[LazyPup]

Anyone who has ever dropped a washing machine hose while the tub was full knows only too well that there are no valves in the washing machine drain line, instead the water is kept in the tub by keeping the drain line elevated to a point higher than the top of the tub. In this manner even though the the water in the drain line will always seek the same level as the water in the tub the water is contained until such time as the pump pushes it over the top. (See Illustration).

If a drain line were to be elevated above the tub then run down and tightly connected to the drain line we have another problem. As the water is now pumped out of the tub the level of water in the tub will eventually be below the level of the water in the high loop of the drain line. In this configuration when the pump stops the water on the washer side of the high loop would then fall back to the washer by gravity. This action would create a syphon effect and would result in sucking effluent from the drain line back into the washing machine. This would then present a serious health risk to whoever uses the washing machine or wears clothing that had been processed in this washer.

Contary to public opinion the Plumbing Code is not a building code but rather it is a very elaborate health code designed to insure there can be no cross connection between the sanitary waste and potable water systems or to prevent any personal exposure to contaminated sanitary waste. With this in mind, the code requires that a washing machine, dishwasher or water treatment sytem drain line MUST BE connected to the house drainage system by means of an approved "Indirect waste". By extension, when it is necessary to connect an Air Conditioner or Dehumidifier condensate drain line to the house drainage system they must also be connected by means of an indirect waste receptor.

By definition an "Indirect Waste" provides an air gap between the discharge line and the house drains.

As you can see in the attached illustration a when a washing machine drain line is connected to a standpipe the top of the standpipe is also open to air, therefore when the pumping action stops air can enter into the line to prevent the possibility of water from the drain being syphoned back into the washer.

An alternative method of creating an indirect waste for a washing machine is to simply discharge into a laundry sink which provides about a 10 or 12" vertical air gap from the output end of the washing machine line to the input of the sink drain.

While obviously not practical for a washing machine, a floor drain can also be used as an indirect waste receptor for an AC or Dehumidifier discharge line. When doing so the output end of the discharge line MUST BE affixed in such a manner as to insure a minimum of 2x the line diameter or a minimum of 2" , whichever is greater, above the drain opening.

When installing a dishwasher we have three common alternatives. 1. The Dishwasher input port on a garbage disposal, 2. an approved "Air Gap" fitting installed above the counter top or 3. when the dishwasher is remote from the sink area we may install a standpipe under the counter in the same manner as the laundry standpipe. (Some local codes require an approved air gap fitting on all DW installations).

Now in regard to your question about using a pump. Here we have two options. You could use a small utility pump to lift the water from a sink up to the drain pipe but it would also be required to be connected by means of an approved indirect waste. (a standpipe).

The alternative would be to install a "Sewage Ejector Pump" system.

Due to the complexities involved in engineering and installing a sewage ejector pump I will prepare a separte posting on that topic.