macerator in winter camping

[RT-NY]

I've been trying to figure out the best way to use the black tank on my 1999 RT 170 when camping in below freezing temps. I usually just flush with pink antifreeze and that works fine, but it requires a lot of antifreeze, which is costly and takes up a lot of space.

I'm wondering if I can use a gallon of water to flush the toilet, then use a portable macerator pump right away to transfer to a small portable holding tank (ideally something very small with, say, a 2 gallon capacity), then dump that in a pit toilet. When using my regular gravity dump, I always need to fill up my black tank all the way to make sure that everything empties out, to avoid blockages -- would a macerator allow me to successfully dump a tank after a single use?

[RT-NY]

I did not get any response to this question, so maybe I can try rephrasing it more generally: does anyone have experience using an RV black tank in winter temps with lows of perhaps 20 degrees (thought more often 25 degrees I think) for boondocking for a week or two and then dumping after that? Will the contents of the tank freeze and damage the plumbing? Will it be possible to dump?

[mloganusda]

From what I have learned, if you use your toilet in freezing weather, with no antifreeze in the black or gray holding tank, your line leading to you dump valve will freeze solid. Then when you open the valve (if not frozen shut) little to no liquid will flow because of the ice dam. If you add about 1 gallon of antifreeze to each tank, this should keep the line from freezing and you can dump. You can also add 12-volt tank heater pads to help keep the tanks contents from freezing.

[RT-NY]

Originally Posted by mloganusda

From what I have learned, if you use your toilet in freezing weather, with no antifreeze in the black or gray holding tank, your line leading to you dump valve will freeze solid. Then when you open the valve (if not frozen shut) little to no liquid will flow because of the ice dam. If you add about 1 gallon of antifreeze to each tank, this should keep the line from freezing and you can dump. You can also add 12-volt tank heater pads to help keep the tanks contents from freezing.

Thanks for that very helpful and practical suggestion! Do you think that adding a full gallon of antifreeze to an empty 13 gallon black tank and then flusing with water as normal would be enough to prevent the freezing of the line? It will get dilluted with each use I imagine, but perhaps not so much to freeze at the temps I am talking about (not below 20F).

I would prefer to add a tank heater pad as you suggest, but the black tank is hidden away, stacked up above the grey tank on my 1999 RT 170, so I cannot easily get to it, though I could add heat tape and insulation to the line and dump valve.

[mloganusda]

If you can get to the side of the black tank, a heat pad on the lower sidewall would probably keep it from freezing. The antifreeze will collect in the lowest part of the tank and line and when flushing on top should not stir up much (IMHO) and keep from freezing in the dump line. If boondocking, do you have a generator for electric power, as the heat tape requires 12 volts. What about your freshwater tank? To your first question about dumping after 1 gallon flush, liquids would be okay but not sure about solids.

[booster]

Originally Posted by mloganusda

If you can get to the side of the black tank, a heat pad on the lower sidewall would probably keep it from freezing. The antifreeze will collect in the lowest part of the tank and line and when flushing on top should not stir up much (IMHO) and keep from freezing in the dump line. If boondocking, do you have a generator for electric power, as the heat tape requires 12 volts. What about your freshwater tank? To your first question about dumping after 1 gallon flush, liquids would be okay but not sure about solids.

Also remember that you need to have enough power to run the heaters enough to keep the tanks thawed. If you don't have shore power, you need quite a lot of battery capacity compared to what most 1999 vans have.

[RT-NY]

Originally Posted by mloganusda

If you can get to the side of the black tank, a heat pad on the lower sidewall would probably keep it from freezing. The antifreeze will collect in the lowest part of the tank and line and when flushing on top should not stir up much (IMHO) and keep from freezing in the dump line. If boondocking, do you have a generator for electric power, as the heat tape requires 12 volts. What about your freshwater tank? To your first question about dumping after 1 gallon flush, liquids would be okay but not sure about solids.

I have a generator to charge my batteries -- if necessary I can run it every day for an hour or two, so that is no problem. And I don't use the freshwater tank or the rest of the plumbing in the winter at all.

I will have to take a closer look and see if I can get to the side of the black tank, but perhaps you are right about the antifreeze not being too stirred up by flushing. And I am experimenting a bit to see how dilluted anitfreeze stands up to various freezing temps.

[avanti]

The antifreeze method will work fine, but the needed ratios depend on the rating of the antifreeze and how cold it gets for how long. One thing that would help is to use concentrated propylene glycol (i.e., non-toxic) antifreeze. That will give you twice the protection when you are flushing with plain water. You can find it at Amazon and many auto parts stores.

If you go this route, just be sure that after you add the antifreeze, you run the macerator long enough for it and its plumbing to fill with antifreeze.

[GallenH]

Curious: I've camped when it got down to 23º at night and my tanks never froze even though I didn't have antifreeze. Doesn't the residual heat of the RV have some impact? And long after the engine has cooled doesn't having your inside heater on (say 65º) have an impact? I definitely don't have an insulated floor and some heat must migrate to the tanks. I've heard a cold night with high winds is worse. I've heard that running a bit of water through faucets throughout the night helps. Also turning off your water pump and just having the faucets cracked open. Does any of this have any validity?

[avanti]

Originally Posted by GallenH

Curious: I've camped when it got down to 23º at night and my tanks never froze even though I didn't have antifreeze. Doesn't the residual heat of the RV have some impact? And long after the engine has cooled doesn't having your inside heater on (say 65º) have an impact? I definitely don't have an insulated floor and some heat must migrate to the tanks. I've heard a cold night with high winds is worse. I've heard that running a bit of water through faucets throughout the night helps. Also turning off your water pump and just having the faucets cracked open. Does any of this have any validity?

