How to Dissolve Lime in Hot Water Heater

If you have a water heater in your home, one of the things you need to do is to descale it from time to time. When you heat water, it leaves dissolved salts (TDS) or lime on the unit which continuous to build up with time.  Lime contains carbonates, calcium, hydroxides and oxides. This build up is very dangerous because it can cause the heater to overheat. Apart from that, it affects the efficiency and the flow of the water heater. In this article, we shall guide you on how you can de-lime a water heater.

How to Dissolve Lime in Storage Water Heater

De-lime a Water Heater Requirements

  • 3-4 gallons of apple cider vinegar
  • Garden hose
  • Adjustable wrench
  • Toothbrush
  • ¾ inch Allen wrench


  1. The first thing you should do is to turn off the water heater breaker. Place a piece of tape on the breaker and ensure that no one turns it on when you are working. Switch off the pilot light in case you are using a gas water heater. Use the adjustable wrench to disconnect the water supply to the heater.
  2. Turn a hot water faucet on at half strength to vent the heater. Allow the faucet to run for some time. Using an adjustable wrench, open the drain valve located at the bottom of the heater until you see some drops of water trickling out of the valve.
  3. Connect the garden hose to the drain valve and tighten it using your hands. The other end of the garden hose should be placed in a bathtub or a sink. Slant the hose downward to allow the water to drain properly. You should also ensure that there are no kinks on the hose. Wait until all the water has been drained completely. This should take roughly 30 minutes if you are using a 40-gallon tank. Turn off the hot water faucet when the tank is empty.
  4. Look for the anode rod or a large, recessed bolt at the top of the water heater tank. Most anode rod are secured by a hex head screw which means that you need an Allen wrench when removing the screw. Remove the anode rod completely from the water.
  5. Put 3-4 gallons of apple cider vinegar in the hot water heater and allow the vinegar to remain in the heater for at least 24 hours. Unlike the white vinegar, apple cider vinegar contains an acidic value which is able to dissolve lime.
  6. Open the drain valve and allow the vinegar solution to drain. Check the hose from time to time for large chunks of lime. After draining the tank, you should wipe the anode rod using apple cider vinegar and then re-insert. Check whether there are any leftovers of lime deposits on the drain valve. Remove any remains using a toothbrush. After you have removed all the lime, you can now close the drain valve.
  7. Turn on the hot water faucet to vent the system. You can also turn the water supply back and then allow the tank to fill until the water starts to enter the tank. When this happens, shut off the hot water faucet. Before you turn on the water tank breaker, ensure that the tank is completely full.

How to Dissolve Lime in a tankless water heater

Instant Water Heater

If you suspect that there is buildup of lime in your instant water heater, you should not hesitate to clean it to boost the efficiency and reliability of the unit. Some of the things you will require to do this are;

  • Bucket for collecting the water
  • Washing machine hoses
  • Pump for cleaning
  • Channel lock wrench
  • Descaling solution or vinegar


  • Before you start, ensure the temperatures are at 150°F then allow hot water to run through the unit for one minute.
  • Disconnect the water heater power and then isolate the unit by closing the inlet and outlet isolation valves. In case you are using a unit that doesn’t have the isolation valves, you should buy and install them.
  • Look for a bucket for collecting the water as it drains.
  • Drain the unit and then connect the hoses to the isolation valves drain ports.
  • Fill an empty water bucket with water and then add a descaling solution.
  • Open the two isolation valves and then turn the circulation pup on.
  • Allow the solution to circulate in the tankless water heater for close to one hour.
  • Drain the descaling solution and then flush clean water after closing valve “B”
  • Open the other valve “A” and connect a hose that leads to the empty bucket.
  • Open the inlet water valve to allow clean water to flow in the unit as it drains into the empty bucket. This will ensure that there is no solution that is left in the heat exchanger.

How to prevent lime build up in a water heater

Water Heater Repair Some of the things you should do to prevent build up of lime in your water heater include;

  1. Flushing – Before doing this, you should switch off electricity or disconnect the gas that powers the unit. After this, you can now open the hot water tap that is close to the water heater. You need to be very careful when draining the water because it is very hot. After flushing the unit, you can now open the drain valve to allow the water to move out of the unit. Once the water heater is empty, you can now close the drain valve and then open the water supply.  Lastly, reconnect you can the gas or switch on electricity if you are using an electric water heater.
  2. Setting the right temperatures – Hot water absorbs more calcium. This means that if the temperatures are too high, there will be more calcium deposits on the unit. In order to prevent this, you should always ensure that the temperatures are set at 120°
  3. Using vinegar – Buildup of scale in a water heater can also be prevented by adding vinegar into the unit after you have drained the tank. After emptying the water heater, close the drain valve and then pour one gallon of cider vinegar in the unit. Allow the vinegar to sit in the unit for not less than 6 hours. Use cold water to flush the vinegar out of the water heater. Once you have drained the water and the vinegar, you can now reconnect the gas or electricity supply. Close the draining valve of the unit and restore the water supply.

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Whether you have a tankless or a tank water heater in your home, you need to ensure that it is well maintained. Apart from cleaning it, you will also need to remove lime build up on the unit at least once after 2 years This will enhance its performance and the good thing is that it is not a difficult process. After reading this guide, we hope that now you know how to de-lime your water heater.

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