Newbie question - Storage tank -Old propane tank?

SystemSystem Posts: 2,511 admin
Hi all ...great forum here. As a newbie to it ...I have a question that is a carryover from research on putting in a wood boiler heating arrangement. Because of some concerns I have on the boiler system designs (cost for one) ....there is one element that is a common solution in those systems for heat storage. Used propane tanks are used a lot to store heated water for later use. They are generally installed in a pressurized way and then put in a well insulated environment to keep the heat in them .....could this be used with a solar water heat source system taking the place of the boiler? These tanks can be had with small to large capacities and I personally know where I can get a 360 gallon ...and probably a 500 gallon tank for little to nothing (I am located in Tennessee). Since the water storage tanks are a large expense in the solar water heat systems as well .....it could be a way to reduce paypack time on this type of installation. I plan to use the hot water for radiant heat as well as potable water ...the water in the propane tank would be in the closed loop for the radiant heat ...heated by a heat exchanger, then the potable water would also be heated by a heat exchanger in a gas hot water tank with the gas as backup. I haven't got it all figured out yet ....but would like to know if I could expect something like 4 solar collectors to take care of heating all this water ....and if the propane tank could be a part of the design of the system. Again the gas water heater would be the fallback when the solar was not filling the need. Thx, RH

Comments

  • mike95490mike95490 Solar Expert Posts: 9,011 ✭✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    having several hundred gallons of even tepid water, would reduce your conventional water heating costs. Maybe stacking 2 tanks, 1 a conventional water heater adapeted with a solar heat exchanger, and the waste heat from that, feeding the "propane" storage tank, could, except for a series of cloudy days, nearly reduce to zero, your water heating costs. Scaled large enough, hot water can warm your house slab, and reduce your home heating bill too.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    One issue to pay attention to with any tank/hot water issue is pressure and the integrity of the tanks. Tanks that have failed pressure test for holding propane may be fine to hold low pressure water, but I would be very careful about using any untested tanks with any significant pressure. 500 gallons @ 5psi is a big leak. 500 [email protected] 50psi is a disaster.

    Icarus
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    would propane tanks be susceptible to rust???

    ive had the same idea of using them for hot-water storage (unpressurized for me though...)
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    Here in Canada, what we call the 20 pound cylinders (I believe they're called 5 gallon in the USA) are supplied with a blow off set for 375 PSI, while the larger cylinders, such as 500 gallon, are supplied with a 325 PSI blow off. It would follow that the cylinders are normally capable of withstanding much greater pressure. Up until they are taken out of propane service, their inside would normally have been dry, thus would not be rusted inside. Outside however can become quite pitted, especially if they have lived near salt water and that can easily be seen. I would suggest that if protected by a proper water system blow off of 75 PSI for example, there should be no problem with explosions. When was the last time anyone has actually seen a regular hot water tank that has exploded, causing damage? Yes, every once in a while we hear of such a story, but investigations indicate either no blow off, or a malfunctioning one, along with a defect that allowed the heater continue to heat even after the water was boiling, and building up pressure, which resulted in a BLEVE. (Boiling Liquid, Expanding Vapor Explosion)
    I strongly suspect that if properly protected from over pressure and over temperature, any leak would be of the typical pin-hole, or nail hole type.
    Granted, the propane cylinders were never intended to hold water, so an insurance company may use that fact to refuse any claim, but that's another issue.
    Cheers
    Wayne
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    Forgot to mention, if an anti corrosion anode rod, such as is used in standard hot water heaters, is installed in the propane cylinder, (by you) any rusting while in water service should be greatly reduced. Perhaps even install 2, 3, or 4 in a 500 gal tank, and check them every year or so, replacing as necessary.
    Just a thought.
    Wayne
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    I agree with Wayne, that a propane tank is a more robust tank than a domestic water tank. On the other hand, I don't know if you could ever get rid of the odorant from the tank. If it has been in propane service for a while the amount of odorant would be significant.

    My gut feeling is depending on the the volume, a large plastic or steel water tank would be way simpler assuming that you don't need to have the tank under significant pressure. If all you are using the water for is a circulation tank, the need for high pressure is reduced. A 1000 gallon plastic septic tank can be had fairly inexpensivly. We installed a 1500 gallon tank at a bush camp to use for gravity water, and it cost ~$500 if memory serves.

    Good luck

    Icarus
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    OH, good point on the odorant there Icarus. Hadn't thought of that at all.
    Anyone have any experience with that end of it? I'd like to know too.
    Wayne
  • BB.BB. Super Moderators, Administrators Posts: 31,038 admin
    Re: Newbie question - Storage tank -Old propane tank?

    I took a look around at how to deoderize a tank (methyl mercaptan or methanethiol; CH3SH), and did not find anything simple...

    Apparently it is a problem even for scrap recyclers because the mercaptan gets into the pores of the steel--and people will report natural gas leaks near places that scrap out propane tanks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    Thanks for that Bill - - - I think. LOL
    Yeah, I knew it was bad, but didn't realize just how bad.
    Your info indicates it's probably unusable for anything other than heat storage as part of a closed system.
    However, just remembered, I've been using a "100 pounder" (25 gal US?) as a tank for my compressor for about 10 years now, and can't remember the last time I smelled the mercaptan. I know it was strong at first, but must have flushed out over time and I didn't notice it happening, just now realized I haven't smelled it for years.
    I have no idea how long it took to dissipate.
    Wayne
  • mike95490mike95490 Solar Expert Posts: 9,011 ✭✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    From another list:
    http://listerengine.com/smf/index.php?topic=2890.30
    It stinks, and takes a while to wash out:

    "i had no idea for sure whether it was flammable or not, but i do know that crap is hard to get rid of sticks forever too the tank i cleaned out had about a half gallon of it in there!
    i flushed it with water, then hot water at a carwash, then again with dawn dishsoap using a whole bottle even after all that it stunk so bad.
    because i was using it as a vacuum tank for pickin up waste motor oil i figured it was good enough the waste oil guy complained that my oil sure smelled bad the first pickup"

    "Also confuses flies, and they come swarming, looking for a corpse."

