Water Heating System Advice - Off Grid Full Time - Need your help

[TheBusHome]

Hello everyone sorry for the long message, trying to give as much info as poss to aid anyone able to help. I've tried to find similar thread/system/solutions but none exactly the same so hoping for some advice (or if you know its definitely elsewhere, feel free to point me towards it.

Looking for water heating advice and methods. Bus not obtained or converted yet so in planning/design stages. I’m basically looking for the simplest and most cost effective way of having cold water from the cold taps (easy peasy) and instant hot water from the hot tap (ideally limited to a non-scolding comfortable temp).
________
Notes that may help(if i missed anything please feel free to ask).
- System is Kitchen sink, bathroom sink, small bath, shower over bath.
- Cold water feed from grey water tanks.
- Will be living in full time off grid.
- Bus will hopefully have solar & batteries - I know I’ll need to factor in any suggestions that involve power consumption.
- Am strongly considering wood burning stove as main heat source for winter.
- There are sufficient grey water tanks for the above.
- The bus will have a 240V AC and a 12V DC supply.
- No propane needed so far, but if needed for this I can factor it in if its cheaper to do that than have it run off the solar power system - although i’m ideally aiming towards having no bills/ongoing costs both now and in future so if I can avoid propane that’d be ideal - but it is what it is, if it is absolutely necessary to achieve best result then so be it.
- sinks, bath and shower are all within a few feet of each other to minimise pipe runs.
- Sorry if me using Metric offends anyone, I'm from an engineering/technical background and in the UK. I've got a convertor for anyone using imperial so go with what's easy for you and what you know and I'll convert it

Goals:
- Cost to minimum (goes without saying).
- Fast (ideally instant) hot water on all of the below items on the system.
- Simple, minimal equipment - less to fail or maintain.
- If using a water heater of some kind, absolute minimal power consumption so not to need a lot more solar and batteries.
- Take up as little room as possible obviously.


Really looking for advice from those who have similar, what you did, what you would’ve done different, advice from your experience, advice from experts, plumbers, innovators, engineers, DIYers, and equally from inexperienced who learned the hard way or from others - basically open to anyone's advice regardless of experience as we all have something to offer in some way

My limited thoughts/idea so far but nothing is decided or set, so very open to your inputs:

1. Water coil in stove pipe? (that will come into play in cold weather but as a secondary method as wouldn’t want to have to use the stove in summer just or hot water and end up having an accidental sauna haha
2. Instant tankless hot water heater that feeds them all? (eccotemp or similar?) Or do these consume too much power and cost a LOT of money to buy and run or maintain / reliability issues?
3. Somehow have solar feeding in if there is excess input from the solar/batteries? iBoost? or would I need the grey water tank to have to be capable of holding hot water meaning potentially i would either have times where i didn’t have cold water, only hot (not ideal for teeth brushing or if cold water is needed) or would have to have a separate hot and cold water tank (which is not an option).
4.

Extra Notes (in case they're relevant):
How much water is used use:
Shower - 350 litres per week per person. (needs to handle up to 700 litres per week for when we both live full time).
Bath - 200 litres per week once my girlfriend starts to live on full time so planning in advance.
Washing Dishes & Brushing Teeth - 45 litres per week
(May be entirely irrelevant but there is a Washer/Dryer for Laundry (approx 50-120 litres per use) - but cold water fed only from its own grey water tank so no need to consider in terms of heated water). - Ignore washer dryer if irrelevant.

[dan-fox]

You've just spec'ed 250 US gallons/week before washing clothes (or cooking?) That is a lot of water. 945 liters of water weighs 945 kg. That is a lot of weight. Are you planning to travel a lot? be hooked up to shore utilities? Fill this beast with 22 40 liter totes full? Electric hot water is only feasible while hooked to shore power; solar electric hot water is even less feasible than solar electric air conditioning (which is marginally possible).

Keep in mind that if you carry that much potable water you have to put it somewhere, so you'll need a comparable amount of gray (grey) water storage.

All in all, there are better strategies. Here in the States one strategy is to maintain a basic-level membership in a popular chain of fitness centers, just for the showers. If you are in a campground, there are (possibly tolerable) shower facilities there. Learn to tolerate sponge baths. Learn to tolerate bathing every other day.

Instant-on tankless water heaters seem to be popular, followed by pans on the stove. The tankless heaters are much cheaper to run on propane than electricity. Off-grid, hot water will only come from combusting something. A tankless setup puts a premium on short pipe runs (which you seem to be aware of), and/or the additional complexity of preheat pump loops.

My tuppence worth.

[Twigg]

You will need a full-service hook-up at a campground to even get close to making this water plan work.

