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.
Conditions that may cause heel pain include: 1  When the tendon that connects the back of your leg to your heel becomes swollen and painful near the bottom of the foot. 2  Swelling of the fluid-filled sac (bursa) at the back of the heel bone under the Achilles tendon (bursitis)  Bone spurs in the heel.