    "Bob said his had a bunch of the stink oil in it....I've never seen but an oily film of yellowish goo. Mix alcohol with the water and it comes right out."

    ""The ethyl mercaptan in the bottom of the tank is easily dissolved and washed out of a tank with another alcohol like methanol, ethanol (cheap vodka?) or isopropanol (rubbing alcohol). Water won't dissolve it at all, but diesel, kerosene or gasoline might.

    FWIW, when bees are provoked, they target CO2 just like mosquitos do, so maybe a good strategy if you're robbing a hive is to hold your breath. If the bees get aggressive, run fast. They can fly only abourt 10 mph. As long as you don't exhale, and keep hoofing it, you should be fine. But don't come after me if you get stung, because I haven't tried it.""


    So that's my story about a story about washing a tank out.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    Hey, thanks Mike, Very interesting stuff on the stink. Now, where did I put those tweezers, I have a bee stinger to remove - - - :D
    Wayne
  • System2System2 Posts: 6,290 admin
    Re: Newbie question - Storage tank -Old propane tank?

    Been reading some of your replys about using propane tanks for hot water storage and have learned some new things. I have an outside gasafication furnace and three years ago added an 800 gal stainless steel (milk bulk tank) for storage. I stored water at 190 degrees and 12 to 15 pounds of presure. I live in northern Vermont and only needed to have a fire about 6 hours per 24 to heat our 2400sq ft house and the domestic hot water. I use around 5 cords of wood per winter. I just found leaks from hairline cracks in the stainless steel and have stopped using it.
    I am now preparing a 500 gal propane tank to do the job. One problem so far is my wife will not let me in the house because of the smell..... Does anyone know how to get rid of the smell? My shop stinks too.
  • BB.BB. Super Moderators, Administrators Posts: 31,038 admin
    Re: Newbie question - Storage tank -Old propane tank?

    We have kicked the question around here before--I never saw a good way of neutralizing the Methanethiol (also known as methyl mercaptan) odor.

    It has been reported that the odor has been detected down into the 0.002 parts per million range (2 parts per billion).

    I don't know what methanethiol will do to the other components in your hot water system even at low concentrations. You might have issues such as:
    Bacteria in oxic and anoxic environments can also convert methanethiol to dimethyl sulfide (DMS), although most DMS in surface seawater is produced by a separate pathway. Both DMS and methanethiol can be used by certain microbes as substrates for methanogenesis in some anoxic sediments. Methanethiol is a weak acid, with a pKa of ~10.4. This acidic property makes it reactive with dissolved metals in aqueous solutions.

    I would suggest that you avoid using an old propane tank for any other purpose other than storing propane.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    I think the reality is that you might likely NEVER remove the odor. I suppose you could argue that if the water is in a sealed circulating system, (and you are not going to use this for any potable water!) there may be no issue with the system. If however your hydronic heat system has bleed valves that vent into the room you are going to have a problem.

    I assume that your interest in LP tanks is that they can be had cheaper than other alternatives. What would you have to do repair/upgrade the SS tank? My worry that an abandoned LP gas tank might not have a lot of life left when subjecting it hydronic heat.

    Tony

    PS A little reading off site reveals folks that have turned LP tanks to Air tanks and they claim the odor goes away after a good long while.
  • TnAndyTnAndy Solar Expert Posts: 249 ✭✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    I bought an old 500gal propane tank to use in the self designed hydronice heating system I've had in my house for 25 years. Old tank was one they tool out of service at the propane place and sold it to me for scrap ( $100 ). Data plate on it said the wall was 3/8" thick steel, and was pressure rated for 350 psi at the time of manufacture ( which was 1953 ).

    The smell was pretty heavy at first.....I flushed it a couple times with water, and that seemed to handle most of it. When I drained it in later years occassionally for maintenance, the water had no smell. I didn't do anything special for rust protection, and it's been in service now 25 years with no problems. Max temp on it has been close to 200, and pressure about 15-20psi. I DID find I needed a large air tank ( I used an old 50 gal water heater tank ) for expansion for that much water, or your pressure relief valve will open quite regular and dump hot water........located that tank high in the system so it never held water....just air.

    This system was for heating only, not domestic hot water.
  • solarvicsolarvic Solar Expert Posts: 1,053 ✭✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    A few of the Amish around use propane tanks for air tools and fans. I was at a spring school fund auction for thier school and the fans with an air motor bring about $400.00. They aren,t allowed to use electric. Noticed 1 charginghis batterys for buggy with a solar panel. S:Dlarvic
  • peakbaggerpeakbagger Solar Expert Posts: 341 ✭✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    The folks that frequnet the forums on Hearth.com are frequently discussing propane tanks for water storage, might be worth searching their forms.
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: Newbie question - Storage tank -Old propane tank?

    vtnorth, I use a TurboBurn, 750 gal capacity, atmospheric pressure boiler. Burn 2 hrs per day, 200 f. Think the propane tank is a great idea. Why 12-15 PSI?

    If you can run at atmospheric pressure I would try to repair the milk tank if not, then propane tank and insolate with spray foam insulation.

    Guest, Great idea, if a close loop system, use anodes and automotive antifreese (has rust inhibiters). Insulate with spray foam.
Sign In or Register to comment.