Tap water is obviously the first choice for simplicity, but it is not always the best. First, when you need water most, during a drought, they put a ban on using it! Also, municipal water is supplied under pressure and this can sometimes be too great for automatic irrigation systems, which may need a separate self-filling header tank (a toilet cistern will do). Pressure can vary by the hour in some areas¡ªif you suffer from low pressure, try to water before everyone else gets up and see if this makes a difference. All water supplies to a garden need to be fitted with a non-return valve to prevent contaminated water from being pushed back down the pipe. Large gardens may need their own separate water supply, especially if you have to fill a pool of any size. You may want to install computer-controlled automatic sprinklers, but make sure your water supply is large enough to cope to avoid having to upgrade it part way through.
Although tap water is sterile and safe, it is often very chilly and can be full of chlorine. This may not pose a problem when it is sprayed or irrigated on hardy outdoor plants, but it can shock tender and greenhouse specimens and therefore should be allowed to warm up before application. If space allows, consider fitting a holding tank in the greenhouse, where the water can give off some of the chlorine; this can also be an opportunity to add some liquid feed to the water.
Hoses and faucets
A proper faucet and fitting make sense. If your garden is large, or if you have a greenhouse, you may need more than one. For spraying and watering plants, a rubber or plastic hose will be necessary. Choose the best quality you can afford¡ªthe better ones kink less and last longer. A reel mounted on a wall is probably the best place to store a hose when not in use. It is also worth investing in quick-release junctions, sprinklers, and so on if you expect to water often.
When water freezes, it expands and this can cause pipes and hoses to break or crack. For this reason, all pipes must be well insulated. In very cold spells, it is also worth draining down watering systems for extra safety. Empty rubber and plastic-hoses and store them in a frost-free shed. If they are accidentally left out in freezing weather, avoid moving them until after the water has thawed and warmed up to prevent them splitting, be careful of dripping pipes, which can freeze drop by drop until the pipe blocks and the water backs up.
Wills, pools, ponds, and ditches
To supplement your water supply, you may also wish to take water from wells, pools or ponds. This is usually warmer than tap water and free of chlorine, but it may be muddy or carry disease. If you have your own well, and it is fairly deep, it should contain fairly cold, cleanish water; however, if it is a shallow, ground-water sump-type well the water may be dirtier. In either case, make sure you stand the water in a settling tank to warm up before giving it to tender or greenhouse plants. Water from pools, ponds, and ditches is usually warmer, and even muddier. Such dirty water may be full of plant nutrients, diseases, or even pollution, so make sure you use it with care. Simple electric pumps enable all these sources of water to be utilized.