220V grid,16A breaker looks like a continental Europe.
I use exactly the same setup with washing machine and dryer plugged in a single 16A socket protected by the same 16A breaker for quite a while (~10 years). No single breaker trip, ever.
The reason why this works:
- the washing machine and the dryer are usually used sequentally - you have to wash something in order to dry it afterwards.
- neither the washing machine nor the dryer run always at their rated power.
The washing machine uses the heater element (the most power-hungry part) for a few minutes after the start and then cuts it off. Only the motor and the valves are used afterwards, the motor consumes few tens of watts when rotates the drum during the washing cycle and 200-400W when spins.
The dryer also heats up the air inside for less than a minute and then cuts the heater off, switching it on only for a short periods to maintain the temperature. If the dryer is heatpump-based, the rated power is consumed only for 1-2s when the compressor starts, then it draws like 400-500W and is also interrupted periodically.
- The breaker, as well as the wires and the socket, have some tolerance for temporary overloads.
Yes, the breaker is expected to protect everything else from overload, but a 16A breaker will allow for 1-2 minutes 20A load. In your setup, this never happens even if you time the both machines to turn on their heaters together.
A plug that measures the consumed power is a useful device - especially if you like to know where the electricity bill goes. Most of them have a memory for a maximum load, show the instant measure as well as accumulating function (just like the electricity meter used by the utility company).
A water heater on the same circuit is a big NO. (but see below)
Water heaters are usually 2000-3000W (9-13A, volume or tank heaters) or 6000-10000kW (25-40A, instant or tankless heaters).
What's more, a volume water heater usually draws its rated power for prolonged periods (hours) so you cannot really expect it not to coincide with other appliances drawing power.
The only way a water heater can safely coexist with some other appliance is time separation - say, water heater has power-on timer. It turns on only between 04:00 and 06:00 early in the morning when no one would use neither the washing machine nor the dryer. (Yes, I did use this setup for a while with no ill effects other than not having hot water for more than two showers)