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.
Heel pain. The most common cause of heel pain is plantar fasciitis, inflammation where this long ligament attaches to the heel bone. The pain may be sharpest when you first wake up and put pressure on the foot. Arthritis, excessive exercise and poorly fitting shoes also can cause heel pain, as can tendonitis. Less common causes include a bone spur on the bottom of the heel, a bone infection, tumour or fracture.