Most RVs carry 50 to 100 gallons of water.

[TheBusHome]

hey mate, thanks for replying yeah I've seen a lot only putting 50-100 on but it won't be enough for how I want it to work. I'll have access to be able to fill up as I won't be travelling a ton. I've spec'd it for my specific needs and calculated it pretty accurately. Luckily I won't need a full service hookup, although there will be the provision built onto the bus for times I rock up to any grounds.

[TheBusHome]

hey dan-fox. I just typed out a lengthy reply to yours and clicked 'post' and it logged me out and vanished! logging back in didn't help, neither did clicking back in the hope it was there aargh. Thanks for your reply and input, I'll retype what I wrote in a few minutes when I've stopped giving my laptop the side eye! Stupid timed log out, whyyyyyyy. haha.

[Twigg]

Originally Posted by TheBusHome

hey dan-fox. I just typed out a lengthy reply to yours and clicked 'post' and it logged me out and vanished! logging back in didn't help, neither did clicking back in the hope it was there aargh. Thanks for your reply and input, I'll retype what I wrote in a few minutes when I've stopped giving my laptop the side eye! Stupid timed log out, whyyyyyyy. haha.

When you have typed your reply, copy it to your clipboard and if it happens again you can paste it into a new message.

[TheBusHome]

Bit late now mate hahaha learned the hard way. That’s why I tried the back button in the hope to do just that but nope lol

[TheBusHome]

Hey dan-fox, thanks. Yeah I know it’s a lot of water, way more than usual but it’s what I need for what I’ll be using it for. The purpose of this particular build is not really for travelling, it’s to essentially be an apartment but with the added bonus of being able to move or it needed in future. The beauty of skoolies is being able to do all sorts with them (within reason). I realise it’s 1kg per litre of water and so if I need to move the bus (rare), I’ll just do a dump of the grey water and refill when I get to destination to prevent sloshing and reduce weight by essentially a 2 tons. (I designed it to be equal weight either side of the Bus. It’ll make sense when I reveal the plans at a later date on the YouTube videos and fb/insta pages but saving that for when the build starts.

So to answer your mind repaonses: it’s not really for travel otherwise I get what you’re saying and you and Trigg would be right, smaller tanks would be more suitable to prevent sloshing and obviously less water needed. The purpose of this is to emulate an apartment and not need to rely on a hookup often - although I will have easy enough access to refill every couple of weeks or more.

Point to note, myself personally, i’m lucky enough to not need to shower daily and still stay fresh, so I don’t need to shower daily plus I’m happy to love minimal including water provision BUT I’m factoring in my girlfriend needs a slow intro to Bus life so this first bus will need to work close to living in an apartment to slowly transition. A future build will be different but this one is being designed for purpose so I totally understand a few RVers and skoolies may wonder why I’ve provisioned for so much water. As with the solar, the ideal plan is to be able to be off grid for as long as possible without relying on any connection and a realistic compromise is 2-4 weeks without needing to fill up. If it’s juts me living onboard I can go weeks on that amount of water, like loads.... but if we both live on, it’s around 2 weeks and that includes being able to have a couple of baths, for her to shower daily because she works at a vet so gets animal blood and unpleasantries on her daily as well as general muck from the stable. Hope all that made sense. It’s not the expected norm but it suits what the ideal goal and need is for this one.

I’m planning on having a mains generator so there should be 240v running from a silent generator somehow and hopefully that’ll be hooked up to be able to charge the batteries if needed. Hoping that can run the instant hot water for the duration of a shower or a quick blast to clean a couple of dishes here and there.

Good to note about the propane though, if you think it’ll be better to run the tankless off propane instead, If I need to go down that route I can factor it in and put the tanks in undwrstorage somehow just for the that. I was considering it for a 3 way fridge but holy moly are they expensive and the Thetford one I looked at consumed almost 4 times that of the home one I have which is only 311kWh per year. The 3 way is 4kWh per day on paper! Swings and roundabouts I guess, more flexibility, but uses more power, could run it off propane but then need to buy propane. If I can run it off the battery/solar then that’s ideal scenario. But digressing....

Like you’ve said, I know there are better strategies, totally. This one suits what I need on this particular build but if I was doing a build to be able to travel regularly with it I’d put in much smaller grey water tanks to prevent slosh and reduce weight and factor in more stops for refilling, etc.

Totally right with the gym membership and I have that as one of the options on my original plan, not ruling it out in addition - I can get one that has gyms all over the U.K. for around £15 per month which is cheaper than camp sites plus I’d get gym access, but I also want to not need to rely on that and as mentioned it’s a factor to be an inconvenience to my girlfriend who needs to adjust slowly to Bus life rather than a full on shock. For me, I’m used to deploying away from home and family for short or long periods or living basic in a single room or confined space but she’s never been away from family or loved alone or with almost no provision so just easing towards that- slowly does it.

