Talk me out of an air pressurized water system...

[dieselBlazer]

I have an old K5 blazer that I added pressurized water to a few years ago and I like it. Its a simple system using a single 5 gal water can on my bumper swing out that I added an RV faucet to, and a pressurized air line coming off a ~7 psi regulator from my on board air. The 5 gal container is not a pressure vessel and it worked well for years, but lately has started leaking air from the lid. And the last couple trips I have taken into the high desert the exposed tap has frozen overnight and taken until after noon the next day to defrost enough to be used.

I am working on an upgraded system and would like any input you might have. Requirements for the new system:

• 10+ gallon capacity
• 2-3 gallons of heated water (mostly for washing dishes, tea/coffee, filling a nalgene bottle to put in the end of a sleeping bag on a cold night)
  • strongly prefer using a heat exchanger with engine coolant to heat the water, like an isotemp
• No freezing with overnight temps in the 20s (F)
• All tanks and lines must be outside the passenger compartment. My Blazer is far too small to fit any water tanks inside (cargo area is less than 3' from tailgate to rear seat, and half of that space is permanently filled with a fridge/stove/tools)

One solution seems to be a bigger, better system that is air pressurized like what I already have. I already have powerful oilless compressors, an air tank and an appropriate regulator installed in my truck that can all be reused. The diagram and notes below shows what I have in mind:

• There would be 2 tanks (10 gal and 3 gal kegs from a brewing supplier, like this). To fill the tanks, open the Fill Valves (normally closed electric solenoid valves) and pour water into a fill port in the fender. This would be beneath an access door like the gas tank filler neck. Once the tanks are full close the fill valves, sealing the system air tight.
• To use the system, open the Pressure Valve and apply regulated air pressure to the tanks. Water is forced out of the tanks through the red and purple lines to the tap on the bumper swingout.
  • Since the hot tank is heated by engine coolant (195-225F) a thermostat valve is needed to prevent scalding water from reaching the tap.
  • At 20 psi the boiling point of water is raised to 260F so there is no risk of boiling the water in the tank, but it could still be dangerously hot.
• If low overnight temperatures are expected, close the Pressure Valve and open the Fill Valves to vent the tanks to atmosphere. Open the Purge Valve to blow air back through the lines and force all the water back into the tanks. Then close the Fill Valves and open the tap to allow air pressure to blow any remaining water out of the other side of the line and out of the tap.

Total cost for this system would be $350 in kegs, $150 for cheap 1.5" stainless solenoids for the fill valves, and whatever it costs for the thermostat valve and PEX tube for water lines. I already have a ton of 3/8" air valves, tube and fittings left over from other projects that I can use, and I have copper tube to make the heat exchanger. I can do all the stainless welding to modify the kegs myself, and I can fabricate the heat exchanger myself.

To do an electric system with pumps I would still need a 10 gal tank, but it could be plastic and somewhat cheaper than a $200 keg. And I would not need the 1.5" stainless valves. But offsetting that cost I would need to buy a pump and accumulator. I think the hot water tank would still need to be metal to take the heat and pressure (I assume it would be fed from the main tank and thus pressurized by the pump, if not a second pump would be needed), and all the water plumbing and thermostat valve would be the same for either system. I don't see how it would be possible to fully drain the pump, lines and tap in an electric system every night and I don't know how I would prevent it from freezing. If I use an accumulator tank I think it might also be heavier than the air pressurized system, but using a demand pump without an accumulator would be lighter.

What do you think? Am I missing something obvious, or is air pressurized the way to go? If I did a pump and accumulator system how would you prevent the tap, lines and pump from freezing?

 

[Joe917]

Jabsco or Shurflo 12V water pump. Simple.
We had an Isotemp hwt in our truck. The first one lasted more than 20 years. The second is more than 10 years old. Great product.

 

[86scotty]

Don't do a pressurized water system.

There, I tried.

 

[NOPEC]

In my last camper build, I wanted to keep the water system very simple, lightweight and completely plug and play so as to do away with both the usual winterizing and as well, all of the fixed water lines. I used a marine Whale Brand High pressure immersion pump and two identical 5 USgal plastic water jugs. The jug below the sink contains the pump and the other is a spare which can be easily swapped out. I previously built a couple of systems using a Shurflo pump and accumulator and after using this current setup which I am really happy with, I would never go back to a pressure system. The Blue container is for my gray water. What I don't have is a hot water system, so this suggestion may not be that useful to you.

 

[grummy]

I think because of the space, its more work than a simple electric pump setup, though, You should have some interesting space under that K5 hood!

