how to design a water system that is operational below freezing

[ramblinChet]

My question is how to design a water system that is operational below freezing?

It seems as if we have two different parties to consider - those who will leave heat on all night and those who will not. There also seems to be two primary areas to consider. Area one would be the water tank itself while area two would include all the water lines, valves, pump, fittings, etc.

Maybe a simple solution for area two (water lines, pump, etc.) would be to have the ability to drain or pump the entire system back into area one (water tank) so now we are only fighting one battle. I am not familiar with plumbing so please excuse my suggestions but maybe this is a simple as having some sort of valve at the lowest point just above the tank that will permit the system to vent and drain all the water back into the main tank? Or maybe a valve that would prevent more water from being picked up from the main tank and now use the pump to pump all of the water back into the tank through a purge line?

Provided we are successful with draining all of the water back into the main tank now we no longer are worried about the pump, water lines, fittings, etc. since they are filled with air. So let's look at the most energy efficient way to prevent the main tank from freezing. We know that water will not freeze if it is moving so maybe some type of aeration system? Farmers use windmill driven aerators to keep ponds from freezing. The marine industry uses bubbles along the hulls of ships to keep that area from freezing and crushing the steel hull. If I have an air system onboard already with a five gallon tank at 150 PSI maybe I could have an aeration system plumbed into my main tank and use a slow release of bubbles to prevent the tank from freezing?

Not sure how many hours a system like that would last or how many bubbles are actually required for a given volume of water or maybe surface area is the key metric? I have no doubt that this area has been researched and many experiments have been performed so the information is out there. Maybe even a very small low draw DC powered water pump inside the main tank just to keep the water moving - like a fountain spraying up inside the tank itself?

My goal is to build a water system that can be used during freezing conditions when needed. Once I am done using it the system can be placed back into a hibernation mode where it consolidates all the fluid and keeps it from freezing. I spend much time in freezing conditions and I would like to design and build a water system that can be used below freezing temperatures.

BTW - I know many take external and internal temperatures but is anyone actually taking the temperature of the water inside the tank? That is critical information to have. Maybe a trigger that when the water temperature drops below 35 degree Fahrenheit the system becomes operational.

 

[stevo_pct]

I've been thinking about this too. My goal is to have no issues in the shoulder seasons when nights may dip below freezing but days are above freezing. I'm not looking for a solution that would be fully 4-season.

I've had similar thoughts about installing a drain valve at the lowest point near the tank. That would allow me to drain the most vulnerable parts of the system (the pump and the lines). I've also been thinking of something along the lines of heat tape.

As far as the tank goes, that probably wouldn't freeze solid if temps were just dipping into the 20s overnight, and even if it did, I'm not sure it would be a problem as long as the tank wasn't full.

 

[CFMGarage]

How much water are you planning in the main tank?

What kind of noise would an aeration system make? Would you hear the system bubbling and burping the air?

Simplicity may be insulating the tank and using a heating element external. Trigger the system to keep the tank above freezing, but I would be interested in knowing the energy usage for those elements.

*Please note that I found this link from a simple google search and I don't have an opinion on this product, just using it as an example to try and gauge the energy usage:

Rv Tank | Ultraheat | Indiana

UltraHeat is a leading supplier of RV tank heaters, grey & black tank heaters, RV tank heater pads, RV pipe heaters, and gate valve heaters for many industries.

www.ultraheat.com

This link says 4.1 amps at 13.5v for the small pad. I would hope you could apply insulation over top of this.

 

[Buddha.]

I typically winterize a camper by hooking my air line, at 40-50psi to the outside city water hookup. Then I go around the camper opening the facets, toilet, shower etc. Then I use the water pump to pump RV antifreeze through the system.
Plenty of people skip the antifreeze step. I’m not sure how you get the water out of the pump though with just air. There’s a check valve in the water pump that doesn’t allow anything back into the tank.

Maybe you could T in a air inlet between water tank and pump that would allow you to blow out the pump with the plumbing.
Possibly you could use the same T to blow air back into the tank foryour anti freezing idea. Make sure your tank vent is operating though or you may start inflating it.

 

[DiploStrat]

Operational below freezing? No problem, Wesbasto, Espar, and probably Truma make lots of systems that will heat your water and your camper. You DO have to make sure that all of your lines, pumps, etc. are inside the heated camper.

Non-operational, i.e. storage is actually harder. Here you have to drain completely, and/or use anti-freeze, and/or run heat. As my truck has a sump and no real low point drain, I use an electric oil filled radiator and shore power to keep things above freezing. (45F is the typically quoted temperature to avoid cold break throughs.)

 

[Alloy]

Water (PEX) lines/filter/pumps/heaters will not drain. The water has to be removed. People either use RV antifreeze or blow the system out with air.

Air is the fastest for start up/shut down in freezing temperatures.

Traps for the sink/shower need antifreeze/windshield fluid or can be drained if traps with a "clean out" is used and there are "waterless traps".

First issue using air to prevent freezing is contaminates. Second issue is power consumption.

DC and AC heating pad are available but once again power consumption is the issue. Solar power is lowest when the demand is greatest.

