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What is the maximum length for a washing machine drain hose?
Friday, June 15, 2018
The answer to this question is complicated by the fact that it is much harder to pump water vertically than horizontally. Washing machine manuals typically specify a minimum height of 39” for the entry of the drain hose into the standpipe or faucet box, and a maximum height of 96” (8 feet). The minimum height is intended to avoid backflow siphoning of the drain water into the machine, and the max is the tallest column of water that the drain pump is rated to handle. But no horizontal dimension is specified. Here’s the specs in a Whirlpool manual, shown below.
When we called Whirlpool customer service, their recommendation was don’t add more than a 4-foot extension to the basic drain hose, which would allow placement of the washer about five feet from the termination. We recently encountered a washing machine that had been relocated from one side of a long laundry room to the other, with a series of drain hose extensions that ran about 12 feet along the floor at the baseboard, then up to the standpipe.
There was a noticeable foul smell in the empty washing machine, however, which was due to the standing water in the hose along the floor that remains after the washer tub has been pumped out. Washing machine drain water contains organic debris from food stains and shed skin cells, along with trace fecal matter from underwear. It accumulates a crust on the long section of hose along the floor, which is what a plumber would call a “trap,” similar to the small reservoir of water in the U-shape under sinks that keeps sewer gas from rising up through the drain—but exponentially larger.
It’s a stinky problem that can be solved by elevating the hose behind the machine to a height above the level of the distant standpipe or faucet box where it will terminate, and creating a slight downhill slope in the long horizontal run of the hose so it will drain by gravity after the pump stops. But that means that the hose will be exposed on the wall and have to be well supported along the run to prevent sagging, or a PVC pipe can also be used as an alternative. Both solutions are practical, but not especially attractive. Keeping the washing machine as close as possible to the drain connection is always the best solution.
Also, see our blog posts What is the correct height for the washing machine drain standpipe or outlet box? and Is a washing machine drain hose required to be secured at the standpipe? and Why are rubber washing machine hoses a safety risk? and What are the most common problems with washing machine installation and maintenance?
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