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Old 10-10-2020, 10:25 PM   #1
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How to Keep Water Tanks From Freezing

Iím getting ready to do some plumbing in my bus. I want to get a shower going in a big hurry. I am planning to use a light duty tankless water heater. There are two things Iím concerned about.

The first is having my freshwater get too cold for the tankless heater to heat up to a reasonable temperature. I understand they are only able to raise the water by a certain number of degrees. So if you want hot water you need to have luke warm water to start with. If my water is at 40į and my heater can only raise it By 50į, I will end up with 90į hot water. This doesnít seem hot enough unless I was to use it exclusively without mixing any cold water into it, and that seems like it would put too much demand on the heater.. Or maybe I just need to think in terms of using a lot less water than I would at home.

My second thought is about keeping the tanks from freezing. I imagine you could have some kind of heating element, but I am also thinking that in Wisconsin winters the uninsulated Storage space below the floor of my bus is it gonna be getting pretty darn cold and so it would take a lot of energy to keep the tank from freezing. Insulation would help, and a lot of insulation would help a lot. What kind of solutions are commonly used?

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Old 10-13-2020, 02:22 PM   #2
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On my future bus conversion (if I ever do another one), it'll have heating mats under the water tanks like this (https://www.amazon.com/12V-Flexible-.../dp/B074SXKPZL). You don't need much, just enough to keep the water above 32 degrees. As it stands for me, I don't travel where it gets below freezing.
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Old 10-13-2020, 03:12 PM   #3
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Quote:
Originally Posted by wrenchtech View Post
Iím getting ready to do some plumbing in my bus. I want to get a shower going in a big hurry. I am planning to use a light duty tankless water heater. There are two things Iím concerned about.

The first is having my freshwater get too cold for the tankless heater to heat up to a reasonable temperature. I understand they are only able to raise the water by a certain number of degrees. So if you want hot water you need to have luke warm water to start with. If my water is at 40į and my heater can only raise it By 50į, I will end up with 90į hot water. This doesnít seem hot enough unless I was to use it exclusively without mixing any cold water into it, and that seems like it would put too much demand on the heater.. Or maybe I just need to think in terms of using a lot less water than I would at home.

My second thought is about keeping the tanks from freezing. I imagine you could have some kind of heating element, but I am also thinking that in Wisconsin winters the uninsulated Storage space below the floor of my bus is it gonna be getting pretty darn cold and so it would take a lot of energy to keep the tank from freezing. Insulation would help, and a lot of insulation would help a lot. What kind of solutions are commonly used?

in regards to the water heater the tankless are flow based.. so the amount of rise is listed at a certain flow.. it may be that your arent using water at a high enough flow rate to have such a low rise.. the spec sheet should have a flow and rise table.. if the main reason for needing hot water is a shower, where warm water could do for hand / clothes washing you can add an electric shower head in so the 80-90 degree water from the tankless gets heated further by the shower head..



some tankless water heaters have the ability to install an external "DHW loop" essentially its a small closed loop of water that it maintains at a certain temperature.. you could run a loop pipe through your fresh water tank which would warm it up and keep it from freezing (just a thought)
-Christopher
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Old 10-13-2020, 03:42 PM   #4
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Now that's a neat idea....
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Old 10-27-2020, 10:26 PM   #5
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Keeping tanks and lines from freezing

I'm thinking through this process right now, as I get close to mounting our fresh and grey water tanks underneath the bus and setting up for plumbing (though we're a long way from hooking up water).

We bought a Dickinson Newport diesel heater and it offers the ability to add a single loop coil inside the heater to heat water. With that in mind, I am planning to create a radiant base for our water tanks, since they will be underneath the bus and not in the living space. When it's cold enough to want the heater running, we'll also have water flowing through a grid of pex on the bottom of the insulated box that will surround the tanks mounted in the basement.

That is an option worth considering. If you have a wood burning stove, it might also be possible to rig a coil and pump to drive hot water through a system designed to keep your tanks warm.

The next things I want to consider is how to keep the water lines that are underneath the bus from freezing and how to make sure we have water that is hot enough to enjoy taking a shower on a chilly day. Given that on demand water heaters can only raise a temperature so much, I am considering how I might be able to have an auxiliary tank in the living space that maintains 5-10 gallons of water at room temperature. I'm sure there are complex solutions to this one, but I also hope there are more elegant solutions to be discovered.
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Old 10-28-2020, 12:09 AM   #6
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Originally Posted by CoffeeGuy View Post
The next things I want to consider is how to keep the water lines that are underneath the bus from freezing and how to make sure we have water that is hot enough to enjoy taking a shower on a chilly day. Given that on demand water heaters can only raise a temperature so much, I am considering how I might be able to have an auxiliary tank in the living space that maintains 5-10 gallons of water at room temperature.

So, this is actually quite simple, but takes a little more work. I am assuming you are still in the planning stages and are not heavily into the build.


How about a subfloor with a radiant floor heat setup, insulated, with a second circuit of your other water lines to keep them above freezing?
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Old 10-28-2020, 02:23 PM   #7
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Originally Posted by CHEESE_WAGON View Post
So, this is actually quite simple, but takes a little more work. I am assuming you are still in the planning stages and are not heavily into the build.


How about a subfloor with a radiant floor heat setup, insulated, with a second circuit of your other water lines to keep them above freezing?
Iím not sure I follow you entirely. I have three 46 gallon tanks that we are mounting laterally in the basement just behind the fuel tank and in front of the differential. This is a rear engine bus. I will be boxing and insulating the tanks, and there will be radiant heat for the tanks with the heat generated by our diesel heater. That sounds like what you are describing. Keeping the lines from freezing sounds like a recirculating circuit could work, but Iím still trying to comprehend the full workings of that system, and whether it is more efficient than wrapping the water lines with heat tape.

