Can I use a 55gal plastic drum for potable hot water?

[Number21]

I'm working on a combination solar/wood boiler hot water system for household hot water and air heating. I'm wondering if it's safe to use an insulated food grade 55 gallon plastic drum as a storage tank for potable hot water, say around 150F max? Should I be worried about anything leaching out of the plastic at high temps?

Also, for general heat storage but not drinking water...will plastic drums be able to handle 212 degree water for long periods?

[freeEnergy4me]

I'd be interested in how you are getting the water to 212 F.

I have no idea about the plastic, sorry. Contact the supplier about the 212F?

I have been thinking about this all night. But it seems like solar heated water in a thermally-insulated container could provide heat in the evening? A way to store the heat?

My electric bills are now way down because of my panels....now I have to figure a way to get rid of that expensive natural gas.

[scottsAI]

Hello freeEnergy4me,

If interested in low cost solar heating, hope you have checked out:

http://www.builditsolar.com/

Many low cost solar projects.

The "Half program" is a must read to start, then think about solar heating.

I live in MI, where you at?

Have fun,

Scott.

[Number21]

I'll get the water up to 200-ish using the wood boiler. The input water from the solar system should get the water over 100F, which will be enough to heat my pool, then the 100 degree water will be heated as necessary with wood in an outdoor boiler. I'll leave my regular old gas water heater on standby incase I run out of wood or something breaks down.

[terry5732]

These drums are usually blow mold or rotary molded polyethylene or polypropylene. The resins usually are about 350-400 degree melt. Long term 212 storage may cause them to degrade and get brittle as will sunlight. Plastic doesn't last very  long in environmental exposure, keep it covered. PE and PP are commonly used in food packaging and are no more harmful than candle wax. Your plastic food baggies, including the kind of stuff you put in the microwave, are made of polyethylene. Drinking 212 degree water may be harmful.

[Capt Slog]

I used to test water as part of my last job.  The water came in plastic bottles and always had traces of the plasticiser (phthalates) that had leeched out of the plastic; this was so regular that it was used to show the instrument was working correctly!

I mention this because I'm sure that this leeching process will be accelerated if the water is hot.  The result of losing the plasticisers from the plastic is that it will become brittle, the same effect as seen when the plastic has had lots of UV.

I'm interested to see how you get on with this, as it's something I've considered too, but not up to those temps.

It's been possible to buy plastic tube in the UK for domestic water (including hot water) for over ten years now, so someone must have got around the problem I'd hope!

.

[Number21]

Yeah, that's what I was worried about...I've heard about stuff leaching out into food and water from plastic before. Is there any cheap test kit I could buy to test for plasticiser in the water?

Then again maybe I'd be better off just running fresh water through a copper coil in the plastic drum.

[zeusmorg]

  Personally there is no way i would attempt to use a plastic barrel for pressurized storage of hot water, sounds like a disaster waiting to happen. There is a reason that steel tanks are used as hot water heaters, and even those have burst after internal corrosion.

[Number21]

Actually I was going to use a pump to suck water out of the hot water drum and produce pressure, so the barrel wouldn't be under pressure. But I'm liking my copper coil inside a drum idea much better anwyay.

Anybody have any thoughts on cheap and/or recycled materials to use as insulation for these barrels?

[TomW]

#21;

Fill the drum with sand with a copper coil / loop in it no plastic contacting water and if it gets hot the worst thing will be a droopy barrel.

Just an idea off the top of my head.

TomW

[thirteen]

hot water tank blanket or regular isulation or take the skin off of a couple of old water tanks and use the insulation on them with some duct tape. Put in a wooden  box and fill it with sawdust putting a lid on it. I would try and call the manufacturer and ask about the heating of the water in the barrel. Or even take one day of advertizing from one of the people whinning about each other, that are running for president and you could wrap it in hundred dollar bills about 4 inchs thick.

[walsdos]

Tom, I used to think the same  but a little research revealed the following.

 Regards

Walsdos

AND THE ANSWER IS:

BOTH THE WATER AND ICE = 2 CAL PER DEG C

Specific Heats of Various Substances

Substance

 Specific Heat

(cal/gram °C)

 Specific Heat

(J/kg °C)

water (pure) 1.00

 4186

wet mud 0.60 2512

Ice (0 °C) 0.50 2093

sandy clay 0.33 1381

dry air (sea level) 0.24 1005

quartz sand 0.19 795

granite 0.19 794

Note: 1 calorie = 4.186 joules (both are units of heat (energy))

 Q: Which has the highest heat capacity:

2. grams of pure water
   
4. grams of ice at 0 °C
   
10. grams of quartz sand   ANSWER
    
    

Q: Which will become warmer:

adding 10 calories to 1 gram of water

adding 10 calories to 1 gram of quartz sand  ANSWER

The difference in specific heats between land and water creates the sea breeze circulation

[zeusmorg]

 If you're looking for really cheap insulation for the outside of the barrel, expanded polystyrene (styrofoam) is usually free for the taking, used as molded packaging.  

 It does have excellent insulation properties, however it can't withstand high heat. The melting point is 240 c. however lower temperatures can do damage.

 As long as you're just using the barrel for low pressure then I don't foresee a problem with copper coils inside for heat transfer.

[GaryGary]

Hi,

I don't believe that the typical plastic barrel will hold up to the 150F let alone the 212F.

John Canivan likes using this type of barrel for solar heated water storage.  I believe that he says they start to soften up at around 130F.

You could email him and ask -- his website is:

http://www.jc-solarhomes.com/

Or, post the same question on the Yahoo SolarHeat group that John moderates.

Polypropylene holds up to higher temperatures better -- you may be able to find a barrel made from it.  But, I don't think that even a polypropylene barrel would take pressure.  

Gary

[freeEnergy4me]

I'm in Detroit. Most of those projects are paid sites. I'm kinda cheap so I'll take what I can get for free.

[scottsAI]

So will I. I live in Brighton, MI.

Not sure what you mean by paid sites? All the links are to projects, the reading for most are Free. Most are very good projects, I have gotten lost there for days. Wife had to come get me!

Have fun,

Scott.