As a novice to all of this, I continue to have questions. The system I'm building is flood and drain with a 500 gallon fish tank with a 1:1 grow bed ratio. First, I'm planning on using 1/2" delivery pipe and 1" drain pipe. The 1/2" was based upon the recommendation in Sylvia's book. Also, per her book, I'm planning to not cement any of the joints. This part especially concerns me. Any thoughts on either of these two points would be appreciated.
Except that Pex needs to be protected from sunlight and other UV light or it degrades. There is a reason they don't use Pex for irrigation.
Many of the fittings require special tools.
Also, Pex is rather expensive when you get into the Large sizes. I don't think I've ever seen anything bigger than 1" at Lowes around here and it is usually far smaller. My AP systems generally use mostly larger than 1" pipe and only go smaller to send sprays into the towers. Now if you could show me that 1 1/2" and 3" and 4" pex will work with uniseals and the cost of the Pex, fittings and something to protect the Pex from the sun wouldn't cost more than say 4X as much as the PVC, then maybe it would be worth looking into.
As to the potential contaminates, There have been cases of contaminates leaching from PEX and if you are using new regular white rigid PVC for plumbing then the risks of contamination from that is about the same as PEX.
Where PVC is a NASTY has to do with it's manufacturing and it's disposal. The manufacturing of PVC uses lots of chlorine and can produce pollution, some nasty pollution. And if you are burning your pipes for some odd reason, then I don't recommend using PVC since if you burn it at the wrong temperatures you can be giving off some nasty stuff then too. However I don't think most of us are setting flame to our plastic plumbing in order to heat our system water nor burning it to heat the greenhouse.
That said, it is the flexible PVC that contains plasticizers that can leach not so savory stuff into our systems. So I don't recommend the heavy use of the flexible PVC hoses or vinyl liners even though some of them are "potable water or food grade" they still leach some of those plasticizers that have been linked to hormone disruption and other things.
If you pump water into a closed ended pipe the pressure would build up and blow out your joints. Hower you are not useing that type system and the water keeps flowing and there is no presure to be concerned with. Just tap them tight and go.
Good luck charles Sargent
While most aquaponics set ups may use only minimal pressure so often tapping them tight may be enough to avoid things coming apart, I've seen blow outs that managed to loose a lot of water from a system in a very short time so I'm cautious about telling people not to glue things. There are dangers in non-glued plumbing.
I love the idea of PEX. I have used it on new homes for the last 10 years and think it's an amazing product. I assume you use a large diameter. I actually use Wirsbo and the flaring tool only goes up to 1". How is the pex working out for you after 1 year?
Bob Rogers aka The White Lion said:
I would also look into using PEX Pipe for plumbing your system. It is very flexible and the fittings do not use any glue. Once you have made your connections and tightened the fittings, you will never experience any leaks. You can also use the different colors to distinguish your different water flows. One color for the outflow and one color for the inflow or return line. Its great stuff to use and very easy to work with, with the added plus of not having any potential contaminates.
Pex doesn't stand up to UV so you have to protect it from the light. And in my experience most easily available PEX isn't going to be big enough for anything but the smallest of systems and definitely not big enough for gravity flow plumbing.