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Bathtub Plumbing Basics Explained

What Everyone Should Know About Bathtub Plumbing

Most people don’t give too much thought to their bathtub or how it works until a problem pops up. It won’t drain properly, it won’t stay full, or - even worse - an irreplaceable piece of jewelry goes down the plug. It pays to know a little bit about how bathtubs work, though, just as it pays not to take it for granted. After all, what better place to bathe a mud-covered dog, teach a 4-year-old the importance of hygiene, or simply unwind with a nice hot bubble bath? 

This article will explain how bathtubs work and how they fit into the home’s overall plumbing system.

How a Home’s Plumbing System WorksPlumber working on plumbing system

The plumbing system in a home is actually made up of two separate, yet interdependent systems. One supplies freshwater, and the other removes wastewater. The main supply pipe runs into the home through the water meter, then splits into two networks of pipes: hot and cold. The cold water supply network goes immediately to every faucet and fixture throughout the home, while the hot water supply network passes through the water heater along the way. The supply system relies on pressure to get the water where it needs to go.

The wastewater removal system, on the other hand, relies on gravity to do its job. Every drainage pipe leads down, whether the house utilizes a septic tank or the municipal sewer system. Although gravity is the primary force behind waste removal, it wouldn’t work without a couple of other vital components. Ever notice those little pipes sticking straight up out of the roof of a house? Those are vents that provide airflow to the drain pipes. Without them, the used water wouldn’t drain properly (think of how a person can hold the liquid in a plastic straw by plugging one end of it with their finger).

Bathroom Plumbing and Drain TrapsBathroom

The other crucial component of the drainage system is the trap. While every drain in the house has a trap, the bathroom contains a few different kinds of traps. The designs of traps may differ slightly, but the principle is always the same. The most common of these is the P-trap. This is a U-shaped section of pipe directly under the sink drain. When water flows down the drain, some remain stuck in this curved lower portion of the pipe to create a sort of natural seal. This water seal keeps sewer or septic gas from creeping up through the drain.

Toilets, on the other hand, have built-in traps. The curving shape of the trapway can typically be seen protruding from the toilet’s base, just below the tank. In this case, the water in the toilet bowl itself provides the vital seal. Some older bathtubs have what’s known as a drum trap, a small metal canister which fills to create a water seal and traps whatever debris has gone down the drain. These have mostly been replaced with P-traps, as they require periodic manual cleaning to remove the buildup of hair and dirt. Yuck!

Specifics of Bathtub PlumbingMan Caulking a Bathtub

Like other fixtures in the house, a bathtub has two supply pipes, typically made of copper, which meet at the faucet - one for hot water and one for cold. Water flow at the tap is controlled by either a compression valve or a cartridge valve. Compression valves involve two separate handles or knobs, each controlling either the hot or cold water. Cartridge valves involve only one handle or knob which controls flow and temperature simultaneously.

Every bathtub has two drains - a waste drain and an overflow drain. These drain pipes, usually made of PVC, join above the trap, before they reach the main drainpipe. The waste drain can be opened or closed with a trip lever, usually located at the overflow drain, which raises or lowers either a pop-up stopper in the drain mouth or a cylindrical brass plunger inside the drainpipe itself. 

Because bathtub plumbing is often built into the wall or floor and not easily accessible, repairs can be difficult. If serious plumbing issues are present in this area of the bathroom, the safest bet is to call a reputable local plumber.

About Lambert Plumbing & Heating, LTD

Lambert Plumbing & Heating, LTD has been proudly serving Vancouver, British Columbia, since 1977. They are a Canadian-born, community-oriented company, offering up-front pricing, 24/7 service, and a 100% guarantee on all their services. Make sure to give them a call for any bathroom plumbing issues that may arise!