Yes I know that you can dry camp and/or use RV antifreeze to mitigate freezing issues, but that is not the objective here. And I'm not trying to create something that would work at sub zero F temps, my target would be around 10-15 F/-10 C. It never gets colder than that where I live or would plan to camp. I just wanted to get some thoughts on my concept prior to proceeding, in case I'm missing something, so if you're willing to take the time to read through what follows I'd appreciate it. 

Personally, I think we have to recognize the limitations of a 3 season light weight trailer and just enjoy what we have.  The anti freezing suggestions of offgrid are really cool and, provided nothing fails, would probably keep the water and drain system from freezing, but it doesn't eliminate the fact that the R value of the walls is a smidge over 5 and that's not very much to retain heat.  And, for the areas that have the heater, water heater, and refrigerator, the R value is <1; just little metal doors, open vents, and 1/8" plywood on the inside of the trailer.  That's a lot of heat loss potential.  

I don't mean to be a contrary one [well actually I do as I'm just a grumpy old man], but trying to turn an r-Pod into something it isn't, is just a hole in an RV park into which you throw money.  Every time you beef up some element, all you do is transfer the weak link in system to another component.  If you put a 6,000 axle under the frame, you still have a frame designed for loads in the range of the GVW.  You're just moving the weak link in the chain to another spot.  ....And, we haven't even talked about driving in the snow and ice with a trailer.  

For our Pod, in the world of RV's it's old and I hesitate to sink a lot of money into it except to keep it functioning well.  We're fortunate in that if we want to camp in the winter, all we have to do is cross the Sierra Nevada mountains on a nice day and go to the CA coast.  No worries about freezing there and it only takes a few minutes to winterize for the trip home and alcohol antifreeze is not costly.  

Another thing that concerns me about winter camping is driving a trailer in the snow.  I know people do it all the time, but there are a lot of accidents too.  And putting chains on the TV and Trailer, as is required at least in NV and CA is far, far too much work for my petite wife.  I don't think I could convincer her to do it.  In fact I have a hard time convincing her to go camping when it's just a little nippy outside.  

It's nice to know that the Pods have an axle that is actually stronger than the stated rating.  I've jammed a lot of stuff in the trailer before for long trips, both in the back of the truck and the trailer and have never worried about overloading, even with the water tank full.  Everything is stable and appears to be balanced with the WDH.  The Dakota seems to manage it fine, though up really steep hills, I sometimes wish I had a diesel.  It's embarrassing to get passed by a 18 wheeler.  

The closed cell foam kit will be the most expensive item. I want to add about 1 inch of insulation to the entire bottom of the trailer and the tanks. That's roughly 100 board feet and a 150 board ft kit looks like its about $400 on Amazon. 

I used to live in Santa Cruz and never used the air conditioning or winterized the class A RV I had back then. If it was summer and hot in the valley we either camped on the coast or above 5000 ft in the Sierras. In the winter we stayed on the coast. 

Where I live here it rarely freezes, but it does occasionally. Just a bit colder than Santa Cruz, enough that you need to deal with freezing but not enough that I feel like I want to fully winterize. But to go somewhere else in the winter here, say to Florida, we would be exposed to significantly more cold temps inland while enroute. 

Yeah I know about snow in the Sierras. Snow is different here in the east. Part of life. No one uses chains. Unheard of. People do run winter tires if they're further north or in the mountains. Use lots of sand and salt. If there is a heavy snowfall you just don't travel till the roads get plowed and treated unless you absolutely have to.  Really heavy snow things shut down. So, I'm not planning on any travel with the rPod in severe conditions. 

Don't count on your particular axle being higher rated, FR uses both Dexter and Lippert axles and probably more than one version of each. If you want to know for sure, get the model number (Lippert calls it the variant number, mine is 165646) off the axle label and call the axle manufacturer.  

You need to ask the question carefully though, if I had asked Lippert what the axle rating was on mine they would have correctly said 3500 lbs. But when I asked them what the next higher rated axle was, could I buy that, and what the differences were they said it was only the label but they'd be happy to sell me one. Needless to say, I didn't place an order.

Altho I'd like to have a 4-season camper too, I agree with all of the above. 

