Tuesday, July 14, 2009

The Great Greywater Debate- PVC or Polyethylene?

PVC v. Polyethylene

Homegrown Neighbor here. I've been wanting a greywater system for a long time. My old house does not exactly make access to the pipes easy, so I'm starting with just the washing machine. The neighbor, Mr. Homegrown, is anxious to try out a new design from Oasis.

So we have been trying to get all the pieces and get it done- and here is where we get stuck. The system can either use polyethylene tubing or pvc. PVC is ubiquitous, cheap and toxic. Just how toxic, I don't know exactly, but I've never chewed on any pieces just to be on the safe side. PVC is toxic to manufacture as well. This makes polyethylene the more ecological approach. But it is very hard to find in the size we need for the greywater system. And you have to buy a minimum amount- about 250 feet is the smallest we have found so far. For my yard, we probably only need about 40 feet. Plus, you have to mail order it. If we go the pvc route, it would cost far less and we could buy all the pieces at the local hardware store. We also want the system to be replicable so that we can share it with others and encourage them to use greywater. Searching for the parts for the polyethylene version is confusing - pvc is easy and accessible. This is the challenge. So what do people think- should we go with pvc or polyethylene?

Mr. Homegrown here. So I just found a local source for 1-inch polyethylene: Aqua-Flo. Cost is in the neighborhood of 33¢ a foot depending on how much you get. It comes in 20 foot and 100 foot lengths. So I think we're gonna go with polyethylene. Incidentally, when I called Aqua-Flo they asked if I was going to make hula hoops.

A correction and update 7/25/09: The Aqua-Flo branch I went to does not have black 1-inch HDPE tubing in stock. Other branches have it, but only in 500 foot rolls that cost over $300. A roll that long would make sense for a contractor, but for DIY greywater installations it ain't practical. Aqua-Flo does carry a new HDPE product called Blu-lock. You can get 1-inch Blu-lock in-100 foot rolls for a reasonable price (more info to follow in another post). Blu-lock uses special proprietary fittings that are easier to assemble than conventional mainline drip tubing and, intriguingly, allow for disassembly. I'm going to test Blu-lock and will report back on the results.
Posted by Homegrown Neighbor at 1:33 PM
Labels:

18 comments:

  1. If you go with the polyethylene, you can make hula hoops with the leftover tubing!

    http://www.jasonunbound.com/hoops.html
    ReplyDelete
  2. Vinyl in all its forms, inc. PVC, is definitely bad news. Good for you for not just using it by default for its convenience.

    Perhaps there are 5 other folks in your region of LA who have similar needs & would go in on the 250 ft length?
    ReplyDelete
  3. I would try a group purchase as Joe suggests, or take whatever I can find via Freecycle - at least that minimizes waste/unnecessary production.
    ReplyDelete
  4. True that PVC can be highly toxic during manufacturing and has caused severe health problems in the workers who make it, but as a finished product it is not particularly toxic (unless plasticizers have been added in order to make it flexible -- those leach). A lot of the workplace safety issues have been resolved, and there are very few new cases of the cancers caused by PVC as a result. There really isn't that much ecological difference between PVC and polyethylene as finished products. They're both plastics and they'll both still be here long, long, long after you're gone. So I say go with whatever is best for your project -- that way you minimize the risk that you'll be replacing the parts sometime soon.
    ReplyDelete
  5. Anonymous,

    Does the PVC that comes in 10 foot lengths at hardware stores have plasticizers in it? Or by flexible are we talking about stuff like PVC spa tubing?

    And thanks all for your opinions!
    ReplyDelete
  6. This post was made for me!
    PVC generally isn't toxic (true like Anonymous said) BUT, it can be toxic when it is exposed to UV light, then it degrades slowly and leeches.

    food grade Polyethylene tubing can be found in the kitchen section of your hardware store (because it's FDA approved), you can usually then get it by the foot so you won't have to purchase a minimum, (i got some to pump waste vegetable oil for my truck, and my mom used to own a frozen yogurt shop that used polyethylene tubes). This may not be UV resistant, but there are more size options.

