Recirculating shower warm up time

[MsNomer]

I think you are going to have to consider yourself a pioneer here and do your own testing. Even in the RV/camper world, recirculating showers are quite rare, probably because of filtering complexities. Folks just tend to accept either the navy shower or the large tanks or the frequent fill up.

OTOH, I don’t see why your question cannot be addressed by folk who don’t recirculate. You need to heat a couple gallons of water. It doesn’t matter whether you navy shower with it or recirculate it for a longer shower.

Heating one gallon of water by 1 degree F requires 2.42 Wh. Plug in the specs of your heat source, and you should be able to calculate time required, which will obviously vary with the starting temperature of the water.

I know many people in the van world. I don’t know anybody who heats water with 12V. If you have access to AC where you stop, a Sous Vide functions as a convenient, compact, efficient temperature-controlled electric heating element. On average, it takes me about 15-20 minutes to heat 2.5 gallons to our preferred 105°.

 

[booster]

MsNomer's calc gives nearly identical results to mine so probable accurate.

 

[GeorgeRad]

.....

OTOH, I don’t see why your question cannot be addressed by folk who don’t recirculate. You need to heat a couple gallons of water. It doesn’t matter whether you navy shower with it or recirculate it for a longer shower.

........

Good point, heating one gallon of water is equal to heating one gallon of water in our universe.

 

[booster]

Good point, heating one gallon of water is equal to heating one gallon of water in our universe.

Yep, and as soon as the actual system was defined it all got easy.

 

[phantomjock]

Unfortunately the van is usually the TOAD in these situations. .... Trying to keep it self contained and portable for removal in cold temps.

You seem focused on "recirculating" as part of the solution. I'd opt for the "Tankless solution," and refill the van main water tank as needed. It could simplify your approach, and because it is a conversion van - you might know all the bits required to install.

My thoughts:

1. Mount the heating unit in the van.
2. Plumb in water valves to the existing system. The pump in the water system will determine the rate of your shower
3. Add a dedicated propane line to the rear of the van, appropriate valving etc.
4. Carry an external propane tank on/in a bumper style cargo box​

You'd need to valve into the existing water system, and add a 12volt circuit to light the system. The pic shows the switchology of the tank.

When we were cruising, we did a similar approach to have ready access to hot water at the galley sink. Admittedly, we had much more water and propane than in the van, but our process was:
1. Open the water supply to the tank,
2. Check the propane valve open
3. Turn on the "Dragon" (Ignition)
4. Within a few minutes we had hot water on demand. No recirculating required.
Our tank was located about 8-10 feet from the galley sink, the propane line about the same where we connected, and the water fill about 2 feet from the aft head sink. Heating time was minimal, the price around 200 bucks, and we used it for years.

Cheers - Jim

 

[Dave01a]

No existing water tank or propane. This is a from scratch install, and hanging a propane tank on the outside for an occasional use shower.is not desired. FYI, those tankless systems have to be used outside or vented. And outside in the middle of a snowstorm is not happening.

I have a tankless at home so I completely understand the system. A true recirculating shower for the van 0is the target.

 

[jrobe-ClassB]

He said long ago that he doesn't want an inexpensive propane solution for an occasional long hot 12 volt shower with recharging as he tows his van. I am looking forward to reading in the future how he designed it since no one else has done it. LOL

 

[Dave01a]

The system is pretty straight forward. Two level portable shower pan creating a small reservoir on one end. Pre-filter ahead of the 12V self priming pump, 50 micron filter, 10 micron filter, 12V UV filter, then the heating element in a 2" copper pipe of appropriate length before going up to the shower head. Depending on the pump gpm, may have to put two of the smaller UV filters in parallel.

With the heating element being the last in the process, there is a possibility of using a heat exchanger from the van, but that would limit the transportability short of some good disconnects for the shower connections. Keeping the temp cool enough to not be scalded from engine temps is another factor.

As I said, the main hardware will fit in a decent suitcase sized enclosure. Add the base / reservoir and a hand held shower an it's all set. A few have tried different specialized enclosures for the heating element, but copper is a simple solution. It also allows the option of a standard external thermostat and high limit instead of the expense of a heating element with an integrated thermostat.

 

[GeorgeRad]

Interesting project, I am looking forward to see an actual design on a paper. I still don’t know what is your question but it seems you have good answers to all your questions. While in your design phase in addition to UV filter you could consider an ozonator, an activated carbon filter, a diatomaceous earth filter and ultimately reverse osmosis.

 

[Dave01a]

I have yet to see any designs with an ozinator instead of a UV unit. I'm familiar with what they are, had one on a spa once. It took the place of chlorine for treating the water. My understanding is the UV filters have superseded that technology in killing anything growing in the water. With UV units now using LED technology, they are pretty much the go to unit for size and efficiency.

This is not a pass through system, but a closed loop that will be drained and refilled as needed. Particulate filtering and bacteria elimination is all that is required.

