Max temperature of polyethylene water tank?

[Vannautical engineer]

Good luck, let us know how it works out for you! In my opinion a heavy insulated cooler will work best as a water tank as long as you seal and vent it. Another plus is it is easy to clean the interior or replace if necessary. I never use hot water for drinking or cooking.

Yes I'll start another thread at some point to outline my whole build. But this thread has made me lean more towards just using the hot water directly from the exchanger rather than trying to store it in a tank.

I will probably still need some type of recirculation path from the heat exchanger back into the tank, because the heat exchanger is mounted underneath the vehicle, so I was planning to program the system to circulate water or coolant through the exchanger any time the temperature got close to freezing to prevent having water freeze inside the exchanger if I'm ever in cold climates. (I'm also putting in a manual drain valve underneath the van so I can totally drain the water if I need to in order to prevent freezing.)

Yes this is a pretty ambitious system for heating water, but if I pull it off I think it's going to be pretty neat. 

 

[highdesertranger]

I think you're making taking a shower way to complicated. So basically the only time you will be able to take a shower is after a long drive or shortly afterwards. Without hot water flowing through the heat exchanger(engine running) you will soon cool the water off so there will no more heat exchanged. Running your engine to ONLY take a shower is very inefficient.

For about 10 years I either just pay to shower or heat water on my stove and put it in my weed sprayer shower. You are going to have a stove, right? Soon I will have a regular shower with a water heater and a full size shower.

Highdesertranger

 

[Vannautical engineer]

I make everything way too complicated. 

There is going to be an electric coolant pump so coolant can still circulate through the exchanger when the engine isn't running. Honestly I wanted to have this anyway because I'm not confident on relying just on the water pump to pump coolant the whole way to the back of the van where the exchanger is mounted. So yes especially if I use hot water directly out of the exchanger, the only time I will have hot water is when the engine is hot, but being able to circulate coolant even with the engine off means that I will have hot water until the engine is cooled back down.

Pretty much the only thing I was not willing to compromise out of this build was having some way to take a shower. Without that, I feel like the van is not doing all that much more for me than giving me a place to sleep.

As far as propane, I don't want it to have any part in this build. The cabin heat is going to be coming from a gasoline Webasto, so no propane needed there. And with the size of the van, there just isn't room to fool around with storing propane tanks, and I don't want to mess around with filling them.

I actually have no plans for a permanent stove in the van. Again space is limited, I don't do a lot of cooking, and this will mainly be for long road trips instead of full time living.

 

[bullfrog]

The one thing no one seems to consider is how much water weighs, the amount of heated space it takes up and how tempting it is to soak in a hot shower not to mention the gray water issue in some areas. My wife and I usually can only make at best 14 days on 50 gallon tanks.

 

[Freelander]

I believe this a feature found on some Winnebago RV's from a few years back, as I remember they had a patient on it, and they were the only ones that used this type of setup.

 

[Vannautical engineer]

I've already fully accepted how much weight it's going to add, and how much space it's going to take up. It's a lot of the reason I went this route and I'm not keen on other things like having propane, a standalone water heater, etc.

This was the only way to reasonably get hot water in such a small vehicle without having a huge amount of the cargo area being taken up by the water and all of the stuff needed to heat it.

 

[bullfrog]

Years ago we used a two room shower tent with a tarp under it to act as an evaporator for the grey water. If that wasn’t acceptable because of humidity and insects we used a concrete mixing tub and blue boy to dump it. Funny come to think of it when I had a VW van we raised the rear hatch, hung a tarp over the hatch, sat a solar shower bag on the roof and stood on an old modified pallet! Lol!!! Showers were quite the event!

 

[XERTYX]

I have used the weed sprayer shower route many times before. I had 2 1 gallon water jugs from the grocery store that I spray painted black. Set them in the sun a while then dumped them into the weed sprayer and had a glorious hot shower.

The last weed sprayer I bought had an integrated high pressure blow out valve that screwed in and out. Maybe an inch or so threads. I have kicked around the idea of seeing if a heating element would screw in there. A 125 watt element heats a few gallons to 120° in an hour. 90° after half an hour shouldnt be too much to ask. A little more than 60 watt hours well spent if ya ask me. Call it 75 watt hours. That's reasonable with most systems.

