Winterize Bosch Electric Water Heater

If you live or travel in cold climates in a van or RV, winterizing your water system is crucial. Last year, I assumed that running my pump would be enough to drain my Bosch electric water heater. Spoiler: it wasn’t. When spring arrived, I refilled my van’s water system, turned the pump on, and the heater instantly exploded, flooding the van. Lesson learned.

This year I'm spending a few months in Colorado, so I decided to follow proper winterizing steps. My Bosch heater is hard-piped with rigid lines, making it impossible to remove or flip.

Below is the exact method I used to drain and winterize a Bosch 5 gallon electric water heater without removing it. I couldn't find any good guides on this so I created my own!

I’m not a professional. This is simply how I successfully drained my system. Perform these steps at your own risk.

* Disclaimer: This page contains various affiliate links that provide a small kickback to me, at no additional cost to you.

‍Tools & Supplies You’ll Need

Screwdriver (flat + philips)
Socket wrench
Towels
Aluminum foil (to create a small gutter)
Small flexible hose (for siphoning)
Optional: new gasket or heating element if yours is worn or mineral-covered

Before You Start: Safety First

Turn off power to the water heater.
I turned off the inverter AND turned the fuse off.
Make sure the water in the water is not hot
Shut off your water pump
Shut the water supply valves to the water heater

How to Drain a Bosch Electric Water Heater (Without Removing It)

1. Remove the Access Plates

Pop out the plastic plate using a flathead screwdriver.
Unscrew and remove the inner plastic cover to expose the metal plate and gasket.

Instructions from maintenance manual here

2. Create a Drain Gutter

Because the opening is awkward and the water flow unpredictable, I created a small gutter using shaped aluminum foil.

It’s cheap
Easy to mold into place
Protects the surrounding area from flooding

Place towels underneath the unit—water will start to appear as soon as you loosen screws in the next step.

Position the foil gutter on top of towels and so it directs water out of the van.

3. Loosen the Metal Plate Bolts

The metal plate is held in place with four bolts. Behind it is the water tank itself.

Loosen each bolt slowly and evenly.
As soon as the gasket starts to break seal, water will begin to flow.
Stop when you get a steady flow and let it drain through your foil gutter.

Let the water drain fully until the flow slows to a trickle.

4. Remove the Plate & Gasket Completely

Once the flow has slowed:

Remove all four bolts.
Pull off the metal plate and rubber gasket.
You now have direct access to the interior of the tank.

5. Siphon Out Remaining Water

There will still be water sitting at the bottom. Use a small, flexible hose to siphon the remaining water into your container. Since I didn't take out the heating element it took some faffing around to actually get the hose in the right position to drain the water. Had to do it a few times before it looked like the tank was fully empty.

6. Inspect the Heating Element

While everything is open:

Check for mineral buildup
Clean if needed
Replace the element if it’s heavily scaled

Bosch recommends inspection during maintenance, so this is a convenient time to do it.

As you can see mine is pretty gross, but I didn't replace it because I didn't have the time.

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Ta-da! That should be it. While admittedly I haven't tested this AFTER winter yet, I have high confidence (and even higher hopes) that I won't flood my van again and need to replace my heater in the spring.

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