 

[phantomjock]

As I said, the main hardware will fit in a decent suitcase sized enclosure. Add the base / reservoir and a hand held shower an it's all set. A few have tried different specialized enclosures for the heating element, but copper is a simple solution. It also allows the option of a standard external thermostat and high limit instead of the expense of a heating element with an integrated thermostat.

So, with as much thought you have into a solution, could you sketch it out? A picture is worth...

Permit me to ask (maybe again) - why a recirculating system? Seems like it over complicates your simple requirement for an occasional shower.

What do we know about the shower system you are seeking (in general) and what is known:

1. Pump CFMs are readily available. You can answer that quick enough. Let's say 5 gpm (but you can cycle onn/off to conserve.
2. A "Navy Shower" uses less than a 5 gallon jerry jug --oops thats 1 minute and empty...
3. So now, the system is larger than a "suitcase." Jerry Jug > suitcase, or 2
4. Energy requirements - You mention reheating & scrubbing of circulated water. Do you have an idea how many amps required? Wow! I would have never considered that on my 1400Ah system on my sailboat! UV sanitizing - maybe not in a 12v world.​

You are seeking a "recirculating" system that could exceed the energy budget. And, the space you are suggesting might not be large enough. Maybe time to revisit the "requirement."

If what you need/want is an occasional shower with hot water, why must it be recirculating?

A larger system that might provide you with an occasional shower, be self contained, removable and stored when not required, but larger could fit into a larger hitch mount storage box. It would be able to contain a propane tank, water pump, water supply and tankless heater. But, it wouldn't "recirculate." All waste water goes down the drain. And you would need to be frugal in using the water.

Sorry.

As much fun I have had with this thought experiment - I wish you best of luck in finding what I would describe as a ""Unicorn."

Cheers - Jim

 

[Dave01a]

I asked a simple question for people that already have on in use. What is your real world warm up times like, with the relevant data to go with that.

That's it.

There is no off the shelf unit that I'm aware of, so every system is going to be slightly different. Factor in those differences, and I have my answer.

The less water you have in the system, the quicker it warms up to operable temps. Pre heat the water in someway, again quicker operating temps.

I will be constructing the system not too far down the road, but wanted a bit of a heads up. Kind of a 'wish I had / wish I hadn't' thing.

And while I appreciate all the opinions tossed out there, across six different forums I have yet to get a response from an actual user.

BTW, there are a number of good 12V UV units out there now, With LED technology, it's only around 2A.

 

[GeorgeRad]

You got one good answer from this forum, do your homework and check your principle objectives.

 

[Dave01a]

GeorgeRa, I saw your post discussing a non-recirculating system on your sail boat. At least that's what I got out of it. And many discussions and agreements on the calculated heat times. But I have not seen any responses on actual recirculating systems with specs from real world users. I won't say I might have missed it, so point it out if I did.

Calculations are good, but not the be all end all for real world information.

 

[GeorgeRad]

GeorgeRa, I saw your post discussing a non-recirculating system on your sail boat. At least that's what I got out of it. And many discussions and agreements on the calculated heat times. But I have not seen any responses on actual recirculating systems with specs from real world users. I won't say I might have missed it, so point it out if I did.

Calculations are good, but not the be all end all for real world information.

You myst be mistaking, I never had a sail boat.

 

[Dave01a]

Quite possible. I remember a post talking about using a diesel heater on a sail boat. It's hell getting old when your memory was bad forty years ago. Skipping across several different forums probably doesn't help.

 

[Snowy-ClassB]

But I have not seen any responses on actual recirculating systems with specs from real world users. I won't say I might have missed it, so point it out if I did.

You keep complaining that you are not getting any feedback from people who have a system like the one you propose. At the same time people on this forum keep telling you that your concept seems unreachable. Maybe the reason no one has experience with such a system is that no one thinks such a system is worth building.

 

[Dave01a]

Plenty of YouTube videos out there for this system.

 

[booster]

Plenty of YouTube videos out there for this system.

If there is that much information out there on this type of system, why is the very basic information you want not available on their videos or by contacting them?



YouTube is kind of famous for people making videos of many different things with inadequate information, data, or testing of them except some anecdotal "it works great" type things. Many lithium battery and solar installation and use ones come to mind as an example.



As you have seen, this forum thrives and survives on data, testing, and detailed information and IMO that is necessary in most of this kind of stuff.


There have been lots of things presented on here that are odd and unusual from many members, certainly me included, but help and feedback help get to the final decision on if it actually works, or not. This explains why that nobody here was willing, or able, to answer the original question with not enough information given to determine that answer, in their opinion.


My guess is that nobody here knew enough of the system to determine if they ever had personal experience with one or had ever even heard of one, there is no way to answer the questions.

 

[MsNomer]

“4. The all important question, rough heat up time. From fairly quickly, to go out and pick up a sandwich while it's pumping and heating up.”

“I asked a simple question for people that already have on in use. What is your real world warm up times like, with the relevant data to go with that.”

We adequately answered your “all important question” even though we don’t recirculate. For the others, ask the YT’ers.