Backyard Aquaponics
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Have been thinking about replacing PVC pipework with HDPE pipes. The reason is I'm still concerned about the use of PVC and possible leaching of chemicals. I would rather err on the side of caution. Anyone know of where to get AP size HDPE pipes in Perth, WA? any advice on the use of PVC and HDPE and reasons for/against either is also welcome. Thanks

Its more expensive and you can't stick it so you have to use compression fittings (also expensive). The large sizes are commercial, read more expensive again. All pipe internals in the system get coated with bioslime. If there was any breakdown it would be due to uv exposure, but its very slow. The same happens with HDPE.

what chemicals are you concerned about though?

i had a system running for 5 years with pvc pipe, and i had the produce professionally tested in a lab for organochlorine, organophosphate, PCB and 8 heavy metals and nothing but zinc showed up above the limits of detection at 0.001 mg/kg.

the zinc was 0.05 mg/kg, so you'd need to eat 2 kg's just to get the RDI.

it'd be interesting joel or someone went further with this and did some more extensive testing, it might put the concerns about pvc to bed once and for all.

pvc is only really dangerous if you burn it. that's because of the chlorine gas released. even if the chlorine leached out of the pvc then it would just be broken down by sunlight. as long as you're not burning it you should be 100% safe.

There is not any significant evidence that Non flexible PVC products, ie rigid, are a health risk. There fore from direct effects there are no grounds related to health for not using PVC.

If you want the extra tree huggin hippy feeling of HDPE it comes from the fact that PVC is rather noxious to produce. If you use it in your system you are adding to the demand for PVC products which adds a bunch of nasties to the environment. Having said that so does almost all your other modern life style choices.

Gram for gram HDPE is less environmentally damaging than PVC.

The thing is though, that the HDPE fittings that you will use weigh a lot more than the PVC ones. Now this is my opinion I don't have a study to base this on but I suspect that because they are so much heavier using so much more plastic than the PVC equivalents that they are in fact a worse environmental choice for the discerning tree huggin, commie hippy.

In our commercial system we are using HDPE for environmental reasons. It is a more benign material but the butt welded fittings use less material than the equivalent PVC fittings* so you get an additional benefit.

*HDPE butt weld fittings are the same size of the pipe that you use them on. PVC fittings are larger than the pipe you use them on because they are a socket fit.

Most amusing Stuart your decision to use HDPE would have nothing to do with the fact that in a commercial system HDPE will bend and is more robust.
As far as I am aware HDPE pipes have a thicker wall diameter but a lower SG than PVC. HDPE will float just, PVC will not, so for certain applications PVC is more useful in others HDPE.
Being a tree hugging commie hippy I use PVC a lot.

LOL

Sure it is but that is not why we decided to use it. A number of the potential systems that have been asked to express an interest in building are in the EU and they have shifted from PVC to HDPE and some other plastics for environmental reasons. Since it is good to "begin with the end in mind" we decided to start as we planed to continue and go with HDPE. Yes it costs more but there is a real sustainable benefit.

As to the walls being thicker:

* class PN 4 PE 100 HDPE NB 100mm wall thickness 2.7mm.
* class PN 4.5 PVC NB 100mm wall thickness 2.5mm.

Yes they are but there is not a lot in it. Also the class PN 4.5 pvc is not a standard product so it costs at least double, if available, what the standard PN 6 or PN 9 PVC costs.

The PE 100 is soon to be superseded by PE 120 which is stronger and therefore has a thinner wall thickness. Also the PN 4 HDPE is the standard drainage product. The Standard PVC drainage product has a wall thickness of 3mm (DWV PVC NB 100mm, SN6) and is not pressure rated.

The pressure rating of PN 4 means that the HDPE fittings and pipe can hold the equivalent pressure of 40m of water depth. You are seriously unlikely to encounter a pressure even approaching this pressure in an AP system.

Do you use regular PVC or pressure PVC timmy?

Was this you as a young adult Stuart?

Ehhh, no.

I really don't like the way many democracies seem to have split into two party systems. I like ideas that work and the two party system seems to promote ideas that fit ideology.

The so called right parties favour economic rationalism even when the policies they develop based on an incomplete and lazy bean counting approach cause them to cost the public purse more money.

While the left seem determined to restrict business so that the economy is stifled and as a result there is not the tax revenue to fund the public programs they champion (that's a bit simplistic but oh well).

