As a standard immersion heater is 3KW, so it would take 2 hours to heat 100 Litres of water. After an hour and a half, it will only have reached about 53 degrees.....
Podiatrists cite Plantar Fasciitis as being the most common cause of heel pain. Typical symptoms of this condition include sensations of pain, burning or heat in one or both heels.
Plantar fasciitis. Plantar fasciitis causes pain in the heel and bottom of the foot. It is due to inflammation of the plantar fascia. The plantar fascia is a muscle-like connective tissue at the bottom of the foot. Plantar fasciitis is associated with overuse, such as with runners, or in cases of obesity.