The last piece I wish to prepare for is when the on demand heater cannot move the water temperature from a presumed ambient temperature that is not high enough for our Girard on-demand heather to reach a comfortable temperature for showers. One possible solution is a secondary heater that can kick the temperature up higher when needed. Iím still spitballing, because I donít know what I donít know. But setting up the water tanks is rising toward the top of the to-do list, so Iím trying to get a plan together now.
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Old 10-28-2020, 03:57 PM   #8
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You mentioned water lines, which was confusing, I assumed you were focusing on plumbing. What I was suggesting was to largely route your plumbing in a radiant subfloor to reduce exposure.

Newer semi tractors often have fuel tank heaters, and some have padded tank protectors to help keep the cold from gelling the fuel, I am sure something along those lines could be made to facilitate keeping water tanks from freezing.

I can also tell you from experience that the vibration of a diesel running can help to keep liquid from freezing, something I was enlightened to when hauling a load of Gatorade in 25 degree weather. Gasoline engines are typically smoother and may not help with this.
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Old 10-28-2020, 04:12 PM   #9
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Originally Posted by TheArgobus View Post
On my future bus conversion (if I ever do another one), it'll have heating mats under the water tanks like this (https://www.amazon.com/12V-Flexible-.../dp/B074SXKPZL). You don't need much, just enough to keep the water above 32 degrees. As it stands for me, I don't travel where it gets below freezing.
I am much more likely to go with your advice to follow the warm weather. If I need heat to get through the night, I'm pulling up stakes and moving south as soon as I wake up the next morning!

You realize those heat pads are less than 2 inches by 4 inches? How many of them do you plan on using?
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Old 10-28-2020, 05:27 PM   #10
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Quote:
Originally Posted by CHEESE_WAGON View Post
You mentioned water lines, which was confusing, I assumed you were focusing on plumbing. What I was suggesting was to largely route your plumbing in a radiant subfloor to reduce exposure.

Newer semi tractors often have fuel tank heaters, and some have padded tank protectors to help keep the cold from gelling the fuel, I am sure something along those lines could be made to facilitate keeping water tanks from freezing.

I can also tell you from experience that the vibration of a diesel running can help to keep liquid from freezing, something I was enlightened to when hauling a load of Gatorade in 25 degree weather. Gasoline engines are typically smoother and may not help with this.
You were right the first time, I am talking about water lines.

And Iím sorry that this thread seems to be hijacked. It started with my solution for keeping my water tanks from freezing.

To clarify, we have 3 water tanks, 1 grey and 2 fresh, that we are mounting in the basement behind the fuel tank. This location is between the wheels and centered under the bus, which should keep the center of gravity low and centered. It also allows me to run drains on both the driverís side and passengerís side to the grey tank. All 3 tanks are going to be contained in a single insulated box. The box is going to be heated by a hot water line, with the water provided by our Dickinson Newport Diesel fuel heater with a coil that will heat the water for warming the water tanks.

I donít expect this 5-10 gallons of water that will be circulating through the pex pipe that will line the bottom of the insulated water tank box to bring that water up to 72ļF, but I do think it will keep the tanks from freezing whenever we are running the heater.

The water lines that Iíll be running for warming up the tanks will not warm the water lines that will be running under the insulated floor. The water line from the Dickinson diesel heater is completely isolated from our fresh water supply.

So my first concern is that the lines that will be running from the fresh water tank and being distributed to the shower on the driverís side and the kitchen sink on the passenger side need to be kept warm enough to prevent freezing. A recirculating system might work for this, also heat tape might work.

My second concern is that my wife wonít be pleased with the temperature of the shower if itís not hot, which I predict will happen if weíre in conditions where the weather is cold enough to freeze water. So Iím trying to anticipate what I might be able to do in those instances.

I really should have started a separate thread to discuss these issues. My apologies to the original poster. I hope that at least there is some value in sharing my tank warming solution.
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Old 10-28-2020, 05:33 PM   #11
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Originally Posted by CHEESE_WAGON View Post
What I was suggesting was to largely route your plumbing in a radiant subfloor to reduce exposure.
Okay, I see what you are saying. I can route the water lines above the metal floor of the bus, and within the insulation layer of the subfloor. My tankless heater and water tanks are still below that level, so there will be some water line exposure to cold weather. Thatís the part I am concerned about, keeping those lines from freezing.

I might be overthinking this, but a few years ago I had a mouse use the insulation in the walls of my log cabin to build a nest and it exposed the water line to my toilet to the freezing weather. The line broke, I had to take apart the wall to repair it. Twice. I finally just encased the whole line in urethane foam, and I havenít had that particular mouse problem since.
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Old 11-09-2020, 11:06 AM   #12
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Here is the solution I am working on

I have been engineering a way to keep my water tanks mounted below the bus from freezing, and this has led me to developing a radiant floor for my undercarriage water storage. The medium will be water, and it will be heated by our Dickinson Newport Diesel Heater because if it's cold enough to freeze our pipes, we will definitely have the heater running!

I don't know a great deal about fluid dynamics, but I decided to take a cue from the thermal bridging issues we have with insulating busses and built this contraption so that the transfer of water from PEX to metal is optimized by having metal on all sides, and then a large, heavy heat transfer plate that will act as the floor for the tanks themselves.

I still need to insulate, cut the top, and make the cutouts for the front panel where all of the water will be going in or coming out through various ports. The box itself is not super heavy, being made from HDPE sheet and riveted aluminum, but all will be supported by unistrut and snugged up against the front-to-back beams in the center of the bus.
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Old 11-09-2020, 02:45 PM   #13
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Nice job !
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