 

[XERTYX]

Oh, something just occurred to me. I know you said you didnt want to use electricity to heat water (very wise), but you did say a transit yes? Don't many of them have a prefab system to operate a battery Isolator? If you're going to be doing enough driving to justify a heat exchanger couldnt you still use an electric element? If you're driving enough daily to consistently heat a closed hot water system greater than 140° to kill bacteria then wouldnt you be driving enough to recharge the house batteries while also heating a small tank of water for 1 shower?

 

[highdesertranger]

You keep mentioning space, if you have such limited space where are you going to take a shower?

Where is the grey water going to go?

How many gallons is your tank? What is the GVWR of the van and what does it weigh now?

How many gallons of coolant does your engine hold? if it's like most modern vehicles it's very little. Your idea of circulating the water without the engine running is going to cool the engine water fast. What are you going to do when the engine thermostat closes stopping circulation?

Where is this heat exchanger going to be located? If it's inside the living space along with a hot water tank, in the summer it will make the inside of the van very hot. If it's outside the living space in the winter it's going to cool off very fast.

Do you realize that you really can't alter the temp off the coolant very much. What I mean is your heat exchanger can not make the van's coolant run much cooler. The computer won't like it.

You know about Murphey and his law. it's usually best not to invite him along with one off custom stuff at first.

Sorry about being a downer, I am just playing devils advocate.

It is my opinion that at least at first you should try to keep everything simple. Get on the road and see what you actually need first.

Having said all that I do like the idea and I hope you report all your findings here. Good luck.

Highdesertranger

 

[Freelander]

Also most newer engine are built to run hotter than the 140* you are looking for. Another thing to look at is if the water is pumped to fast the heat exchanger, it won't have to time to heat your water in your tank.

And it will probably take for ever for your motor to heat with all that extra water to heat up.

 

[XERTYX]

Ever the voice of reason HDR. You seem as I to think it's not impossible. Merely an engineering hurdle. Maybe there is an easier way. Weed sprayers make for a wonderful shower. I even used to use mine with my portable washing machine. I connected the water line to the inlet on the spin cycle for rinsing.

Transits are wonderful. I have ridden in them and the whole time all I could think of was what I could do to it. Haha. But what they boast in terms of overhead space they seem to be rather short in terms of length. Space is very limited.

I think HDR makes a great point. Build it out moderately and take a road trip to a park. Try living in the space for a weekend and take a notebook. Take notes and evaluate what you're missing and how to remedy that. My first weed sprayer shower I built for probably less than 20 bucks. Take one with you. See if you can get by with that.

Dont discount cleaning yourself with a spray bottle also. One of the most thorough showers I ever took was with a spray bottle when I only had about 2 gallons of water to my name and needed it for the shower as well as cooking for about 3 days until I could get more water.

 

[Vannautical engineer]

You keep mentioning space,  if you have such limited space where are you going to take a shower?

Where is the grey water going to go?

How many gallons is your tank?  What is the GVWR of the van and what does it weigh now?

How many gallons of coolant does your engine hold?  if it's like most modern vehicles it's very little. Your idea of circulating the water without the engine running is going to cool the engine water fast.  What are you going to do when the engine thermostat closes stopping circulation?

Where is this heat exchanger going to be located?  If it's inside the living space along with a hot water tank,  in the summer it will make the inside of the van very hot.  If it's outside the living space in the winter it's going to cool off very fast.

Do you realize that you really can't alter the temp off the coolant very much.  What I mean is your heat exchanger can not make the van's coolant run much cooler.  The computer won't like it.

You know about Murphey and his law.  it's usually best not to invite him along with one off custom stuff at first.

Sorry about being a downer,  I am just playing devils advocate.

It is my opinion that at least at first you should try to keep everything simple.  Get on the road and see what you actually need first.

Having said all that I do like the idea and I hope you report all your findings here.  Good luck.

Highdesertranger

I appreciate the input, but really I think I have everything fairly well considered.

