This type of cylinder is recommended if you have 2-4 bathrooms as water is at mains pressure, the advantage of this type of cylinder are you can run 1-3 showers without pressure loss (as long as you have good mains pressure) with the advantage of plenty of stored hot water. The disadvantage as stated above is poor mains pressure (poor hot water) also note if cold mains ever gets turned off in the street you will have no hot water.