How to get Hot Water in a Van

It takes just 15 minutes of driving for us to have a full tank (16 litres) of hot water in our van! No electricity, gas or additional diesel required, and let me tell you it feels like absolute luxury!

When we first researched our van build Will came across a few professional RV companies in America that used the coolant (glycol) line from the engine to heat their water. Genius! That heat was going to go to waste so why not put it to good use? Simple eh? Well, yes and no! We did a lot of research and below is what we discovered and how we went about installing hot water in our van.

Is it safe?

We planned to get everything connected by a Webasto dealer at the same time they installed our diesel heater. Our tank is part of the Isotemp range, owned by Webasto and designed for marine environments. Whilst these tanks are used a lot in camper vans they’re not officially endorsed for use in vans any more.

From what we can gather concern was raised by a customer in America that the vibrations experienced by a van when being driven could cause the internal heat exchange element to crack, thereby contaminating the water. This meant none of the Webasto dealers we spoke to were prepared to install the tank as it isn’t officially endorsed by Webasto. We never managed to ascertain if this ever actually happened. We concluded vibrations must also be present on a boat, so we decided the pay-off was worth the risk. So far, we have had no issues.

The other problem we came across online was concern over whether it would draw too much heat way from the engine and thereby shorten the life of the engine. Our engine is already under significant strain as we are always on the upper end of the payload. We also drive in snow, grit, onto beaches and up mountains so we definitely put it to the test!

Essentially, there are many reasons our engine might not last as long as a standard Sprinter Van’s might! Again, we decided the pay-off of having on-demand hot water in our van was worth the risk considering how many other stresses could cause our engine to fail prematurely. We have, however, fully insulated all the pipework to mitigate against heat loss. So far our engine runs at the same temperature it always did, so we’re not too worried!

Heating water with electricity

The last few weeks of our van build were pretty hectic! In the end, we were unable to find someone to fit the system for us and ran out of time. We therefore set off on our first winter adventure to Norway (via Austria, Germany, the Netherlands and Denmark!) relying on our fall back plan; electricity. 

We installed our hot water tank early on in our build (behind the kitchen cupboards). This tank critically features both an electric heating element and an internal heat exchange coil that can connect to an engine coolant line. Initially, for our first 6 months we only connected the electric option.

hot water tank installation

Using electricity to heat a tank of water uses a lot of power. We charge our battery as we drive but to heat a tank of water usually takes around 2 hours driving! If you start with a battery not at 100% charge that requires topping up as well it can mean you need to drive for 3-4 hours to generate enough power. This is especially true in winter when there’s not much solar to top up your battery in the background.

We managed like this for 6 months so it can’t have been that bad! Although, we did drive all the way to the top of Norway and back so were driving most days. We also only heated the tank if we wanted to shower, saving showers for when we knew we’d be travelling. Dishes were done using the trusty boiling water in a pan method! Occasionally we got lucky and found somewhere with free/cheap power and always took advantage of on-demand hot water then!

Using engine heat to get hot water in a van

We eventually got round to connecting our coolant line to our hot water system and we’re so pleased we did! It’s so nice to have the luxury of just running the tap to wash your hands with warm water or to do the dishes. And, whilst we don’t shower daily (that would use far too much of our precious fresh water) it’s really good to have the option! 

Installation Process

1. Install Water Tank

  • We opted for a 16lt water tank that’s often installed in boats. It’s an Isotemp Slim Square Tank that enables us to heat water via electricity if we have hook up or using our engine heat.
  • Get your tank as close to your engine as you can to keep your pipe lengths shorter. We put ours behind our kitchen cupboards, just on the other side of the bulkhead.

2. Install Hose

  • Cut into the coolant (glycol) line and use a pipe joiner to connect your new flexible hose that will link to your tank. Run this hose to the tank and then back to the engine.
  • Join it back to the original coolant line where it was cut, allowing it to continue on its loop.

hot water installation

  • The route we took to get the hose to our water tank came close to the Diesel Particulate Filter (DPF), we therefore fitted some aluminium as a heat shield to protect the new pipework from the heat of the DPF.

hot water installation

  • Don’t forget to run a pipe from the dump valve. This automatically releases water from the tank to relieve pressure once the water is hot. We ran ours through to our shower and it discretely drains into our shower tray.

3. Top Up Coolant

  • You now have a much longer coolant line than before so will need to top up your engine coolant to account for this.
  • Run the engine to get rid of any air and then check your coolant level again. Make sure if you need to top up again that you wait for it to cool and de-pressurise.

4. Insulate External Hose

  • We insulated all the hose running to and from our water tank using pipe lagging and foil bubble wrap. This was both to protect the pipe work and ensure minimal heat loss.

5. Insulate Internally

  • Our tank is insulated but still gets warm, and the pipes running into it from the engine are too hot to touch.
  • Insulate the tank and pipes as much as you can for two reasons: Firstly it stops anything near the tank getting too warm (in our case food in the cupboards!); Secondly, the whole systems acts like a radiator giving off heat. Great in the winter but not so good if you’re in 30°c heat in summer and trying to keep your van as cool as possible.

hot water pipe insulation

6. Be Careful!

  • The water gets very hot! The coolant line runs at around 90°c so make sure you temper the water coming out of your tank. It does mean your hot water will last longer though as you’ll be mixing a fair bit of cold with it to make it bearable to use!
  • Top Tip – There are two trip switches for the electric element in this tank. The first trip is a soft reset that resets itself once the temperature drops back to the expected levels. The second is a hard reset requiring you to press a button that’s not easily accessible as you need to remove the front panel of the tank.

    When you drive up a steep hill the engine is hotter than the thermal threshold for the trip and it therefore kicks in as a safety measure. You will need to reset the second trip before you can heat using electricity again. We discovered this after we’d already built our kitchen around the water tank. You may wish to extend this trip switch to make it easier to access and reset.

That’s the basics of our van hot water system and its installation. If you have any questions or want more detail on something just drop it in the comments below or send us message. We love the fact that as soon as our engine gets hot we’re heating water as a by-product. We would definitely not hesitate to do it again.

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