Solution to frozen water lines?

[grinnelljd]

I have a Sportsmobile that is built on a 2018 4x4 2500 144"wb, high top Sprinter. The floor plan is virtually identical to their standard RB110S floor plan. That is: shower/bath behind driver's seat, closet behind the shower/bath, galley on passenger side, and a dinette/bed at the rear of the van.

The fresh water tank is inside, near the rear of the van under the passenger side dinette seat. The batteries and inverter are similarly located under the driver's side dinette. Most of my Rixen's Comfort Hot system is installed in a cubby at the bottom of the closet between the dinette and the shower/bath. The Espar D5 diesel furnace is mounted to the outside frame rail, under the van, directly under the closet.

My problem is that occasionally, when it is very cold outside, the water line running within the floor, from left to right side, just forward of my wheel wells becomes frozen, even if I run the heat on the Comfort Hot system at a high setting like 80-85F. To be fair, I've monitored the temps inside the dinette enclosures and they typically are much colder than the temps in the rest of the van. With the thermostat set for 80F, it is not unusual to see temps of 40F in the rear of the van under the dinette seat. So I'm not shocked that the water line running within the floor is freezing; water lines on the outside walls of regular houses can similarly freeze.

As I see it I have a few different ways to fix this issue.

1. I could install a 12volt self-regulating heating line in the floor channel containing the water line. During cold weather I could turn this line on and it would heat up to about 100F, preventing the line from freezing. I've looked though, and it appears that the floor channel is currently just wide enough to house the water line and not wide enough for me to snake this heating line through as well. I'd need to cut my nice loncoin floor surface in order to widen the existing floor channel or add a second parallel channel in the floor near the water line.

2. I could add ventilation to both the dinette seat enclosures to force heated air into these areas which tend to stay cold. I'm just not sure if this will be enough to keep the water line which runs within the floor from freezing. A part of this water line runs just under the floor in the center aisle, which would be warmer, so my guess is that the line is freezing somewhere under either of the dinette seat enclosures.

3. At some point, I'd love to extend my Comfort Hot hydronic lines to loop around my two 10 gallon grey water tanks under my van and then insulate these tanks. This would give me something like the insulated and heated tanks found in the Winnebago Revel. During this process I could also run a section of the hydronic line along the underside of the metal van floor directly beneath this water line in the floor. An insulated cover would serve to keep the heat concentrated along this section of the floor and should keep the water line from freezing. This is, by far, the more expensive option, but would give me a much more Winter capable vehicle.

At the moment, I'm leaning towards option 2 as I can easily wire a set of USB ports under each dinette seat into which I can plug quiet USB vent fans used for ventilating media cabinets. These fans can be configured to draw warmer air from the aisle of the van into the colder areas under the dinette seats.

Has anyone addressed similar issues and what was your solution?

[carringb]

I had the same problem with my trailer. I ended up using a can of foam to bond foam-board to the bottom of the floor, where it wasn't enclosed and was causing the freeze-ups. In your case, I suspect you'd still want to vent the dinettes. It might not be 100% frost-proof, but probably much better and also inexpensive.

[gahamby]

Is there a way to keep the water circulating through the cross vehicle line when temps fall to freezing?

[carringb]

Originally Posted by gahamby

Is there a way to keep the water circulating through the cross vehicle line when temps fall to freezing?

Yes, but you would need a hot-water return line to the fresh-tank. This is usually very straightforward in a trailer, but if sounds like this van would require a 2nd pipe chase in the floor, to run another line back across. The return line would need a solenoid, and a controller or timer to periodically run hot water back to the fresh tank. This not only keeps the lines from freeing, but keeps the fresh tank protected as well.

[grinnelljd]

Originally Posted by gahamby

Is there a way to keep the water circulating through the cross vehicle line when temps fall to freezing?

Not the way the plumbing lines are currently.

The best I can do is to slightly open the cold water line in the shower and allow it to slowly drip overnight, when the temps are the coldest, to keep a tiny flow of water in the line under the floor. However, even a small drip will use gallons of water supply so that isn't a great solution.

To continually circulate the water in the underfloor cold water line, I would need to add a water return line back to the water tank. Also, the pump would have to run to maintain flow and RV pumps are not made for constant duty like that. Besides, if I were going to open up my floor to add a return line, I'd take the easier route and open up the floor to add a small 12volt self regulating heater cable to keep the original cold water line from freezing.

[grinnelljd]

So, I think I may have remedied my freezing water line issue.

I added a USB powered vent fan to the face of the dinette seat cabinet. This fan draws air from the heated area of the van into the area under the dinette seat. Because of the cabinet type enclosure of this dinette seat, the air undertake seat would stay very cold compared to the inside of the van. This would sometime lead to the water line, which travels under the floor from the passenger side of the van to the driver's side, to freeze up.

Now with the newly installed vent fan in place, the air under the dinette seat is much closer to the temperature of the air in the living area of the van. You can see that with an inside van temp of 65F, the area under the dinette seat (measured using the outside temp probe) was at 57F. Much better. This should help to mitigate the freezing issue.

[Twoxentrix]

I like the concept! Hope it resolves your issue - would be great if you provide a follow-up after you've had a chance to allow your install to be "tested".

[grinnelljd]

Originally Posted by Twoxentrix

I like the concept! Hope it resolves your issue - would be great if you provide a follow-up after you've had a chance to allow your install to be "tested".

Thanks. I should the opportunity to give it a proper test soon as I've already equipped my van with snow tires so I'm looking forward to heading up the Adirondacks or Vermont for some winter van camping.

My short test, here at home, started with the interior of the van at 40F and the area under the dinette seat at 33F. I heated up the van to 65F and the area under the seat didn't rise much, holding around 37F. Then I turned on the vent fan which pulled warm air under the dinette seat. It didn't take long before it hit 57F which made for a good first test of the concept.

[allenl]

I'm also super interested in hearing some long term results. I've got similar issues and I like the vent fan idea instead of running 12v heat traces.

Thanks for the write-up!