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.
Your doctor will examine your heel, looking and feeling for signs of tenderness and swelling. You may be asked to walk, stand on one foot or do other physical tests that help your doctor pinpoint the cause of your sore heel. Conditions that cause heel pain generally fall into two main categories: pain beneath the heel and pain behind the heel. Pain Beneath the Heel If it hurts under your heel, you may have one or more conditions that inflame the tissues on the bottom of your foot: 1  Stone bruise: When you step on a hard object such as a rock or stone, you can bruise the fat pad on the underside of your heel. It may or may not look discolored. The pain goes away gradually with rest.