If you have camped in the winter, enough said. If you haven't, another factor is condensation and it's mitigation. Condensation turns into ice in odd places which then expands and bad things happen, and then there is also mould formation from the condensation, perhaps not a problem until the next spring, but ...

I read through your links and found them very useful. I have a couple of questions.

Looks like the solenoid part of your system is very similar to what I plan to do, other than I'm thinking of using a thermostat rather than a timer and will be dumping the water back into the fresh water tank. How did the timer work out for you, did you do any testing to determine your cycle times? Did you consider a thermostat and if so, what made you decide on the timer approach? Also, do you recall what solenoid you used?

I'm planning to use the solenoid only to heat the fresh water tank and the pressure pump suction line (because feedwater would return to the system through that line whenever the solenoid was energized). 

For the hot and cold water lines as well as the gray and black tanks I'm planning a circulator pump, just connected between the hot and cold lines at the water heater. This is where the circulators are usually placed in residential instant hot water systems. The circ pump is left running in those (its tiny) and generally a temp sensitive wax valve is placed across the hot and cold lines at the farthest point in each plumbing loop. This keeps both hot and cold lines warm. I basically want to substitute the tank drain heat exchangers I plan to make for the wax valves and turn the pump on and off via a thermostat(s) to save energy rather than just leave it running. 

Looking at the way the rPod's fresh water plumbing is laid out relative to your Camplite one benefit of the rPod is that all the hot and cold feed lines are inside the camper except for the two sets of low point drains. If I tee off the hot and return to the I think that should keep all the fresh water plumbing warm. Do you agree?  My biggest concern was the low point drains themselves which would have to stick out of the insulation a little. It sounds like you had the same potential concern but never had a freezing problem at those points with your system?

Thanks again!

Yes, dealing with snow in the west is different from the east.  We lived in northern New Jersey for several years and, except after a fresh snow fall when everything was beautiful white, snow there isn't very pleasant.  And yes, people drive without chains, indeed in some places they're forbidden, but there are a heck of a lot of ice caused crashes too.  Speaking of snow removal, how do you plan on rinsing the salts they use on the roads if you're out an around after after a snow fall?  That stuff is so insidious it eats away at everything it touches.  

As for my axle, I don't think that we've ever come close to the GVW, even at our heaviest.  Since I've taken stuff out of the trailer, such as tv and upper bunk and we have a minimalist approach to our trailer camping, it's something that I'm not too worried about.  Water is is the biggest issue for us, and when we travel, we put a lot of it forward in the bed of the truck in jugs in milk crates.  I guess that is one advantage of having a pickup truck as a TV, you can kind of spread the weight around.  Some day, when I'm feeling really frisky, I'll call FR and ask them what axle they put in the trailer.  They've been real helpful so far.

Yep, idiots drive off the roads everywhere, they don't need an excuse. Especially common after the first major winter storm of the season, seems like they forget that they no longer have traction. Snow in the cities is dirty nasty stuff. Nice clean snow in the mountains, either in the west or east, is beautiful. 

Get the road salt off? He he, least of my worries.  I live on the Outer Banks. Salt water, salt spray, salty sand everywhere, all the time. I get under my vehicles, flush them with fresh water, dry, spray WD40 everywhere. WD stand for water displacement, if you can fill up all the little gaps and cracks with something else salt water can't get in there. It helps, but stuff still rusts. 

I also use Fluid Film, a lanolin based water displacement material. Thicker, so stays on surfaces longer and fills bigger gaps. Good stuff. Gotta flush and recoat a couple times a year though. Basically I just try to do the best I can and avoid the salt as much as possible. 

The heat exchange transfer rates are less well understood, those probably are actually about a factor of 2. Those govern how long the circ pump is on. So I plan to design for worst case and if the transfers are more efficient, great. The power requirement for the circ pump is so low that it really doesn't matter much. 

Actually it turns out after some more research that ciculators use less power and are more reliable than solenoid valves. The reason looks like it is because the circulators aren't trying to fight against water pressure, they just pump a small amount of water at very low head pressure from the hot to the cold side of the water heater. I would prefer to use a circulator for everything except that I can't figure out how to transfer heat to the fresh water tank that way, without putting more holes in the tank. As you say polyethylene isn't the best material to try to adhere stuff to.  