Having said that let us not forget that it is the economic reforms that the Hawk and Keating Government made (liberal for our American friends) that are majorly responsible for the strength of our economy today. While those reforms were improved upon and continued by the Howard government and his leadership of the liberal party (conservative for our American friends) Hawk and Keating did much of the heavy lifting involved in improving the efficiency of our economy. There is no way that Australia would have been in such a good position to take advantage of the recent growth in China without those reforms.

The rights obsession with reducing spending just seems absurd to me. At a household level what would happen if you cut your expenditure by ceasing to pay for insurance, house repairs, vehicle maintenance, work clothes, etc. Yes your expenses would go down in the short term but the long term cost to your future expenses and future income would be catastrophic in the long term.

In so many areas our governments need to increase their spending and in doing so they will in the long term decrease their budget pressures. Preventative dental and health care will over time drastically reduce the budget pressures on acute health care, police, judiciary and penal system. While adding to the productivity and hence the tax-ability of those who would benefit from such care.

Currently we are one among a number of families effected by cuts to the transportation budget by the Victorian education department. We can not afford to drive our son to the special school in Ballarat. that means if we don't get the funding to do so we will be forced to enroll him in the local mainstream school. The cost to the department to meet his needs at the most basic level will be huge. Yet a bean counter has been told to reduce the transport budget. So rather than shell out $20,000 in tranport. they will have to buy hoists, change tables, employ a full time medically trained aid, remodel the school for wheel chair accesibility (which is on a hill (have fun with that one)) and extra training existing staff. Since they won't be able to deal with him medically when he has an episode (unlike the special school) every time an ambulance will be called and he will be admitted to the Ballarat Base hospital further increasing the expense to the public purse via the health budget.

[quote="MacGyver"][quote="timmy"]what chemicals are you concerned about though?

i had a system running for 5 years with pvc pipe, and i had the produce professionally tested in a lab for organochlorine, organophosphate, PCB and 8 heavy metals and nothing but zinc showed up above the limits of detection at 0.001 mg/kg.

the zinc was 0.05 mg/kg, so you'd need to eat 2 kg's just to get the RDI.

it'd be interesting joel or someone went further with this and did some more extensive testing, it might put the concerns about pvc to bed once and for all.[/quote]

Do you use regular PVC or pressure PVC timmy?[/quote]

I just use normal PVC from bunnings or byap if i'm in the area.

Stuart, thank you for your reply and for voicing your opinions. My response was just a bit of fun as I am sure your tree hugging, commie, hippie remark was just a bit of fun.

I'm not a tree hugger but I think there is an issue with humans cutting down too many trees. Locally there are problems with once fertile land that is now affected by salt.

Much respect to you Stuart. I just found it humorous to juxtapose two extreme views.

I must also mention that show was also for fun but raised some interesting questions. Alex P Keaton was an aspiring capitalist business man with hippie parents.

Thanks timmy for your reply.

No worries Mac. I am a tree hugger just not a commie.

The thing is though that I apply the same logic as to my economic views to my environmental. I live next to/in the Wombat State Forest in Central Victoria. 150 years ago there was NO FOREST because every single stick had been cut down in the rape, burn and pillage that was the central Victorian gold rush. Every tree with only a handful of exceptions is regrowth and for decades the public forest and many private forests were managed sustainably. Then the government made a few stupid management decisions* and the environmental movement managed to have the whole forest shut down for commercial saw log operations and many of the private forests were clear felled and sown to pasture before the new rules came into effect. Ostensibly to ensure the protection of vulnerable species that had miraculously survived the complete vegetative removal of the gold rush and the 100+ years of sustainable forestry. What it was however, was merely "Not in my back yard" environmentalism. Since we still need forestry products those products now come, in part, from truly old growth forests elsewhere in Australia and around the world.

Similarly there has been a gold mine proposed just down the road. Those same people have been orchestrating demonstrations against the mine and have been using various products of our society that require gold to conduct their activities (mobile phones, computers, cars, etc.). Since the gold around here apparently can not be mined that means that there is greater motivation for mining companies to develop mines in Indonesia, Sumatra and the like without a skerick of environmental regulation. Personally I would rather they were just down the road subjected to all the regulations of our state, were I and those hypocrites can keep an eye on them.

* massive clear felling operations for wood chip that displaced local contractors

If tree hugger is slang for caring for the environment then that is what I am but I'm also aware that I'm living in suburbia, a place that was once occupied by trees. Conservation is important in my opinion.