Moving kitchen sink plumbing is a significant home renovation. Before starting, ensure safety by locating and shutting off the main water supply to the home. Power to the kitchen disposal circuit must also be deactivated at the main electrical panel. This project involves altering both pressurized supply lines and gravity-fed drain systems, making it more involved than a simple repair or fixture replacement.
Essential Planning and Code Requirements
Before cutting into walls or pipes, thorough planning is required, starting with researching local building and plumbing codes. Jurisdictions often mandate permits for alterations to the Drain, Waste, and Vent (DWV) system. Failing to secure proper authorization can lead to costly rework later. These regulations govern acceptable pipe materials, minimum pipe diameters, and the precise geometry of the drainage system. Planning also involves assessing the structural elements of the wall cavity and floor space where the new plumbing will run.
Determining the location of the existing main drain stack is necessary, as the new drain line must tie into this vertical pipe. The code requires a consistent downward pitch, or slope, for the drain line’s entire run. Plumbing standards require the drain pipe to drop at a rate of one-quarter inch for every foot of horizontal travel. This slope ensures efficient waste removal via gravity; without it, solids can accumulate, leading to blockages in the new system.
Relocating Water Supply Lines
Relocating the hot and cold water supply lines involves extending the pressurized system from its original connection point to the new sink location. Many choose Cross-linked Polyethylene (PEX) tubing because its flexibility simplifies routing through wall studs and floor joists without numerous elbow fittings. Copper tubing requires soldering and specialized tools to make secure connections, adding complexity. Once the material is chosen, existing lines are cut, and new lengths are spliced in using appropriate fittings, such as crimp rings for PEX or sweat fittings for copper.
The new supply lines are routed horizontally or vertically through the wall cavities. They must be protected from drywall screws by running them through the center of the studs or using metal protective plates. Running these lines parallel to the floor joists often provides the most direct path to the new sink location. The process concludes with installing new shut-off valves, commonly known as angle stops, which isolate the sink faucet and allow for future maintenance without affecting the entire house water supply.
Extending and Reconfiguring the Drain and Vent System
Reconfiguring the DWV system is the most complex part of moving the sink, as its function relies on gravity and atmospheric pressure balance. The new drain line must be connected to the existing vertical drain stack using a sanitary tee fitting. This fitting allows a smooth transition from a horizontal branch line into the vertical stack without disrupting the flow. The required one-quarter inch per foot slope must be maintained across the entire length of the new drain pipe for the system to function correctly.
Proper venting is necessary for the DWV system, preventing negative pressure from siphoning water out of the P-trap. The P-trap, the U-shaped pipe under the sink, holds a water seal that blocks sewer gases from entering the living space. If the drain line is not adequately vented, rushing water creates a vacuum, pulling the water seal out and compromising the barrier. Connecting the new drain line to the existing vent stack is the most reliable method, allowing air to enter the system and equalize pressure.
If the new sink location is too far from the existing vent stack, local codes may allow the use of an Air Admittance Valve (AAV). An AAV is a one-way mechanical valve that opens when water drains to allow air into the system, preventing the vacuum effect. It remains closed otherwise to contain sewer gases. While an AAV simplifies installation by eliminating extensive vent piping, its use is restricted by some plumbing codes because it relies on a mechanical part that can fail.
Regardless of the venting method, the new fixture must be located within a specific distance from the vent connection point for effective pressure equalization. Using fittings like long-sweep elbows instead of tight 90-degree turns further ensures smooth waste flow and reduces the chance of blockages.
Final Connections and System Verification
With the supply and DWV systems extended and secured, the final connections involve installing the tailpiece and the P-trap assembly beneath the sink basin. All connections, especially threaded fittings, should be sealed using pipe thread compound or Teflon tape to ensure a watertight seal. After the physical plumbing is complete, a two-part verification process is necessary to test the integrity of the work before closing the wall cavity. This verification begins with a pressure test of the supply lines.
The supply lines should be pressurized and monitored for several hours to confirm no leaks appear at the connection points, angle stops, or splices. Following the pressure test, the drain system requires rigorous leak testing. This is achieved by filling the sink basin completely with water and then pulling the drain plug to simulate maximum flow conditions.
The entire drain assembly, including the P-trap, fittings, and the connection to the main stack, should be visually inspected during this rapid drainage. Only after both the pressurized and gravity-fed systems have passed their tests can the wall cavity be safely repaired and finished.