Water tank and rafters?

[Nevada_Mike]

John,

I will be using rain water for my cabin until city services arrive.  Do you think that my rafters would support  a tank that I pump up to when the generator is running? They seem really stout! That would make a simple gravity system work. I am still waiting for new pictures.

Thanks, Mike  

[Amanda_931]

For a no--or very low--electricity cabin I'm planning on biggish tanks on the ground, then pump, by a guzzler or small battery powered pump, up to overhead tanks--hot and cold water.  Under 80 gallons total overhead in the loft.  (somewhere around 700 pounds including tanks)

Might do some belt-and-suspender stuff with the framing and beef up the framing at that end.

If someone knows a good way to rig a shower I'd be interested.  I gather that the key to flow systems rather than pressure is as large a pipe/hose as possible.  I'm looking for a watering can rose as the final bit.  The little jobs that come with the black plastic bag "solar water heaters" are pretty wimpy.

The Big Berkey filters reputedly take care of a lot of stuff, may need to do a bit of pre-filtering, but the main--expensive--filters are pretty long-lasting, can be cleaned a bunch of times.

I do have friends with a giant rainwater harvesting system--what they use for all their water, with a standard jet pump and pressure tank.  Aside from the fact that it tastes better than the local mains water most of the year, you'd never know they'd done it.

[jraabe]

I don't think mounting a tank would present too much of a load. I would set it up so that several joists or rafters share the load so the deflection isn't concentrated on just one.

[DavidLeBlanc]

Something to keep in mind: 1 cubic foot of water weighs 64 pounds.

1 gallon weighs 8.6 pounds.

[Daddymem]

Water has a density of 62.4 #/cf
and 2.31 ft/psi (you gain 1 psi for every 2.31 feet you raise a body of water up or reverse it)

[Amanda_931]

Can't use height for genuine real water pressure until you are up over 45 feet.

But you can run water down onto your head, or into the bathtub at much less.  Especially if you use as big as possible pipes.  Three quarter all the way is not too bad from maybe 15 feet.  Might have to fill a bucket and scoop bowlfuls of water over your hair at much less than that.

Cannot use an on-demand water heater, though, because that really does work on pressure, not flow.  And I'm told you don't particularly want to be close to the minimum pressure (20 psi) with one of those anyway.

[glenn kangiser]

I also like .433 lbs per foot Daddymem.  Used it a lot in my well drilling days to calculate necessary air pressure for air lift pumping wells to develop them.

Rule of thumb, 1600 cfm of air would bring up appx 1 gpcf air at 50% submersion or 2 gpcf air at 75% submersion.  Had to calc each setup to make sure I was under the compressor pressure limit or lots of noise and smoke from the screaming 500hp  Detroit- no water -- but when things were right - about 2000 gallons of water, dirt and sand would shoot up to about 100 feet into the air.  Doesn't that just get you all excited.

[Daddymem]

Yeah, it is 2.31 ft per psi anyway you slice it.  I think Amanda's point was to obtain the standard minimum 20 psi residential pressure (to pressurize an entire house) you need to have 47 feet of head.  My point is you can get some pressure for a gravity shower or tub or sink by putting the tank up in the rafters...how much pressure? .43 #/ft.

[Amanda_931]

Yep, that was the point.

I considered a water tower for right here, but all I was prepared to do was a 12 foot tower (maybe 10 feet up the till), not a 40 foot one (ten feet up the hill).  Plans are available, but it looked like all the wood would have to be milled just for the job, and the foundations were enormous, especially on the sloping hill, lots of welding for connectors.

[Amanda_931]

Does anybody know if standard poly tanks are OK with hot water?  Somewhere below 150 degrees F but maybe not much.

And does the heating and cooling tend to cause leaks in fittings near the bottom of the tank?

For an insulated tank in a loft.

[glenn kangiser]

Found this q+a Amanda.  Wondered about this myself.  Pex fittings will take the heat.  I think an old water heater tank or galvanized pump water tank possibly available used at a dump or pump installer may be better.  Or even a new one  That might hurt a little.


8. What is the maximum temperature that your tanks will withstand?

Linear polyethylene (HDLPE) storage tanks have a maximum storage temperature of 120 degrees F. Cross-linked polyethylene (XLPE) storage tanks have a maximum storage temperature of 130 degrees F.

NOTE: The leading manufacturers in this industry design their tanks based upon 100 degrees F with ASTM D 1998 calling out 73 degrees F. It is important to contact the factory when your application will continuously be above 100 degrees (ambient). The tank can be designed specifically for your elevated temperature application.

From here:http://www.safetanks.com/general_faq.html#q8

[Amanda_931]

I'm afraid you're probably right.  An undercounter electric water heater may be the best solution.  The pump tanks seem to be violently expensive.  Poly tanks are over a buck a gallon in small sizes, but not all that much over.

But a small water heater is  heavy.  

I found this site, though.  It doesn't diffrentiate between "maximum temperature" and maximum sustained usable temperature."  

Unfortunately "ask Mr. Plastic" just opens the email.

http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp

including this on the subject of polypropylene (actually another URL, but....):

"Polypropylene Quick Facts:
 Maximum Temperature: 275°F 135°C  
 Minimum Temperature: 32°F 0°C
 Autoclavable: Yes
 Melting Point: 338°F 170°C  
 Tensile Strength: 4,500 psi
 Hardness: R95
 UV Resistance: Poor  
 Translucent  
 Rigid  
 Specific Gravity: 0.90

Polypropylene Fabrication:
Great chemical resistance makes Polypropylene a popular choice for plating and chemical tanks, as well as laboratory cabinetry and semi-conductor bench tops.
This material machines well and is available in many profiles.  
Propylene is autoclaveable for usage in biohazardous environments.  
Other uses include fittings and connectors, storage containers, sinks, and hoods.
The best joining method is hot air or nitrogen welding. Can be mechanically joined with screws or rivets. Ultrasonic inserts work well."