The other reason I like the idea of using a circulator in the rPod 179 is because the hot and cold low point lines are adjacent and at the far ends of the plumbing run so by recirculating between the hot and cold lines you are guaranteed to heat all the pressure lines. 

You could adhere copper tubing to the waste tank bottoms but it would require much more tubing than a immersion heat exchanger, and I would be concerned about how to heat the drain lines that way. The drain lines and gate valves are going to be more prone to freezing than the tanks themselves.  I don't plan on inserting anything into the waste tanks themselves, the Cu heat exchange tubing would be inside the drain lines, so no new holes in the tanks. I've done horizontal tube immersion heat exchangers before and as you might expect, copper ones work quite well. I used to heat my hot tub that way from my gas water heater, silent and almost zero electrical requirements. 

I did take a look at flow rates though the heat exchangers vs just running hot water into the tank and the duty cycle I get for running hot water into the tank is well under 1%, so it sounds like its about where you set your timer. The duty cycle for the heat exchangers/circulator is between 25 and 50%., so they are not a good match.  So I can't simply dump water from the heat exchangers back into the fresh water tank. 

Maybe I should just go ahead and install a couple of blind bulkhead fittings in the fresh water tank install a heat exchanger through it, and dispense with the solenoid valve. I could route one of the lines from that exchanger next to the pressure pump suction line to heat that. Then I could probably just leave the circulator on all the time when its below freezing, that would really simplify things. It would still only use well under 20Ah per day, not a big deal. 

Although a lot of work, this thread is an interesting concept and would be a good solution for extreme temps.  We just went up to Taos Ski Valley from Dallas for the long weekend to go skiing in our 2016 176 Rpod.  I wanted to have access to water and shower so I put heating pads on the three tanks, 12V self-regulating heat tape on the exposed fresh water line from tank and wrapped in the pipe insulation with aluminum tape going on before and after.  I also put the heat tape around the grey water valve.  Last weekend it was subzero, around -6 at night in the ski valley but was warming up to near freezing during the day. The only trouble we had was that in the morning each day the hot and cold water to the shower as well as the toilet water was frozen.  We left the electric heater on high all day (took a generator with us) and when we got back the lines were no longer frozen.  The lines are not exposed but run through the floor.  So I suspect that just being adjacent the bottom layer of the floor was enough to freeze the lines at these temps.  Not sure what can be done about that except maybe putting insulation under the Rpod or adding a skirt?  Anybody else have this issue and figure out a simple solution?  The electric heater would keep up with keeping the RV warm inside, even too warm.  We didn't add any extra insulation anywhere.

If you skip doing my proposed heating system for the waste tanks and just use some extra antifreeze in them as CharlieM suggests then that would save most of the effort. I think that some type of insulation on the fresh water tank would probably still be required in the temps you're experiencing to keep propane use down but you could try it first without it.  I'd also be tempted to just remove the low point drains, they're really only there to reduce antifreeze use and create an unnecessary freeze sensitive spot. You should add interior cutoffs for the outside shower or you'll probably be replacing that come spring. 

offgrid

i think the recirculating method is the best solution, just a little above my pay grade of savvy.  i am trying to see if i think i can do it.  i get the pump and the recirculation concept, but the solenoid and relay stuff throws me for a loop.  need to do some homework.

offgrid and/or charlie,

a few questions on this: 

1.  this will require a tap into fresh water tank for return correct? what is the best way to do that?

2. concept question: what about the water lines at a sink for instance? no water actually circulates say the last foot unless you open the sink valves.  Does the water actually circulate enough within the line to accomplish the necessary heat distribution ?  or is this moot since these areas are in heated living areas?  for instance in Charlies schematic of the water lines, the hot and cold to the shower?

