Plumbing a dishwasher involves connecting it to both a hot water supply line and a drain line, ensuring proper water intake and waste disposal for efficient cleaning. This process typically requires specific fittings and careful attention to connections to prevent leaks and ensure proper drainage.
Essential Components for Dishwasher Plumbing
A dishwasher requires two primary plumbing hookups to function correctly:
- Water Supply Line: This line delivers hot water to the dishwasher. Dishwashers are connected to the hot water line because they all use hot water during washing cycles to effectively clean dishes and sanitize them.
- Drain Line: This line carries the dirty water out of the dishwasher and into your home's drainage system.
Tools and Materials Required
Before you begin, gather the following tools and materials:
| Category | Item | Description |
|---|---|---|
| Tools | Adjustable wrench | For tightening fittings |
| Pliers | For gripping and turning | |
| Screwdriver set (Phillips/flathead) | For hose clamps and electrical connections (if applicable) | |
| Utility knife or hose cutter | For trimming drain hose | |
| Bucket and towels | For catching drips and cleaning up spills | |
| Level | To ensure the dishwasher is installed evenly | |
| Materials | Dishwasher supply line | Typically braided stainless steel, 3/8" compression |
| Dishwasher-90 fitting | A special brass fitting to connect the water supply tube to the dishwasher inlet | |
| Teflon tape (PTFE thread sealant) | For sealing threaded connections | |
| Hose clamps | For securing drain hose connections | |
| Garbage disposal inlet connector (if applicable) | For connecting drain hose to disposal | |
| Air gap kit (if required by code) | For preventing backflow into the dishwasher |
Step-by-Step Plumbing Guide
Follow these steps to properly plumb your dishwasher:
1. Preparation and Safety
- Turn off Power and Water: Before starting any work, shut off the power to the dishwasher at the circuit breaker and turn off the hot water supply valve located under your sink. If there isn't a dedicated shut-off, turn off the main household water supply.
- Clear the Area: Remove any items from under the sink cabinet to give yourself ample space to work.
- Position the Dishwasher: Carefully slide the dishwasher into its intended opening, leaving enough room to access the back connections.
2. Connecting the Water Supply Line
The water supply connection is crucial for the dishwasher's cleaning performance.
- Attach the Dishwasher-90 Fitting: Locate the water inlet valve at the bottom front or side of the dishwasher. Apply a few wraps of Teflon tape to the threads of the dishwasher-90 brass fitting. Thread the dishwasher-90 fitting onto the dishwasher's water inlet valve and tighten it securely with an adjustable wrench. This special brass fitting is essential for making the connection.
- Connect the Supply Line to the Dishwasher: Attach one end of the new braided stainless steel supply line to the dishwasher-90 fitting. Hand-tighten, then give it an additional quarter to half turn with a wrench.
- Connect the Supply Line to the Hot Water Shut-off: Route the other end of the supply line to the hot water shut-off valve under your sink. Attach the compression fitting to the valve and tighten it securely. Ensure all connections are snug but do not overtighten, as this can strip threads or damage components.
3. Installing the Drain Line
Proper drainage prevents standing water and ensures hygienic operation.
- Route the Drain Hose: Guide the corrugated drain hose from the dishwasher through the cabinet opening to the sink area.
- Choose Your Drain Connection Method: There are two common methods for connecting the drain line:
- To a Garbage Disposal:
- Locate the dishwasher inlet port on your garbage disposal (often covered by a knockout plug). If it's still plugged, use a hammer and screwdriver or a punch to knock out the plug from inside the disposal, then remove it.
- Slide a hose clamp over the end of the dishwasher drain hose.
- Push the drain hose firmly onto the disposal's inlet port and secure it with the hose clamp.
- To a Sink Drain (via Tailpiece):
- Your sink drain's tailpiece (the vertical pipe directly under the sink strainer) may have a dedicated barb fitting for a dishwasher drain hose.
- If not, you may need to install a special tailpiece with a dishwasher barb.
- Attach the drain hose to the barb fitting with a hose clamp.
- Using an Air Gap (if required by local codes):
- An air gap is a device installed on the countertop next to the faucet, preventing contaminated water from flowing back into the dishwasher.
- The dishwasher drain hose first connects to one side of the air gap.
- A second hose then runs from the other side of the air gap to the garbage disposal or sink drain.
- Secure all connections with hose clamps.
- To a Garbage Disposal:
- Create a High Loop (if no air gap): If your local codes do not require an air gap, create a "high loop" with the drain hose. This means securing the drain hose as high as possible under the sink counter before it connects to the disposal or sink drain. This prevents dirty water from flowing back into the dishwasher and helps with proper draining by creating an air break. Use a strap or clamp to secure the loop.
4. Final Checks and Testing
- Inspect All Connections: Double-check all water supply and drain line connections to ensure they are tight and secure.
- Restore Water Supply: Slowly turn the hot water supply back on at the shut-off valve. Check carefully for any leaks at the supply line connections.
- Restore Power: Turn the power back on at the circuit breaker.
- Run a Test Cycle: Run a short rinse cycle or a complete wash cycle without dishes. Monitor the connections under the sink closely for any leaks. Pay attention to both the water supply and drain lines. Listen for unusual noises during the drain cycle.
- Adjust and Level: If any leaks are detected, shut off the water immediately and re-tighten the connection. Ensure the dishwasher is level using a spirit level and adjust its feet if necessary.
Properly plumbing your dishwasher ensures its longevity and efficient operation, providing sparkling clean dishes with every wash. If you encounter any difficulties or are unsure about local plumbing codes, consider consulting a qualified plumber.
