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Can a dishwasher drain hose be connected after the sink trap (to the trap arm)?
Saturday, October 5, 2019
No, the dishwasher discharge must be connected before the trap. According to the Florida Plumbing Code it must "discharge into a wye branch fitting on the tailpiece of the kitchen sink or the dishwasher connection of a food waste disposer.” The International Plumbing Code citation is similar.
There is also an alternate method allowed, of an indirect drain with an air gap, which we have never seen at a built-in dishwasher installation. So the example shown below, where the discharge line is connected after the trap at the trap arm, is not allowed.
The reason that connecting the discharge after the sink trap is prohibited is that this wrong configuration is behind the U-shaped plug of water that keeps stinky, and sometimes lethal, sewer gases collecting in the dishwasher.
And here are two examples of the correct way to do it.
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Here’s links to a collection of some of our other blog posts about APPLIANCES:
• What are the building code requirements for installing an appliance (furnace, air handler, water heater) in the attic?
• Which house appliances need a dedicated electrical circuit?
• Is a washing machine drain hose required to be secured at the standpipe?
• When was GFCI-protection for kitchen dishwasher receptacle outlet first required?
• Why does venting a clothes dryer into a garage, attic, or crawl space cause problems?
• Does a refrigerator water supply line require a shutoff valve behind it?
• My spa tub stopped working. What's wrong?
• What is the maximum recommended height above the floor for an above-the-range microwave?
• Why would a home have natural gas appliaces but no gas meter?
• Is a hot water faucet required at a washing machine?
• Can I remove a 240-volt range receptacle and hard-wire the range?
• Can a dishwasher be wired to a kitchen counter small appliance receptacle circuit?
• Why is it bad to have a clothes dryer vent near an air conditioning condenser (outdoor unit)?
• Do home inspectors test the appliances?
• What are the most common defects with over-the-range microwaves?
• Are a range and refrigerator required kitchen appliances for a house to pass FHA inspection?
• What are the code requirements for an outdoor dryer vent cover?
• What is the maximum length for a clothes dryer vent?
• Why are my ceiling fan blades drooping?
• How do you inspect a dryer vent?
• Why is there a water hose connected to the back of the clothes dryer?
Visit our APPLIANCES and PLUMBING pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.
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