3. Is the manual valve on the solenoid pump just for pressure and flow limiting ?

 I used one of the little Chinese thermostats in another project to provide a precise temp control for the water heater. There is a thread on it on the forum.  It runs on 12Vdc which is available at the water heater controls and should be able to run a 12V solenoid valve just fine. The temp probe for the thermostat can go on the lowest place in the system (bottom of the fresh water tank or on the bottom of the pump feed line at the tank).  You can get 2 thermostats for $8 on Amazon and have a second one to adjust the water heater temp. 

https://www.amazon.com/HiLetgo-Temperature-Controller-Thermostat-One-channel/dp/B07CH7W3XP/ref=pd_sim_328_2/145-8709395-3663044?_encoding=UTF8&pd_rd_i=B07CH7W3XP&pd_rd_r=c892e5d4-1e83-11e9-8739-9941e184f583&pd_rd_w=85MgR&pd_rd_wg=JxkeJ&pf_rd_p=18bb0b78-4200-49b9-ac91-f141d61a1780&pf_rd_r=WXCJRBAXMZMVQD4HQMAY&psc=1&refRID=WXCJRBAXMZMVQD4HQMAY

A solenoid valve like this should work OK. You'll need some plumbing parts to connect it up. 

https://www.amazon.com/SNS-2W025-08-Electric-Solenoid-Normally/dp/B0794XJGBF/ref=sr_1_5?crid=1SJGTGMTXP1KO&keywords=12v+solenoid+valve&qid=1548188854&sprefix=12v+solen%2Cfashion%2C261&sr=8-5. 

CharlieM did this mod on another brand of trailer and has a link to it on this thread. 

I would suggest doing away with all the low point drains and sealing the holes with closed cell foam insulation. If you want to winterize with antifreeze just open the valve at the far end and run the antifreeze through the whole system that way. You'll want cutoff valves for your outside shower too. 

am i on the right track ?

texman, you have the operating theory correct, Just one clarification,  the thermostat on the water heater operates independently of the one on the recirc system. The water heater will turn on when its thermostat calls for heat, which might or might not be when the recirc system is operating. 

The purpose for adding the new thermostat on the water heater is only to be able to set the water temp lower than the 130 deg non adjustable setting of the standard thermostat. By setting the temp down around 102-110 degrees (whatever feels comfortable to you) you don't ever get scalded, you don't need to fiddle with adjusting the water temp, and you waste less water. So, you won't need to change the recirc system back to its normal hot and cold setup in order to use the water in the winter. 

In my case, when I do the recirc mod I don't think I'll ever change it back to allow separate hot and cold line function, even in summer. As I don't drink or rinse food with the trailer tap water (I don't trust the water in the tank so I use bottled water for those purposes and for brushing my teeth),  I really have no need for the cold water function. 

I think you shouldn't need to set the recirc thermostat setpoint anywhere near as high as 60 degrees. If its temp sensor is located at the coldest low point of the system its probably OK to set it more like 35-40 degrees. Some testing will probably be required to dial that in. The temp sensors on the little thermostat boards are thermistors so if the wires to them are too short you can cut them and splice in longer wires without causing a problem.  The boards are supposed to have a temp calibration adjustment but the one I bought didn't, so I had to use a separate thermometer to set up mine the first time. Just immerse both the temp probe and a known good thermometer in a glass of water and record the temp difference for later use. 

Re your earlier question about whether the water recirc freeze protection will work for the risers up to the trailer appliances from the water lines in the floor, I would assume that it doesn't until proven otherwise. So, there should be a way for maintaining the interior of the trailer above freezing at all times unless you winterize. I'd also leave the cabinet doors open a bit under the sink and by the new cutoffs you would install for the outside shower. 

That being said, since those appliance lines are risers, it is very likely that the water in them will warm somewhat just from natural convection from the heated lines in the floor. You'd have to experiment a bit and maybe take some temp measurements to determine how warm the interior of the trailer needs to be to keep them from freezing. It might be a pretty low temp.

i am thinking of getting this valve instead of the solenoid.

https://www.amazon.com/gp/product/B06WWPZWGZ/ref=ox_sc_act_title_1?smid=A20QEF2LEKCK8G&psc=1

Reasons: 

1. I am having trouble finding 1/4" npt to 1/2" pex, so 1/2" npt valve is easier to source parts to tap into my 1/2" pex.  i was planning to use shark bit pex fittings since i dont have the clamp tool. 1/2 pex to 1/2" npt is readily available at lowes.

