Backyard Aquaponics
A place to discuss aquaponics

After buying then returning a $12 5' long 4" diameter PVC pipe for use as a tower, I have been wondering if it would be easier and cheaper to modify a metal stovepipe or other. Which metals are OK and which are verboten?

OK, how about lead?

Lead was considered fine many hundreds of years ago, but I think we have learned since then...

Metals seem to bring along with them a whole new range of problems in their reactions with water. Water in the system can be acidic and then with different metals mixed together in the same water you can end up with some major reactions happening.. I have seen whole large books on metals and boats and how to protect them from corrosion, there were some scary stories about boats that had used different metals below water lines and how the chemical reaction of the water and different metals made the boat fall apart within a matter of a few months...

Personally I would go for safe plastics wherever possible....

I was kidding about the lead, haha. I read a little about aluminum today and it seems that it is the most abundant metal of all, and that the only people who have had problems with it have been older folks with renal problems to where the aluminum couldn't be eliminated from their bodies, then it interfered with the use of other metals like magnesium, etc.

I am wondering about powder coatings, too, if exposed metals are a problem then anodized might not, depending on the makeup of the coating. If powder coated metal like aluminum isn't cheaper than PVC then so be it. If metal were allowable I think that could open up all kinds of configurations, since you wouldn't limited to tube shapes like with plumbing pieces. Imagine a bronze turtle above a koi pond, full of clay balls, sprouting evergreens like a topiary...

DD, i know i know, you keep reminding me of the heat exchanger i want to put in the system. Stop it.

Power coating is expensive, plus i think it help insulate the metal. Plastic is a good safe chice, but it has S@#T thermal conductance.

All in all i think Stainless steel is the go, just not (at all ) as easy to work with as copper.

Steve

Hi S:
Have you looked at the pre-made heat exchangers for solar hot water heaters? They look like little stainless heater cores. Then again if heater cores for cars are steel that might be an option...

S, i like that!

No have not looked at them, always just assumed they would be copper.

With steel you'll probably have rust issues..........

For towers, I am now thinking about terra cotta. It can be made into any shape you want, then hardened, and it doesn't have nasty chemicals in it. It would be super easy to make a pottery tower with circular holes to drop net pots into, and then pull out when the plant is retired. Plus, chicks dig it!

http://www.artforgardens.com.au/gardenart.asp?GC=12

p.s. You can get a home powder coating gun for $100; still a question about food-safe coatings, but they must exist...

http://www.eastwoodco.com/jump.jsp?item ... itemID=458

The rust issue would be true, but then again you are putting iron into your system surely??!!

Hey AM:
I don't think rust would be a negative either, unless it went nuts. I have been wondering about metal for towers, S is talking about solar heat exchange. For heat exchange I would be perfectly fine with using a poly tube wound in the tank (assuming it is less than $12 haha). Just wondering if there are cheaper materials than plastics. Pottery has an appeal, cave-man-style. (cue Hoodoo Gurus: "Mars Needs Guitars")

I read somewhere that it pisses machinists off when an engineer/designer specifies stainless when regular steel will do, because it is more work to machine, or something.

Lead: Very Bad
Copper: Bad for fish
Aluminum: May be bad
Steel: Too rusty
Stainless: Too difficult to work with
Tin?
Brass?
Zinc?

Brass is the term used for alloys of copper and zinc in a solid solution. Typically it is more than 50% copper and from 5 to 20% zinc, in comparison to bronze which is principally an alloy of copper and tin. Despite this distinction, some types of brasses are called bronzes. ....

W ondering if the high levels of copper in brass would be problomatic... gut says yes

Zinc
Even though zinc is an essential requirement for a healthy body, too much zinc can be harmful. Excessive absorption of zinc can also suppress copper and iron absorption. On the other hand, the free zinc ion in solution is highly toxic to plants, invertebrates, and even vertebrate fish

Tin
The small amount of tin that is found in canned foods is not harmful to humans. Certain organic tin compounds, organotin, such as triorganotins (see tributyltin oxide) are toxic and are used as industrial fungicides and bactericides....

So aluminum and steel? Does anyone have a big problem with using aluminum, and why? Please provide links... Googled this one, skipped the alternative medicine link which was the first one ranked: http://www.emedicine.com/med/topic113.htm