It all has SOME validity. But:
The problem isn't so much frozen tanks, it is frozen pipes. More particularly, the long pole in the tent tends to be the dump valves and their associated plumbing. Sure, there is some thermal coupling between the inside of your van and the tanks, but very little of that heat is going to make it to the dump system. Plus, the smaller the container, the lower the total thermal mass and the faster you will get ice. Tanks are big and take a long time to freeze solid (you will get surface ice quickly, but it doesn't matter much). The small amount of water inside the pipes will freeze much sooner. As for the tanks, although they are more or less adjacent to the bottom of the heated area, remember that (a) hot air rises, so your floor is relatively cool; and (b) the water in the tanks is at the BOTTOM of the tanks--the rest is air, and air is a good insulator. This reduces the amount of heat that will make it to the liquid in the tank.

Finally, 23º for a few hours is not that big a deal--it takes time for all that warm metal and water to cool off, so you can often make it through a few cold hours overnight. Spending a weekend significantly below freezing (or a few hours in single digits) is a different matter.

Our van has a dedicated hydronic loop that turns on in cold weather and keeps the tanks and plumbing warm. I haven't pushed it to too far yet, but I suspect it will keep everything working indefinitely in pretty frigid weather.

[booster]

Avanti, you may have said in the past but I don't recall it.


Are your glycol loops external on all the tanks and plumbing or internal on some of them?

[avanti]

Originally Posted by booster

Are your glycol loops external on all the tanks and plumbing or internal on some of them?

I had custom SS tanks fabricated in order to maximize capacities in the oddly-shaped available spaces below the Transit. The fresh and gray tanks each have internal glycol loops. The black tank is in the heated envelope and so doesn't need separate heating. There is only a small amount of under-chassis plumbing, and it is all protected by running the glycol hoses along them, as is the macerator. I am going to wrap them all in insulation, although I haven't got around to it yet.

[booster]

Originally Posted by avanti

I had custom SS tanks fabricated in order to maximize capacities in the oddly-shaped available spaces below the Transit. The fresh and gray tanks each have internal glycol loops. The black tank is in the heated envelope and so doesn't need separate heating. There is only a small amount of under-chassis plumbing, and it is all protected by running the glycol hoses along them, as is the macerator. I am going to wrap them all in insulation, although I haven't got around to it yet.

Thanks, Avanti,


Whenever drinking water tanks and heating or cooling loop are involved there can be some very "spirited" discussions over safety factor in case of leaks. I assume you are running propylene glycol? Did you go with food grade?


Having spent many years dealing with heated and cooled tanks at work it is always interesting to see applications.

[avanti]

Originally Posted by booster

I assume you are running propylene glycol?

Yes.

Did you go with food grade?

No. Peak Sierra. The tubes have no internal fittings. Cumulative risk seems negligible.

[booster]

Originally Posted by avanti

Yes.

No. Peak Sierra. The tubes have no internal fittings. Cumulative risk seems negligible.

Does your water heater have similar (same loops maybe?)

[RT-NY]

Originally Posted by avanti

The antifreeze method will work fine, but the needed ratios depend on the rating of the antifreeze and how cold it gets for how long. One thing that would help is to use concentrated propylene glycol (i.e., non-toxic) antifreeze. That will give you twice the protection when you are flushing with plain water. You can find it at Amazon and many auto parts stores.

If you go this route, just be sure that after you add the antifreeze, you run the macerator long enough for it and its plumbing to fill with antifreeze.

Thanks! The concentrated propylene glycol is a great idea, but it looks pretty expensive. The pink antifreeze is cheap, plentiful, and widely available. My current plan for this winter is to follow mloganusda's advice and put 1 gallon of the pink antifreeze in the empty tank, then flush with water but adding an additional maybe third gallon of the antifreeze each time. It will all get pretty dilluted I suppose, but I am not expecting it to get too cold -- a freeze most nights with some hard freezes, but warmer daytime temps. I don't have a macerator yet so no problem there.

[avanti]

Originally Posted by booster

Does your water heater have similar (same loops maybe?)

It is a Rixen's Espar system. There is a primary loop with the Espar -> a flash-plate heat exchanger for on-demand DHW -> a water-air heat exchanger for heat. There is a secondary loop off the main loop (with its own water pump) that heats the tanks when it is cold. It is thermostatically-controlled. It is the same setup that Rixen's sells for under-floor hydronic heat.

[GeorgeRa]

Originally Posted by avanti

I had custom SS tanks fabricated in order to maximize capacities in the oddly-shaped available spaces below the Transit. The fresh and gray tanks each have internal glycol loops. The black tank is in the heated envelope and so doesn't need separate heating. There is only a small amount of under-chassis plumbing, and it is all protected by running the glycol hoses along them, as is the macerator. I am going to wrap them all in insulation, although I haven't got around to it yet.

Nice design! I always questioned why stainless-steel tanks are not used more often, it is a great option.

Questions:

Did you use seamless stainless-steel tubing inside/throu tanks? I assume they are not welded into tanks walls.

Is above freezing tanks temperature controlled by coolant flow control?

Your van space and water heating are connected to heat sources – primary gasoline powered D5, and Rixen heating electrical rod. My confidence in Eberspacher reliability is getting reduced with experience, how will you manage potential D5 failure while travelling?