’t find anything online except issues with clogged pipes but mines are all new. The waste water pipes all run above the floor clipped to the wall with arrangement as follows:

    Left hand wall:
    90mm fast flow shower drain (80mm high) -> 2m 40mm pipe -> elbow (60mm high) -> connected to
    Back wall:
    0.3m 40mm pipe – T piece -> 0.7m 40mm pipe -> T piece -> 0.7m 40mm pipe (40mm high on exit to drain pipe)
    The 1st T piece on the back wall comes back to the center drain u-bend on my bath 140mm above the floor and the second is reduced to 32mm pipe to the sink drain.

    So basically it runs along two walls with a drop of 40mm in 40mm pipes. The T pieces are angled correctly but the bath water chooses to run back up the pipe off the T piece and into the shower tray. Is there a better arangement for these pipes and would changing my bath waste pipe to a 32mm slow down the drainage enough to stop the back flow? Wet wall due to be fitted but everything is on hold till I sort this out. Please help!

  • Des Sanders

    Hello there, we are living on a small bush property and are having trouble with our kitchen drain. The sink currently drains (underground) into a 44 gallon drum, but even though this has many holes drilled into it, it continually clogs up. We are trying to avoid installing a septic system; have a compost toilet and all other grey water drains to a small system of ponds. We don’t have town water or sewerage and are interested in any “green” solutions that might work! I presume a fat build up is causing this clogging of the sink, but don’t know what to do/buy to prevent this! Any ideas would be appreciated.

  • Well shared! I must say maintain home drainage systems is a very important factor. If the time to time maintenance is not done, then we have to face problem in long run. There might be some major blockage in the drainage system. Thanks for sharing useful information.

  • John Simpson

    Maintenance of home based pipe systems is very important, I have been installing and maintaining these for years as a plumber and I have seen so many leakages and hugely expensive incidents come about as people simply don’t maintain their home pipe and fittings. I am on a mission to try and teach people at least the very basics of pipe maintenance in the home. Thanks for a great article, I will definitely use this going forward. If anyone has any further information to share on home plumbing then I would love to hear it and share it around. I found a site here with some easy to follow tips for maintaining and properly caring for pipe systems, as well as some instruction for replacing broken parts and cleaning parts for people who have a bit more experience than just a novice.

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