I just moved into an older house and there is only a cold tap for the washing machine. The machine is located right next to the boiler so I was wondering if I could just attach the hot water hose to the drain outlet located at the bottom of the boiler to give the washer hot water. I checked and the hose attaches just fine.

Any help would be really appreciated!

  • Are you sure your washing machine can accept hot water? Unless it has 2 inlets, feeding it with hot water only messes up the programming (eg the program actually depends on the time it takes to heat up the water) so you only get incomplete washing at larger cost.
    – Agent_L
    Sep 14 '16 at 15:02
  • How far away is the hot water heater? If it's also in the basement, it's a pretty simple job to run a branch line over near to the washing machine. Sep 14 '16 at 19:26

Sadly, the answer is "no". Hot water, both in the boiler and in the radiators, is very corrosive IF there is oxygen in it. Water from your well or town has dissolved air, including oxygen (it's why fish survive in water). Once the water is in the system, the oxygen combines with the boiler/radiator linings, corroding it.

There isn't a lot of oxygen in any one volume of water, and the oxygen in the system will soon get used up, stopping the corrosion. However, if you keep changing the system's water (typically through a leak, or with your suggestion wholesale by taking the system water for your washing machine) then you're continually replenishing the water and thus its contained oxygen. Bingo: corrosion city.

There's almost certainly other good reasons as well (e.g. the water in a boiler is fairly low-pressure, so you wouldn't get great water flow; the boiler fill valve isn't meant to run constantly, etc.), but having to replace your boiler and radiators every few years would trump it all.

  • Other chemical properties? I suspect water is largely made up of Oxygen (and Hydrogen) and that the corrosive properties are similar to the chemical balance of pool water... Acid/alkalinity/calcium. Langlier Saturation Index
    – Tyson
    Sep 14 '16 at 23:01
  • @Tyson Perhaps, but I bet you don't keep your pool water at 160°F. Sep 15 '16 at 19:20
  • Also using that boiler drain for your washing machine will most likely cause damage to the boiler itself Sep 15 '16 at 19:39
  • @DanielGriscom heating water puts off oxygen as gas, most of which is reabsorbed very quickly as it moves into slightly cooled water leaving the heat exchanger, the residue not reabsorbed being the "air" people bleed out of their lines. I don't see any type of water (H20) lacking oxagen which your answer indicates is depleted over time. I suspect boiler water runs highly alkaline much like pool water tends, I don't know that however, not do I know what boiler owners actively do (if anything) to balance water and make it less corrosive, a factor that's probably greater at 165degress than 85.
    – Tyson
    Sep 16 '16 at 1:08

In the UK, most washing machines are cold fill only for energy efficiency reasons. If you happen to have a machine with hot and cold fill you would usually buy a Y piece to feed the hot and cold inlets from a single cold supply.

[Not strictly an answer but I don't have enough rep to comment.]

  • But why bother? If you don't want hot water, then just connect the cold and select only ColdWash-ColdRinse settings. Sep 14 '16 at 19:27
  • The washer heats the cold water internally more efficiently than the boiler that supplies hot water to the taps in the house. So you still get all the wash options even though you're only using the cold supply.
    – Carl
    Sep 14 '16 at 20:47
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    @CarlWitthoft most washers will not work properly if they are designed to use a hot and cold connection. I'm not exactly sure what would happen (since I'm not crazy enough to try), but you would most likely end up with a flood unless the inlet isn't capped. You may also end up burning up the pump (if present) from running it dry. In that case, it is usually better to supply both with cold water. Sep 15 '16 at 19:36
  • 1
    @JasonHutchinson Exactly. If you select a "warm" position it's going to open both hot and cold valves, putting both inlets in communication causing cold water to gush out the hot inlet. Sep 16 '16 at 16:43

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