2. This is motorized ball valve instead of a solenoid with auto return to close when no power.  So it should work with the thermostats that i have, i think.  So it will still use some power while open (30ma) since it is auto return, but much less than a solenoid (1.25A if my math is correct in converting 15va at 12v.) and shouldn't have the heating problem that a solenoid can have.

please let me know if you think this will work.

i am planning to use the shark bite fittings since i dont have any pex tools.  they should work well in the tight areas i think. 

my 182g has two low drain points and the rear kitchen sink too.  i plan to put valves and join the low point drains and move them inside the pod walls if possible.  not sure that will work out if the low point drains will be inaccesible one moved inside the pod. need to do some investigating.

i am also thinking i will add a pressure regulator to limit the amount of water flowing back into the fresh water tank via the overflow line.  hopefully that will limit the flow enough to allow the water to drain back into the tank instead of blow out the overflow.

I am thinking of doing this modification, mostly to reduce water use by pre-heating the water going to the kitchen sink and the shower. The valve in the link is brass, and the listing states that it is not for use with drinking water due to lead content. I have been looking at a stainless steel version, but can't find it in a 1/2" model. I did find this 1/4" model:

https://www.amazon.com/Wire-Auto-Return-Stainless-Motorized/dp/B07X8FQ8ZK/ - https://www.amazon.com/Wire-Auto-Return-Stainless-Motorized/dp/B07X8FQ8ZK/

With a couple of adapters, would this work? I would think that a small water flow through a 1/4" valve would be adequate for the tasks of making sure hot water is available immediately as well as to help with freeze prevention in overnight breeze situations. Given the smaller diameter, it also should be less likely to be too much for the overflow pipe to handle on the return side. What do you think?

https://www.amazon.com/gp/product/B06WWPZWGZ/ref=ox_sc_act_title_1?smid=A20QEF2LEKCK8G&psc=1 - https://www.amazon.com/gp/product/B06WWPZWGZ/ref=ox_sc_act_title_1?smid=A20QEF2LEKCK8G&psc=1

which is cheaper, the right size and is a 3 wire device, and run it from the little W1209 thermostat card via a spdt (single pole double throw) relay, like this:

https://www.amazon.com/Absolute-RLS125-12-VCD-Automotive-Relay/dp/B0002KR9GG?ref_=fsclp_pl_dp_1 - https://www.amazon.com/Absolute-RLS125-12-VCD-Automotive-Relay/dp/B0002KR9GG?ref_=fsclp_pl_dp_1

It would have the added advantage of better isolation of the W1208 thermostat. IIRC, Texman had a noise issue with a couple of the ones he got originally and had to get a second set. His second set were the same as the ones I got for my water heater temp adjustment which worked OK. 

1" seems a bit large. What about 3/4" stainless steel?

https://www.amazon.com/gp/product/B06XW8MSTX/ - https://www.amazon.com/gp/product/B06XW8MSTX/

Also, the link was for a 2-wire auto-return valve. I was not thinking of running it with a thermostat, but either manually or with a timer. The primary use will be the instant hot water. I don't recall the issues Texman had. I'll have to look for that post.

Or, get one of these instead of a manual on/off switch. Just push the button once and forget. Not sure if 10 seconds is enough or not, might need a different potentiometer. 

https://www.amazon.com/Akozon-Module-Adjustable-Timing-1-10sec/dp/B07H7J91RM/ref=sr_1_20?dchild=1&keywords=12v+time+delay+switch&qid=1588102892&sr=8-20 - https://www.amazon.com/Akozon-Module-Adjustable-Timing-1-10sec/dp/B07H7J91RM/ref=sr_1_20?dchild=1&keywords=12v+time+delay+switch&qid=1588102892&sr=8-20

How many valves did you install? Did you do a valve by the kitchen sink and another by the shower since (at least on the 179) one valve would not be able to serve both areas.

Have the motorized valves worked out better than solenoid valves would have? Are they reliable?

two valves.  one at water heater and one at the rear kitchen to allow a complete mix of hot/cold.  so far the motorized valves are great.  i like them better because they only power when switching and minimal power use to stay open and none when closed. 

so in my 182g, the cold line from main to sink and main to shower would get minimal recirculation, but are enclosed and in heated spaces.  i figured the rear kitchen water supply was vulnerable to freezing since it is not in a heated part of trailer and adjacent to a semi exterior wall. 

from Feb 6th 2019 post