Start with filled weight
One litre of water weighs about one kilogram before the can itself is counted: 5 litres adds about 5 kg and 10 litres adds about 10 kg, plus the weight of the empty can. A large can reduces trips but can be awkward to lift, carry and tip accurately. Choose a volume that every intended user can manage when full, or fill a larger can only part way.
Two handles allow the load to be shared during carrying and pouring. Test whether the can remains balanced as the water level falls and whether there is enough clearance around the top handle for a gloved hand.
Match the spout and rose to the job
Match the task to the feature: seed trays and newly sown beds need a fine rose and gentle, even flow; established containers need controlled flow that does not scour the compost, though a faster flow may be suitable; watering beneath foliage calls for a long spout to reach the compost surface. A removable rose is easier to clean and lets the can deliver directly when appropriate.
Check that the rose fits securely in its intended orientation and does not leak around the connection. Material trade-offs vary between products: metal cans can offer durability and may be repairable, but can corrode; plastic cans can offer light weight and corrosion resistance, but may become brittle with age and sunlight.
Water the root zone, then check it
Apply water slowly enough to soak in instead of running across the surface or out of a dry gap at the edge of a pot. Water around the established root zone rather than wetting only the stem. Seed trays need a gentle, even pass so seed and compost are not displaced.
Do not judge success by the surface alone. Check moisture at a useful depth with a finger, trowel or other appropriate method, and adjust for weather, plant size, soil and container volume. A garden watering plan can help group areas with similar needs.
Prevent blockages and contamination
Empty the can after use and rinse out sediment. Remove the rose and clear blocked holes without enlarging them. Store plastic out of strong sunlight and protect metal cans from persistent moisture and frost damage.
Keep clearly labelled equipment for feeds or other garden treatments separate from the plain-water can. Do not assume one treatment can is suitable for all products: follow each product label for suitable equipment, application, cleaning, reuse and disposal. Never use a food or drink container for mixed products.