Regarding your last comment about combusing and preheat pump loops - totally over my head, happy for you to expand on that mate. I have construction experience in electrics and framing, tiling, kitchen and bathroom fitting but when it comes to plumbing I have zero clue hence this request for advice so your comments are totally and genuinely appreciated. Sorry that was long winded, I’ll try to keep them much shorter in future.

[rossfree]

I have a tankless on-demand hot water heater running on propane. Heating much of anything with solar is somewhat impractical on small scale solar. The tankless heater is economical and takes very little room. I set mine for shower temperature so I don't even fiddle with knobs. That saves precious water when you have a limited supply.

Regards!

Ross

[TheBusHome]

Hi Ross, that sounds awesome. Which one are you running? Setting to shower temp sounds ideal.

Couple of questions. For you if you don’t mind.
1. What are you running off it? Shower and sink?
2. Do you know roughly how much propane is used up for what you’re using? And follow up question roughly how many showers/sink fulls for how long? Sorry for the amount of questions. Eg like 4 showers and general dishes = X litres/gallon propane tank a week or whatever.

Thanks so much for your input mate

[miscrms]

Tankless propane is really hard to beat IMHO. The ~$400 Eccotemp 45H has a 150,000 BTU/hr burner. That's 44kW in round numbers. I'm also trying to find a way not to have to use propane, but this one is really hard to overcome. Solar would be really nice, but pumping large amounts of water through collectors mounted on the bus roof seems highly problematic. Using an electric tank based water heater, and primarily using your excess solar electricity to run it is also an appealing thought if you have room it.

One of the challenges with water heaters in general is the water in the pipes gets cold and has to be flushed out before you get hot water at the tap. This is a little worse with tankless as it takes a second or two for the burner to fire up. While this is somewhat acceptable at home, it can be a major source of waste that is much more problematic on a bus with limited water resources.

One solution is a recirculation loop. This typically requires another return line from the hot line at the furthest tap to the cold input on the heater. An electric pump in this loop is run periodically (either manually or on a timer) to preheat the water in the hot supply line, so you get hot water more or less immediately once you open the tap.

If you can keep your lines between the heater and the taps very short that will at least minimize the amount of waste, but co-locating the heater and the places you need it is not always easy.

Rob

[TheBusHome]

Hi Rob, thanks for your reply. Some great info in there mate. I get what you’re saying about the tankbased and solar electricity offset, sadly I won’t have enough room for it on this specific build. Living in England would also mean I’d have to highly insulate it as it’d have to be under the bus and would probably be cold by the time I used it knowing my luck haha

Totally understand what you’re saying about the little bit of cold water stationary in the pipes, my sinks and shower over bath are all within about 3 feet of each other (or closer to about 5-8 feet in terms of pipe runs) so it minimises it but still has it for that short run which as you say in a bus it’s still a waste of a litre or 2 of water each time which could’ve washed a couple of dishes or been used for brushing teeth/washing hands so I guess one way to get round that is to collect it and somehow put it back into the source tank with a jug into a plant watering can or something like that I guess. Or the loop method like you mentioned seems like a more seemless plan.

One factor for me though, I spoke to Eccotemp live chat tech support guy last night who was super helpful but he was saying he’d recommend the i12-LP, the downside being I won’t have 120V supply because I’m in England it’ll be 240V so obviously I’d now have to factor in also having a 120V supply just for that. I asked him about the IE range of electric eccotemps that are 240V, thinking that might be an option for me if they didn’t do a 240V start LP version (because they don’t seem to have an indoor version that starts off 2 D Cell batteries) and he said the IE 240V models pull 150 Amps. I’d mentioned I’d have solar electricity and he said it’s probably not suitable - I didn’t expand on that part of the conversation because 150 amps... wow! We then discussed that they have he L10 & L5 outdoor models which only need 2 D cell batteries to ignite (which I guess I could mount under it on the back of the bus outside in an enclosure and he said it’d be fine even though I asked him about RV mount etc (and I later found the product manuals to state not to mount any of their products on motorbikes or RVs). His solution to that was to have a way of disconnecting the inlet and outlet so I thought maybe I could get the plumber to fit one of those push fit gas plugs on a short piece of flexi-gas pipe like some ovens have, and same with the water pipe maybe. Need to work that out properly with a plumber so open to advice on that too. My biggest concern with that though was in the manuals it said not to have the unit anywhere there are flammable fumes that can get to it - now I planned on it being in a ventilated cabinet under or back of the bus and it made me think about when I’m filling up the bus with diesel - I’d have to remember to disconnect and air it so I didn’t blow the entire bus and filling pump up haha yikes! So I may need to look at other options unless I can figure out having a 120V supply just for the indoor model i12-LP without it causing any problems or pulling too much power off the solar panel/batteries. I feel like I opened a can of worms with this part of the build haha

