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 (say PLAN-ter fash-ee-EYE-tus) is the most common cause of heel pain. The plantar fascia is the flat band of tissue (ligament) that connects your heel bone to your toes. It supports the arch of your foot. If you strain your plantar fascia, it gets weak, swollen, and irritated (inflamed). Then your heel or the bottom of your foot hurts when you stand or walk. Plantar fasciitis is common in middle-aged people. It also occurs in younger people who are on their feet a lot, like athletes or soldiers. It can happen in one foot or both feet.