In addition to the high risk of blowing up washing machine pumps (see Laundry to Landscape), with simple hoses such as these, the following were particular problems in Australia:
Over watering / Under watering
With simple hoses, all the water (often 40 gallons per wash) is dumped in one small area of the garden, resulting in over watering that area, with other areas going dry. Similar to bucket watering, people would concentrate water in their favorite areas, in the end killing with over watering.
Due to high soil pH, micronutrients are bound to the soil and become unavailable to plants. Chlorosis is most commonly caused by iron, but can also be caused by manganese and zinc deficiency. Commonly affected plants are pin oak, sweet gum, white oak, and rhododendron.
The most prominent symptom of iron chlorosis is leaf yellowing. The veins of the leaves stay green, while the rest of the leaves turn yellow.
The issue is primarily the first load of water from the washing machine. Virtually all effective washing powders, ‘eco-friendly’ or not, need high pH water to wash the dirt from the clothes. The pH of this first amount of water is 10.5. As the washer processes each cycle, the pH of the water in drops.
If you were to temporarily store all of the water from one wash, the overall pH is generally between 8.5 and 9.5 which is ok for most gardens.
Always watering in one area with pH 10.5 water will kill plants. If you are going to move a hose around, move in a different pattern each day.
These diverters come in many shapes and styles. They divert water from showers (pipe under the house) and laundry (often a vertical pipe on the outside wall). Gravity hoses can then be connected to the diverter valve.
Although shower water is basically pH neutral, and therefore removes pH risk, over watering becomes a significant issue, especially when diverting all shower water, and not moving the hose each day.
Over watering remains a significant risk for laundry pipe diverter and hose sets. A more sophisticated diversion system is the Branched Drain Network.