Fixing Water Dispenser Which Dispenses Hot Water From Both Normal and Hot Tap



Water Dispenser Parts Description of the parts:
A = normal water tank
B = normal water tap
C = one way valve
D = boiling water tank
E = hot water tap
F = overflow / hot vapour escape
G = drain hole
H = heating element
J = thermostat


Normally a hot water dispenser works like this:

  • Normal water flow: A > B
    The normal water from your water bottle will flow from normal water tank (A) to normal water tap (B) when you open tap B.
  • Hot water flow: A > C > D > E
    When you open hot water tap (E), the water from tank A will flow through a one way valve (C) to boiling water tank (D). The water will then be boiled by the heating element (H) and the temperature will be controlled by a thermostat (J). The hot water will flow upward, enter the hose to hot water tap (E). That is why the water entrance hole to the boiling tank and the heating element (H) both are placed on the lower side of the tank, while the thermostat (J) and hot water hose are placed on the upper side. There are 2 effects of boiling water: increased preasure and hot vapour. These effects must be anticipated by connecting the topmost part of the hot tank and the topmost part of the normal tank through hose F. This hose F will help the overflow and hot vapour escape from the boiling tank. This hose F is usually smaller than other hoses, to increase the efficiency of the boiling water time. There is also an important one way valve (C) which ensures that the hot water from the boiling tank does not flow upward and mix with the normal water (D > C > A).

If both your water taps dispense hot water, there are 2 suspects and the solutions:

  1. The thermostat (J)
    A thermostat controls when the heating element starts and stops boiling the water. When a pre-defined boiling temperature is reached, the thermostat (J) will stop the electric current to the heating element (H), by increasing the internal resistance (ohm). But if the thermostat is broken, it will fail to detect the temperature and make the heating element keeps boiling the water although the boiling point has been reached. This condition increases the hot vapour volume and makes the boiling water pushed upward and flow through the overflow escape (F) then mixed with the normal water in tank A. This causes the normal water tap (B) also dispenses hot water from tank A.
    Solution:
    Replace the thermostat by unscrewing its fasteners. Take the sample to your local electronic component store and buy a new one. Make sure the temperature code marked on the new thermostat matches yours (A difference of 1 or 2 degrees is still okay). Also make sure the head size and screw hole spacing match yours for ease of installation.

  2. The one way valve (C)
    This valve makes sure the water always flow from upper normal tank (A) to lower boiling tank (D) in one way direction. This prevents hot water from the boiling tank goes upward and mixes with the normal water. If this happens, your normal water tap (B) will also dispense hot water.
    Solution:
    Remove the one way valve (C) from the hose and clean the inner part of the valve with water, soap and a toothpick. Shake it vigorously and rinse it thoroughly with water. Check the result by blowing the valve as you blow a whistle. A good one way valve will stop the air flow from one direction but allow the air flow from the other direction. By blowing the valve you can check if your blowed air can go through the valve or not. If the one way valve is normal, reinstall the valve to the hose. PLEASE DO NOT install the one way valve in a wrong direction, always blow both sides of the valve to determine in which way the valve should be installed. Mark an arrow on the outside of the valve with a pen if necessary. A wrong reverse installation will make the water never reaches the boiling tank.

How to identify whether the problem is on the thermostat (J) or the one way valve (C)

Open the normal water tank (A) cap, there you will see 2 big holes on the bottom of the tank connected to tap B and tank D, and 1 (or 2) small hole on the upper part of the tank from hose F. Fill normal water tank (A) until it reaches the maximum level. Wait until the water flows to other hoses/tanks and refill it again until maximum level. After the water in tank (A) stops decreasing and all hoses/tanks are full of water, drain tank A by opening tap B (normal water tap) only. Once it is drained, turn on the water dispenser and make sure it starts boiling the water by checking the boiling indicator (usually red light). Wait for some times after the boiling indicator has stopped or after quite a long time (20 minutes or more), then observe both the big and small holes inside tank A. If the big hole connected to the boiling water tank through hose C, spouts hot water, the problem is on the one way valve. But if the hot water is spouted from the small hole connected to the boiling tank through hose F, the problem is on the thermostat. If the boiling red indicator never goes off forever, it also indicates a problem with the thermostat.

I hope this article will help you solve the problem with your hot water dispenser which dispenses hot water from both normal and hot water tap. Good luck.



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