How to filter a wood-fired tub in an off-grid backcountry location?

[fishnaked]

Hi,

Last December, I built a wood-fired hot tub from an old steel tank. During the process, I ended up welding some new, rust-free metal inside for brackets, etc. I also wire brushed the inside down to bare metal in places. I didn't take into account just how much the new rust would affect the clarity of the water. After only 2 weeks, the water was so rusty that visibility was down to just ~4" or so.

It's the new rust creating the problem. I believe that after changing the water a few times, I will have less of an issue... after the rust seasons, for a lack of better way of describing it. However, short of hauling fresh water in, in the back of my 4x4 truck, my only water source is from a rainwater/snowmelt harvester... and the tub takes up a significant portion of what I'm currently able to harvest.

I'm hoping to find an inexpensive way of filtering out this rust, on a trip by trip basis. In other words, given the tubs remote location (no electricity), and the fact I do not live there, I'd like to figure out a way that I could remove a good portion of the rust in a short amount of time (~1 hr). My water doesn't have to be crystal clear. I would like a good improvement though. :-)

I have a generator and a 3/4 or 1 horsepower water pump. Could I somehow rig up a filtering system with those two things? I suppose I could rig up some sort of solar system... but, for the sake of saving some money, I'd prefer to work with what I have... if there was a way.

Anyone have some ideas?

Thanks,
FN

[Beck0101]

Were this my problem to solve I'd probably try to find a way to rig up a thermo-siphoning filter.  Get a standard 10" activated carbon "whole house" water filter, plumb it from low on the tank to high on the tank, paint the filter lines and filter housing black, place in full sun, and see what happens.  I don't know if you'd get enough flow with this to push water through a carbon filter.  Worst case you could surely install a sediment filter and get flow.  Better than nothing.

You could also pretty easily add a water pump and run this with your generator when you're around.  Might take more than an hour, depending on size?

I've used standard big-box whole house water filters to remove iron and it's been pretty effective.  A standard hot tub filter is not setup to do that kind of filtering.

Depending on your level of commitment to this tub you might also consider coating the inside with a urethane or something similar.  Especially if you ever plan to try to treat the water with chlorine or the like.  A tub of water in the woods is going to end up with a lot more than just rust living in it...

[fishnaked]

Thanks, Beck! I like the thermo-siphoning idea. A lot. There's already a pipe down low and up high that I could easily connect to. I'm wondering if I'd get any flow at all though? Also, I could only use it during the warmer months (wouldn't want it to freeze and break, losing all my water).

My tub's capacity is 200 gallons but only has ~175 gallons in it now. I looked at my pump and it is smaller than I thought at 1/2 HP. Still, it pumps 10.5+ gallons per minute... so it would only take 16 minutes to cycle all the water through a filter one time. If I could figure out a filter system that could be washed and reused, I could cycle the water through once or twice, soak in relatively clean water, take the filter home, rinse it, and take it back to this tub on my following visit for a repeat.

If I could find something to coat the inside that would hold up in this application, I would consider doing just that. However, I talked to the folks at the local paint store about this when I was building it, and they were not aware of anything they thought would hold up.

I am treating the water in the same manner as I do with my wood tub at home: ~1/2 cup of 35% hydrogen peroxide after each soak.

Thanks again for the info. I'd appreciate any more ideas you may have.