I've done pressurized and a wort plate exchanger on an insulated aluminum tank. But I had space to do it. Still, compared to my newer setup, it was just clumsy. I've downsized to a little 6x12 trailer now. I kicked ideas around just like you did all in order to not use a pump setup, but in the end, it made no sense to jump through all those hoops. I too wanted a cold tank and a 3 gal hot tank, but frankly, in your case as well, the space it takes to have that 2-3 gallon/engine heated setup is a lot more hassle than just buying an Eco-temp style propane heater for $120, IF that is really what you need.

When I am just taking my pickup ('83 Squarebody), for hot water, I take along my 4 gallon stainless pump sprayer tank, fill it, place it in the campfire or on the stove to heat it up. I have a insulated sleeve I slip over it when its hot and it stays hot for a long time. I can use it with just a kitchen sink sprayer or plumb it into a sink system if I want. I also have pressurized it with a 12v Airbrush compressor, but the old hand pump works just fine.

Nope, with your limited space, put a plastic tank under the truck. Mount it inside a 1" pink foam insulated box. One simple water line to the pump (no accumulator necessary), and out to the sink. I'm sure you can find a spot to mount a $30 pump inside. For freezing worries, I would add a small solar exchanger circulation pump in the system and turn that on if you think your going to freeze. As long as it's moving, it wont freeze.

And what will you power that with ? Put the largest Lithium battery you can get under that hood !

Not sure what your actually doing for power. I've dropped an immersion heater (120v) in that stainless sprayer tank... and plumbed it in to feed the sink with some QD connectors. But I tell you, I sure do love my little Eco-Temp style heater! If you have enough battery, you could perhaps install a 12v immersion heater and just keep it to maintain. Some guys use a 12v 300watt heater in a tank of water to use excess solar power after they're batteries are fully charged. I just do not know how much time it takes to heat 4 gallons with 300 watts or to what temp I could get it.

 

[dieselBlazer]

Don't do a pressurized water system.

There, I tried.

Lol. Fair enough

In my last camper build, I wanted to keep the water system very simple, lightweight and completely plug and play so as to do away with both the usual winterizing and as well, all of the fixed water lines. I used a marine Whale Brand High pressure immersion pump and two identical 5 USgal plastic water jugs. The jug below the sink contains the pump and the other is a spare which can be easily swapped out. I previously built a couple of systems using a Shurflo pump and accumulator and after using this current setup which I am really happy with, I would never go back to a pressure system. The Blue container is for my gray water. What I don't have is a hot water system, so this suggestion may not be that useful to you.

I do like the simplicity of that system, and I might give up the hot water for a more simple installation. With everything inside I bet it doesnt freeze often.
I dont have any space in the cargo area for water jugs unfortunately, and I prefer not to hang them on the bumper way behind the axle. Those constraints lead me to tanks under the floor with an RV style filler neck, which means I need to run a pump or another pressure solution.

I think because of the space, its more work than a simple electric pump setup, though, You should have some interesting space under that K5 hood!

I've done pressurized and a wort plate exchanger on an insulated aluminum tank. But I had space to do it. Still, compared to my newer setup, it was just clumsy. I've downsized to a little 6x12 trailer now. I kicked ideas around just like you did all in order to not use a pump setup, but in the end, it made no sense to jump through all those hoops. I too wanted a cold tank and a 3 gal hot tank, but frankly, in your case as well, the space it takes to have that 2-3 gallon/engine heated setup is a lot more hassle than just buying an Eco-temp style propane heater for $120, IF that is really what you need.

When I am just taking my pickup ('83 Squarebody), for hot water, I take along my 4 gallon stainless pump sprayer tank, fill it, place it in the campfire or on the stove to heat it up. I have a insulated sleeve I slip over it when its hot and it stays hot for a long time. I can use it with just a kitchen sink sprayer or plumb it into a sink system if I want. I also have pressurized it with a 12v Airbrush compressor, but the old hand pump works just fine.

Nope, with your limited space, put a plastic tank under the truck. Mount it inside a 1" pink foam insulated box. One simple water line to the pump (no accumulator necessary), and out to the sink. I'm sure you can find a spot to mount a $30 pump inside. For freezing worries, I would add a small solar exchanger circulation pump in the system and turn that on if you think your going to freeze. As long as it's moving, it wont freeze.

And what will you power that with ? Put the largest Lithium battery you can get under that hood !

Not sure what your actually doing for power. I've dropped an immersion heater (120v) in that stainless sprayer tank... and plumbed it in to feed the sink with some QD connectors. But I tell you, I sure do love my little Eco-Temp style heater! If you have enough battery, you could perhaps install a 12v immersion heater and just keep it to maintain. Some guys use a 12v 300watt heater in a tank of water to use excess solar power after they're batteries are fully charged. I just do not know how much time it takes to heat 4 gallons with 300 watts or to what temp I could get it.