Heat from the engine/furnace/boiler is common.

Many tanks that do not drain 100%. These tanks end up with a pink/orange slime growing inside.

Bad stuff will grow inside/through filters that are not used.

Some systems filter the water going into the tank. Other system filter the water coming out of the tank.

Some people use chemicals to sanitize water and others don't.

Type of wall construction dictates how close fixtures and water (PEX) lines can be to the outside walls.

Coldest I've used my system is -5F (-20C).

 

[dstefan]

I thought I wanted a pump system when I built out my camper, but as an iterim we just went with an easy gravity feed system. After a year with it, I‘ve abandoned the pump idea. I get that many with FWCs, etc already have a pump, but not having that initially, I can’t see adding it now, both in terms of freezing, space, and complexity.

I drilled a vent hole in top of the Scepter with a SS 1/4-20 bolt as stopper. Used Scepter's flexible spigot with about 4’ of potable water 1/2” line spliced in to extend it and put it on the 8020 riser for flow. I can leave it set up when off road with no problems - doesnt budge. Carry another Scepter in back corner w/ room for a 3rd if need be. Easy to fill and uncomplicated. Can easily move it to the bed platform if we need to stay inside to cook. Has to get really cold to freeze. YMMV!

 

[billiebob]

Best is to keep the system within the heated envelope of the camper. No tanks or lines below the floor. Sewer and traps included

Insulation only slows the loss of heat. The colder it is outside the faster the water freezes and the eventually even 5 below C will freeze the best insulated lines, tank, fittings. Most winterized RVs just add a mess of spray foam. Traps are always exposed even insulated. Badly insulated homes and mobile homes without basements solve the problem by leaving a tap or two open 24/7.... not an option in an RV.

Question is once you build everything inside the heated envelope will you keep the cabin above freezing 24/7. There is no economical way to have indoor plumbing at 20 below even when it is all inside the building envelope. Biggest issue with even insulated tanks and lines under the chassis is the blast freezer effect of driving at 20 below.

Most economical solution. Bottled water. Boil water on the stove for abolutions. dump it in a snowdrift..... Black water? Dry toilet, bag it and freeze it.

 

[Trestle]

Since you're talking a camper that is isolated from the cab of the truck. Here are the three most common ways I see it done.

Option A: This assumes all lines/tanks/etc. are inside the camper's conditioned space.

Camper parked at home between use - Electric space heater with thermostat inside camper, plugged in to home. Not a bad idea to leave cabinet doors open to circulate heat, or set the space heater's thermostat higher to compensate for cabinet door isolation.

Camper while driving in cold weather - run furnace (wasteful) or add in low draw 12v tank and line heater and run from house batteries which are being charged from vehicles alternator via B2B or other charge system.

On site not driving - cabin heat.
_____

Option B: very simple system with submersible pump dropped into septer water cans. Bring fresh/gray color coded 5 gallon water cans. You can do blue for fresh, and tan for gray water. A lot of van lifers do this as a low buck system. Fit one fresh and one gray 5 gal water can under sink compartment. Pull from fresh can with submersible 12 on demand pump. (you could look at one of those fancy rechargeable Dometic units for $100), drain into gray water can. Swap fresh out as needed, dump gray as needed.

At home - water in heated space in home base

Driving - water in passenger cabin

On site not driving - cabin heat.

____

Option C: Hydronic heat system in camper tied into vehicles cooling system. Also probably a camper setup that is fully plumbed with all tanks/lines in the conditioned space.

Camper parked at home between use - Electric space heater with thermostat inside camper, plugged in to home.

Driving and on site when not driving - hydronic heating system.

 

[billiebob]

Once you involve plumbing, pressure, drains and traps..... even the most anal person will eventually miss and freeze something. Option B ^^^ is the simplest most fool proof system....

ps those bubbling air systems for marinas only work to like -5C.... any colder and they can't keep up. On a tank they only keep the middle of the tank from freezing, ice still forms on the inside tank surface. Unless everything is inside the heated envelope, the blast freezer effect on the highway will freeze anything.

 

[FAW3]

Trestle's response lays it out very well. My version of "option B":

Over a span of several types of camping vehicles and winter misadventures (van, pop-up trailer, trailer, motorhome, truck camper) in which they all had a plastic water tank & 12 volt pump water systems I tried various approaches in freezing weather. The hard reality was that the living space which encompassed the water system elements had to remain heated at all times. Grey water and grey water tanks were another problem area to deal with.

I found the best "at or below freezing weather water system" was to keep the primary water system winterized/empty and use a simplified alternate system. I liked using a portable water container (like a Reliance spigot water jug) of comfortable lifting size (2.5 gallon?) that would fit on a shelf or rack and use with the built-in spigot. Mounted over a dishpan or bucket. Water is used, heated on a stove as needed, and grey water is tossed outside. You refill the spigot jug with a reserve jug or can of 5 gallons. You keep the water jugs in the heated area you're in - either the camper or the vehicle cab. When driving the spigot jug and any reserve is moved to the heated vehicle cab. You surround the jugs with a blanket or sleeping bag when stored (including the bottom on the floor).