How to drain and flush a Bosch water heater: A step-by-step guide

If you want to work on a water heater that has a tank, it is a great idea to drain it. This water is very heavy and can be quite hot so you have to be careful when you do this.

 A lot of manufacturers recommend that you do this every year to remove the sediment from the tank. This prolongs the lifetime of your tank.  In this article, we will discuss the best approach to drain a water heater. 

Preparation and tools that are needed

It is best to wear boots and gloves for this. Wearing safety goggles is a great idea as well. It is always possible that air or water can escape and it is best to be prepared for this. You will also need a hose to drain the tank. A normal garden hose can’t be used as this often can’t withstand hotter temperatures.

You will need a 5-gallon bucket, a wrench, and a flathead screwdriver.

Unplug the Bosch water heater 

There is an electrical wire connected to the recirculation pump. You unplug this and this will stop the pump. It is a good idea to do this when the pump is not working. This makes sure that the pump doesn’t block in the middle of a cycle.

If you have a water heater that works on electricity, you can unplug this as well. 

If your water heater uses gas, you can close the valve. Make sure that you don’t smell any gas before proceeding. Close the valve gradually. You might have to use a wrench if the valve hasn’t been used in a while. Be careful when you do this as valves are not that strong. You might have to replace it if it doesn’t work that well anymore. 

The water in the tank can be quite hot so it could be a great idea to wait a few hours to proceed.

Close the water valve

On the cold water side, there is a valve. We are going to close this so that no new water is added to the tank. If we don’t close this, the water will keep running even when the tank is already empty. You might have to close the main water line if your tank doesn’t have one.

Connect the hose to the drain valve.

This is often a copper piece at the bottom of the tank. You simply attach a hose to it with a metal connector. You can use a wrench to make sure that the hose is firmly in place. Place the end in a big bucket.

Now it is time to open the drain valve. Sometimes you will need a flathead screwdriver to do this. In other instances, there is a handle that you can turn. 

Let air in the tank

Air will push the water out of the tank. You can open up the pressure release valve on top of the tank. This is often a spring-loaded valve so easy to open. 

 If you don’t have this on your tank, you will have to use a wrench to open up a nut on top of the water tank. This removes the cold water supply from your tank (remember that we closed this before) and will allow air to enter the tank.  Be careful when you do this so that you don’t damage other parts of the tank. 

Let the tank drain completely. This can take some time so be patient. The water can be hot so be careful when you do this.  Check the color and sediment in the bucket to make sure that nothing is wrong with your tank. If the color is brown or dirty, it can be a great idea to run a camera in your system to see if something is going wrong or not. 

Flush the Bosch water tank

We are going to clean the tank by opening the cold water supply. Reconnect the nut before doing this if you had to remove it to add air to the tank. Place the hose outside or on a drain inlet. The bucket might not be able to handle all this water as it has to run for 5 minutes. 

Water will flow through your tank and remove any sediment that is still present. This properly cleans your tank. 

Close the drain valve and disconnect the hose

Now that the tank is cleaned, we can use our screwdriver to close the drain valve on the tank again. We can remove the hose. There might be water in it so be careful. Once this is done, we can discard the water in the bucket. We can also close the pressure release valve. 

If you didn’t flush the tank, you can open the cold water supply. Check that there are no leaks before proceeding. 

Restart the heater and pump

This is generally done by plugging the tank and pump in. Check the manual of your Bosch device to check if something special is needed. Newer tanks have a digital display to indicate what steps need to be taken. If you have a tank that works on natural gas, you have to open up the gas valve as well. 

 It can be a great moment to tweak some settings on your tank as well. For example, lowering the required temperatures somewhat can lead to savings. A lot of people just use the factory settings but these might not be ideal for your situation.

To conclude, we can state that it is generally is quite easy to drain and flush a water tank. This often needs to happen every year. Check the instructions of your system to see if something different needs to happen. 

This is a great moment to check for leaks and to optimize your system. It is a great idea to do this every fall so that your system is ready for winter. If there is a problem, there is still time to call a plumber. Plumbers are often very busy during the winter and they might charge more if you have a problem at that point in time. 

Double check the manual of your heater as each model is different. 

Bosch is a German brand that has a rich tradition. They are making premium devices and they often back this by offering an extended warranty. Their water heaters generally last 10-15 years if they are well maintained. Flushing a water heater is part of this process.

If you have problems with your Bosch water heater, you can reach them on the following phone number: Phone: (917) 421-7209. They can assist you with any problems that you have. Bpsch water heaters have a lot of sensors and these can guide you as well.

If a light is flickering, you can generally find the cause of the problem in the manual or online.

https://www.bosch-thermotechnology.us/us/en/residential/service/documents-media/downloads-for-bosch-products/manuals/gas-tankless-water-heater-manuals/