    ALSO Most drip tubing is Polyethylene which you can by at the hardware store in 50 foot rolls, which I do regularly, home depot has 50 foot rolls. I would then use drip irrigation for adapters to get the right sizes. drip irrigation has sizes that are not akin to general irrigation sizes so because of that they make adapters. and most irrigation suppliers will sell it to you by the foot along with the adapters. There's a place in Upland I go to regularly called Modern Irrigation. Drip tubing is also UV light resistant

    Here's a link to home depot and a 50 ft roll of polyethylene drip tubing for 8 bucks.

    where the heck are you going that makes you buy 250 feet minimum? time to find a new hardware store
    ReplyDelete
  7. Hey Andrew,

    Thanks for your input, as always. Good to know about the UV problem. 1/2" polyethylene tubing is easy to find, but we need 1" tubing for this particular greywater application. Thankfully I found it at a irrigation supply place in smaller quantities.
    ReplyDelete
  8. PVC - would that be AKa "Pex" piping? I've been considering that for my 85 year old home plumbing replacements for the dying cast iron pipes...

    Look forward to seeing how this goes. Also any recommendations on cisterns? My rainbarrels are too inefficient for Oregon rains so I'm looking for a lower-cost cistern concept to incorporate until I have the $$ for a whole-house greywater system...

    LOVE the book btw...it's coffee table at mi casa...
    ReplyDelete
  9. EcoGrrl,

    Pex is polyethylene. I'd stick with copper if it were me. While I don't have a problem using polyethylene for outdoor irrigation, I'd be more conservative when it comes to indoor water supply lines. In addition to the potential dangers of ingesting plastic, I'm also suspicious of all novel building materials. They are often introduced in order to facilitate installation by unskilled labor. Best to go with materials that have stood the test of time (i.e. copper).

    As for cisterns, my friends in Petaluma picked up a big stock tank at agricultural supply place. They come in both plastic and metal. Ferrocement is another option if you've got a lot of time on your hands and a strong back!
    ReplyDelete
  10. I would be one of the reasons they asked you about the hula hoops.
    ReplyDelete
  11. didn't know you needed one inch. that explains it! good luck!
    ReplyDelete
  12. You could use the spare to make the hoops for netting plants or for making small to mid-sized polytunnels... (You've probably already thought of this!)
    ReplyDelete
  13. Did you ever consider glass pipe for this application? It is extremely strong and eco-friendly and fairly easy to install. Minimum size is 1-1/2" however. Google the word Kimax.
    ReplyDelete
  14. A correction and update 7/25/09: The Aqua-Flo branch I went to does not have black 1-inch HDPE tubing in stock. Other branches have it, but only in 500 foot rolls that cost over $300. A roll that long would make sense for a contractor, but for DIY greywater installations it ain't practical. Aqua-Flo does carry a new HDPE product called Blu-lock. You can get 1-inch Blu-lock in-100 foot rolls for a reasonable price (more info to follow in another post). Blu-lock uses special proprietary fittings that are easier to assemble than conventional mainline drip tubing and, intriguingly, allow for disassembly. I'm going to test Blu-lock and will report back on the results.
    ReplyDelete
  15. One other option not yet discussed is to use ABS pipe. ABS pipe is typically used for 'drain-waste-vent' applications - not pumped/pressure applications. Would be perfect for graity or low-pressure graywater systems. It does not contain any vinyl or chlorinated compounds. It is available at the local hardware store (black fittings & pipe) with all sorts of fittings available online if you need something more specialized. I'm not sure of its UV-resistance, but most of it will be buried anyways. This could be a good choice for runs of piping where you need a stiff pipe that is not susceptible to bending. For graywater applications (or anywhere you may have some solids/debris in the line), you will want to maintain a constant slope to drain with no dips in the line...that can be difficult with HDPE since it comes rolled up in a coil.
    ReplyDelete
  16. Try Ewing...lower price than aqua flow on 1" HDPE and they might sell it by the foot.
    ReplyDelete
  17. I'm surprised there's no discussion about which will hold up better. I've heard that PVC will hold up longer, but I've also heard that the poly is cool because you can make turns. Does anybody know how quickly or easily it will bust or cause problems? Also, will 1/2 inch blu-lock tubing have enough flow to supply an entire back yard full of sprinklers?
    ReplyDelete
  18. @Anon:

    The authors here. HDPE--Polyethylene--is much better from a health and environmental perspective, so now we use it as much as we can.

    Your question about the 1/2" tubing is hard to answer since we don't know how big your yard is or what your needs are. In general, you don't want to use greywater with sprinklers.
    ReplyDelete

Subscribe to: Post Comments (Atom)