Start with filled weight
One litre of water weighs about one kilogram before the can itself is counted. 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
A long spout reaches beneath foliage and places water close to the compost surface. A fine rose breaks the flow into gentle droplets for seed trays and newly sown beds; established containers can accept a faster flow if it does not scour the mix. 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. Metal cans are durable and repairable but may corrode; plastic cans are light and corrosion-resistant but 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 a separate, clearly labelled can for feeds or other garden treatments, and never use a food or drink container for mixed products. Follow each product label for application, cleaning and disposal.