Amazingly, I dont have much space under the hood... The truck is a military version with a 24v electrical system and 2 alternators, and I've added air conditioning, a turbocharger, and 2 large electric air compressors. The exhaust runs outside the frame now due to packaging constraints with the turbo, so I have all the area under the cargo area in front of the axle (where the exhaust and mufflers used to be) for tanks.

I have 2.5 kw of alternator output when the engine is running, but power is very limited with the engine off. I have 300w of solar on the roof connected to the starting batteries which power my fridge, Starlink and other house loads. There is no separate house battery and I had to go pretty small on the starting batteries to fit the turbo. I used to have 2 group 31 batteries with ~85 Ah capacity but now have 2x AGM batteries with closer to 55 Ah. I could add a lithium bank, but it would need to go under the floor where I am trying to put the water tanks. I think I'd rather keep electrical loads low if possible instead of add larger batteries. An immersion heater would work and I could easily power a 24v/1200W heater element while the engine is running, but that would kill the batteries in under an hour with the engine off. That would heat 3 gallons from 40F to 200F in about an hour but at the point I install a separate hot water tank I might as well heat it with engine coolant. If I'm just preventing a large well insulated tank from freezing I should have enough solar for that.

Have you had good luck with electric demand pumps and no accumulator? And is there a pump you recommend? My pressurized system delivers good flow with only ~5psi (similar to the sink in my house), and one of my friends has an electric pump that struggles to fill a water bottle in a reasonable time. Maybe his pump is cheap junk though, I'm not sure.


Driver side of the engine bay is filled up with the turbo, air cleaner and starting batteries


This was taken before the turbo, but the AC compressor and air compressors are still the same and fill most of the passenger side of the engine bay


And this is what I mean when I say space in the cab is limited. This is pretty typical of how I end up packed with camping and climbing gear for 4 people for a weekend lol

 

[grummy]

>>> Have you had good luck with electric demand pumps and no accumulator? And is there a pump you recommend?

I've just been using $30 Seaflow pumps from Amazon. They are only 1.2GPM, but any bigger, and my family would smoke through a 10 gallon tank in a few minutes. I dont have an accumulator... it just starts tickiing the minute I turn it on.

Wow, that engine bay is full ! And, by the looks of the back, I'd be pulling a trailer at this point. Either a small rig for gear only, or, the way I roll, a modified small cargo that can handle better living conditions. It sure would insulate better than any car type structure. Even a little 5x8 could pack in everything you want... plenty of solar on the roof, room for batteries, hot/cold water, gear and a double bed !

I'd be chasing down a sundowner miniGO trailer... it would make for an awesome rig behind a K5!

 

[NOPEC]

Those constraints lead me to tanks under the floor with an RV style filler neck, which means I need to run a pump or another pressure solution.

The immersion pumps are basically a lift pump. You would have no issue lifting water from an underfloor tank to your sink(or container) in the living compartment. The beauty is that the low pressure water line (Nalgene brand in my case) stays charged after initial use but once you lift the pump out of the water, the water line back drains by gravity through the pump, preventing freezing of either the line or the pump.

 

[dieselBlazer]

The immersion pumps are basically a lift pump. You would have no issue lifting water from an underfloor tank to your sink(or container) in the living compartment. The beauty is that the low pressure water line (Nalgene brand in my case) stays charged after initial use but once you lift the pump out of the water, the water line back drains by gravity through the pump, preventing freezing of either the line or the pump.

I had assumed all of the RV and camper water pumps had internal check valves. If that's not the case then something like that could definitely work. When you say lift the pump out of the water, how do you do that for a tank that is under the floor?

 

[NOPEC]

I had assumed all of the RV and camper water pumps had internal check valves. If that's not the case then something like that could definitely work. When you say lift the pump out of the water, how do you do that for a tank that is under the floor?

Boy, I'm no pump expert but I think the simple immersion types of fairly low pressure pumps that sit in water or gasoline have no check valve but instead, rely on the fact they are immersed in liquid to prevents back flow from the line. Of course, the pressure to move the liquid up is created by the rotation of the pump's impeller.

As far as building a system, you would need an access port through your floor as well as, an access means to the actual tank. Remember, if you have a sealed tank, you need a vent. I use marine style screw top deck hatches for lots of things and those might work for access. I would worry about dirt and road grime sitting on top of the tank with the system you are considering.

 

[Ozarker]

A pressurized system, oh, you'll be sorry!

That's the best I can do for ya! Good luck.....

 

[Herbie]

Two problems I see so far:

• In addition to the fill line, you'll need a vent line while filling. (And probably one-way valves on the pressure lines to ensure you don't accidentally force water or moist air back into the air system.)
• Any system that depends on you, a human, correctly anticipating weather conditions to have valves in the correct position to allow venting (or not) is doomed to you getting it wrong at least once, with whatever failures will ensue.