Co-locating the heater with the sinks will be easy if I can use the indoor model because I just altered the floor plan to be able to put it into a hidden cupboard by making one of the bathroom studded frames walls a little thicker and just vent pipe it out the side of the bus.... but again, concerns me being such a small space with what it says in the manual unless they’re being over cautious - I guess carbon monoxide and fine detector indicators could be used to monitor it but hmmmmm oh and he suggested the L10 or at a push the L5 but again their manual says they aren’t designed for permanent use only portable so I don’t know whether that’s purely marketing speak to get people to buy the other models for permanent installs as they have a full range or whether the portable is only designed for occasional use - although I did see a few reviews of problem saying they use theirs permanently in a small home and it’s worked great for years so...

I may need to look at an alternative to eccotemp maybe, or come up with methods to get around the limitations on the eco temp so if anyone has any suggestions, alternatives, experience or knowledge with this stuff feel free to let me know if you haven’t fallen asleep during my reply that is haha

[lucasd]

There are also a few tankless, on-demand hot water heaters that are specifically designed for RV use.

Girard brand
Girard Tankless LP Water Heater On-Demand GSWH-2 - $506.40
Suburban brand
https://www.pplmotorhomes.com/parts/...heater_09-0047

I don't endorse either product or supplier, as I don't have any experience with any of them, but they are out there as options. Pricing looks like around $500-$600.

[TheBusHome]

Lucasd, you’re a legend thank you. I’ll take a look at these too as options

[Tango]

It is easy enough to split 240 and have 110. Even a cheap international travel "converter" would let you plug 110 into 240. Just a thought.

[Rusty]

Originally Posted by TheBusHome

Living in England would also mean I’d have to highly insulate it as it’d have to be under the bus and would probably be cold by the time I used it knowing my luck haha

Wouldn't it just be easier for you to move over here to the States?

[TheBusHome]

Tango, yeah you’re right. I just need to make sure it doesn’t add any additional inefficiencies considering the solar / battery bank to make sure I do it right. Thanks for your reply

[TheBusHome]

Well, Rusty, hahaha yeah it would be so much easier and if my girlfriend was open to it we would like a shot haha it’d certainly save me a lot of cash on the build in general tbh haha we had joked about it before for other non bus related reasons but I doubt she’d go for it *sad face*

One example - it’s cheaper for me to get and import a US Skoolie than it is to buy a bus in the UK. Skoolies seem to have low mileage like 70-200k tops from what I’ve seen. U.K. buses don’t get retired until they’ve got like 10 times that on the clock and even they they sell them for at least 4 times what you can get a Skoolie for and they’ve probably had about 4 engine replacements in that time haha they get hammered.

[miscrms]

Yeah, the 45h is probably oversized for most bus needs. I’m looking at that one because I’m thinking of using it for heating too. Mostly I was using the example to show how hard it is to beat tankless gas on a btu/$ basis. As you discovered electric on demand is pretty much a non-starter. It takes lots of kW to get enough btus.

The portables are probably a good option to be looking at. Their size should be easier to mount. The D batteries mean you don’t have to worry about the power issue. You could even hard wire pretty easily with a small dc power supply (probably 3v if the two batteries are in series) which you could source locally to be compatible with your power standard. The current/power demand should be very low as they are only used for the igniter to start the burner, so a small cheap generic “wall wart” type power supply should work fine.

Exterior mounting is highly desirable in my mind for several reasons. You don’t have to run gas into the interior unless you need it for other purposes, so you reduce the risks of carbon monoxide or leaks. Also you’re not consuming breathing oxygen for combustion, and not putting the moisture that results from propane combustion into the bus which can contribute to humidity / condensation problems.

If you are using diesel you shouldn’t have to worry so much about combustible fumes. If you have gasoline you will want to give more careful thought to locating the heater away from the filler and fuel lines, and maybe ways to lock out the heater during fueling. If you hardwire it a simple switch to shut off the power would be effective. And probably a good idea anyway as those wall warts do draw a certain amount of wasted power when not in use.


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[miscrms]

The RV units are probably more convenient to work with, as it’s closer to their intended use. The only down side is cost. They have about the same power as the small portable units, but cost more like a big household unit.


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