Backyard Aquaponics
A place to discuss aquaponics

the fact that these tubes are black probably is a protection in itself against UV:
http://www.coleparmer.com/techinfo/tech ... htm&ID=834
How to Avoid UV Degradation
There are several ways of avoiding UV degradation in plastics — by using stabilizers, absorbers or blockers. For many outdoor applications, the simple addition of carbon black at around a 2% level will provide the protection for the structure by the blocking process. Other pigments such as titanium dioxide can also be effective. Organic compounds such as benzophenones and benzotriazoles are typical absorbers which selectively absorb the UV and re-emit at a less harmful wavelength, mainly as heat. The benzotriazole type is good, as it has a low color and can be used at low dose rates below 0.5%.
The other main mechanism for protection is to add a stabilizer, the most common being a HALS (Hindered Amine Light Stabilizer). These absorb the excited groups and prevent the chemical reaction of the radicals.
In practice, the various types of additives used are in combinations or are compounded into the original polymer to be produced as a special grade for UV protection. It may be attractive to add antioxidants to some plastics to avoid photo-oxidation, but care must be taken that the antioxidant chosen does not act as an UV absorbent, which will actually enhance the degradation process.

http://www.inplexplastictubing.com/materials.html
POLYETHYLENE:
LDPE-Low Density
Low Temp Flexible UV Exposure LLDPE-Linear Low
Flexible UV Exposure MDPE-Medium Density
UV Exposure HDPE-High Density
Rigid UV Exposure
Polyethylene tubing ranges from flexible (LDPE) to semi-rigid (HDPE). It is a very economical material which is good for tubing. It is available in FDA and in industrial grades. It has good chemical resistance, and by adding UV stabilizers, it has good outdoor properties. Available in natural (translucent white), stock and custom colors. For flexible water and air lines where barbed fittings are used, LLDPE is preferred because it has better resistance to environmental stress cracking.

Click here to view or download Low Density PDF information sheet. (34kb)
Click here to view or download High Density PDF information sheet. (33kb)

POLYPROPYLENE
High Temp Rigid UV Exposure
Polypropylene tubing (PP)is a semi-rigid, light weight, economical plastic. It has excellent chemical resistance and fairly high service temperature. PP is available in natural (translucent white), stock and custom colors. PP is also available in FDA grades. May be used outdoors by adding carbon black and UV stabilizers. PP is available in two grades.

* Homo-Polymer - Economical, rigid, high service temperatures.
* Co-Polymer - Impact modified to improve toughness, especially in colder temperatures.

Click here to view or download PDF information sheet. (31kb)


FDA regulations are (rightfully) much more stringent for materials in direct contact with food for human consumption than for animals: if there is leaching, it will leach directly into the food.
Vinyl (known to leach dangerous products from the weakeners) is readily accepted for swimming pool liners, more so for kiddie pools.
Many people use them as fish tanks in their AP systems.
I would not use it.

give me PP or HDPE anytime

Frank

An interesting design http://www.builditsolar.com/Experimenta ... ondDHW.htm

the thin black tube is LDPE
and while LDPE is a great choice, there is no gaurantee that the feed stock was not recycled LDPE, what percentage, and from what previous life.

i see no reason for the manufacturers not to use recycled

neither do I
in fact I advocate it
it is one of the beauties of PP and HDPE that they are easy to recycle
the risky material is not recycled but burnt
the less risky material is recycled into fence posts and such
I have visited a company that recycles PP from the caps of coke bottles (the red ones, they are PP) to make wall panels of.

the nature of recycling (thorough cleaning and then melting at high temperature) is guarantee enough to me that no harmful residues remain in worrying quantities which even then would most probably be encapsulated.

I am all for recycling

frank

melting of LDPE is at quite low temperature comparatively, from memory around 120C or something?

Not potable LDPE may contain other ingredients specific to the use when it was made, these are the contaminants that worry me. If they were stable at the forming temperature and process of the original stock then the re-cycling would not really deminish them

120°C (PE) is enough to kill all possible bugs
160°C (PP) is better and explains why PP is better for warm water
but I am leaving this discussion:
I have given enough arguments to defend my choice

if you don't trust recycled because of (possible) residues, buy new and pay new
if you don't trust new because of (possible) leaching, find an alternative and pay that
I stay curious as to what that might be

Frank

no one was attacking your choice just highlighting that bugs were not the primary concern for some people. People should always have a surplus of info so they can made their choice.

indeed, but not persistently negative info, unless there is an alternative

scaring people seems to be a world tendency

I like caution, not fear

Frank

ROFL, no negatives unless there is an alternative positive to give? sounds like new age psychiatry..........

If there is a possible negative it should be brought up regardless of if there is a viable alternative. Whether people manifest this as caution or fear comes down to their own personality.

People are highlighting the point that recycled feedstock for LDPE may contain undesirables.
I can not 100% guarantee that recycled LDPE are free from undesirables.
can you 100% guarantee that re-cycled LDPE has no undesirables in it?

Alternatives are irrelevant. people have the right to have all facts presented to them.

Thanks for your input.

gosh, Steve, did I really write "no negatives ... "?
I don't think so
I think I wrote "not persistently negative info ..."


????

I am well aware that there could be a risk of leaching and have acknowledged that

but there is no need to blow that out of proportion
both HDPE and PP are (TMO) good choices
I am not aware of any alternative apart from stainless steel, which has a prohibitive cost

frank

no ones blowing out of proportion, mate.

i may have persisted in my negatives because you stated things like

"the nature of recycling (thorough cleaning and then melting at high temperature) is guarantee enough to me that no harmful residues remain in worrying quantities which even then would most probably be encapsulated."

anyway, people have more than enough info now to make informed decisions based on their personal standards

I'm seaking some black pipe that is rated for potable hot water that doesn't have dire warning about keeping it out of the sun then.

So what types of pump would one point me to.........
110 V power 60 cycles
Needs to be a fish safe pump
High head, like up to the roof of a 1 story building.
Low flow, I don't know exactly how fast the water should flow for such a heating system but less than 200 gallons per hour (at said rooftop head) definitely, how much less I don't know.
Something relatively energy efficient and can't break the bank on initial cost either as work has been horribly slow this season and extra cash for AP is pretty dried up.

theres actually been a huge amount of discussion about this before in another thread, might take some looking.

all the different pipes were covered, their temperature stability and lots of other research.

lots of houses using certified potable plastic pipe instead of copper now.

There not too bad. Just push into the brass ends.