I have a little bit of space set aside that I should be able to shower in. It won't be a permanent thing, but probably using a collapsible basin I can fold away when not in use.

The payload capacity of the van is 1600lbs. Even with the water tank full, I estimate that my total build is only going to add about 600lbs to the empty van. I'm being pretty conscious about weight in the build, and not using a bunch of heavy materials.

The heat exchanger is going to be tapped into the heater core circuit of the cooling system. This circuit of the cooling system does not run through the thermostat. So theoretically if coolant kept circulating with the engine off, the coolant would only cool off once it pulled all of the heat out of the engine block itself. I think that's plenty of stored heat. And honestly, even if I had to keep the engine running to have hot water just for a shower, it's a 2.0L 4cyl. It's not like I'm going to be idling some huge V8 here. I'm not too worried about it.

The heat exchanger is mounted underneath the vehicle. I did not like the idea of running hot/pressurized coolant into the living area in case of leaks. I plan to have the system automatically circulate fresh water and/or coolant through the exchanger if it gets near freezing to prevent it from freezing up, and I'll have a drain valve underneath the van if I really want to be sure it won't freeze up. It's probably going to be for mostly summer time traveling anyway, but I am building it to be able to handle the cold too.

I don't think having this heat exchanger will alter the temperature of the coolant too much. Again it's going to be on a circuit of the cooling system that doesn't run through the thermostat. So if the heat exchanger actually removes so much heat that it begins to cool down the coolant, the thermostat would close, cutting off flow through the radiator.

So to really cause a problem, this heat exchanger would need to remove so much heat that the engine still doesn't warm up with all flow to the radiator cut off. I don't see it happening. Even if it does, maybe in the most extreme case, it would throw a "failure to maintain engine temperature" code similarly to when you have a thermostat that sticks open. But that's about it. No big deal. Clear the code and move on.

Yes I know this is a pretty complex idea, but I really think I can get it to work. And if I do, it will be a great way to get hot water without propane.

I'll keep people updated, but I don't anticipate getting the whole system put together for another few months. Currently I'm working on the rest of the inside of the van, and the cold weather is going to keep me from being able to work on it these next few weeks.

 

[GntlStone]

It's certainly possible to do what you're looking to do. George over at Humble Road, a custom van builder out of New Jersey, has done it in his last two or three vans. I believe he uses an Ecotemp heat exchanger and a small expansion tank. His videos go into the process a bit. He is likely available to consult with you and give you an idea what he's doing/done. Check out the tour of his last build for an overview of his system, if I remember right. https://m.youtube.com/channel/UCE9t...FjADegQIEhAG&usg=AOvVaw0ZHKZC-krXOkdjYLtNiHRS

Also Van Life Tech has an infloor hydronic heating system that uses a heat exchanger. They're at https://www.vanlifetech.com/

Both rely on a large lithium battery system. Check out BigBattery for good batteries, they provide alot of watts/$. They do 12v & 24v systems. Their new Extreme series has included fire suppression. https://bigbattery.com/

You might be able to get more solar on the roof than you think, especially if you can rig a panel system that stacks and slides out, like Everlanders. https://everlanders.com/

 

[Vannautical engineer]

I checked out the video of the Humble Road van. That van has some really incredible craftsmanship. I love it. Mine is not going to be on that level.  :s But hopefully I can get this hot water idea to work the way I envision it.

 

[bagabum]

Vannautical engineer, it only takes a gallon of water to take a really good shower and get clean, more water is for fun. My perfect shower temp is 110 deg F. 1 gallon.  8.33 lbs x 40 deg delta T = 333 Btu. So 333 Btu/ 3.42 Btu/watt = 97 watts. Just purchase a 2 gallon insulated water jug, add a  gallon of water , drop a 100 watt heating element in it and after driving for 60 minutes you have shower water that will last for hours in the insulated jug.  Keep it simple man, like HDR and others with decades of experience  have said. Cutting your coolant water hoses??​

 

[XERTYX]

 Cutting your coolant water hoses??​

To be fair there are plenty of heat exchangers that do exactly what he's proposing. The only difference is that they're normally in bigger rigs and for a much larger wallet. They're into the thousands usually.