Greywater nontoxic piping options

Thanks for visiting the forums Laura! There are a number of people who are concerned about the use of plastics in systems that will feed back into food. In your experience, what are some other options that could reduce system water's contact with materials that may be putting things harmful to humans or other species in the system?

Stainless steel maybe? Or copper?

Hi Caleb,

I share the general concern about plastics, however from a slightly different angle.

Not all plastics are the same: You can install a greywater system, like the laundry-to-landscape system, using HDPE (high density polyethylene) which is a more benign type of plastic than PVC- a more toxic variety.
Gravity flow systems can use ABS instead of PVC.

It's hard to totally avoid plastic nowadays: In our social context, where drinking water often is plumbed in plastic, food is packaged in plastic, most people drink or eat out of plastic (at least on occasion), using plastic pipes in a greywater system is a very small amount of potential exposure through the food system compared to these other ways. If the greywater pipes are kept of out of the sun and the water is inside the pipe a short amount of time (it's just flowing through) little chemicals would be leached out. I do not know about the fate of chemical compounds that leach from plastic entering an aerobic soil environment or how much they may be absorbed by plants, but I assume the amount is negligible compared with using plastic directly with drinking water, like drinking out of a plastic cup in a restaurant. Also, most any irrigation systems or hoses we use to irrigate contains plastics or other potentially harmful materials.

Making plastic is toxic: From my perspective, the main issue with using plastic in a greywater system lies in the problems with manufacturing plastic. Making plastic, particularly PVC, is a toxic and environmentally destructive industry. The manufacturing plants are very harmful to the health of people who live near them, an environmental justice issue. We should try to minimize and avoid plastic, PVC in particular, as much as we can. Some of this can be done with the design of the system, by locating plants to be irrigated with greywater as close to the greywater source as possible.

Perhaps bamboo: Unfortunately using metal pipe in a greywater system is not practical for most people. It's expensive and harder to work with. If anyone has metal pipe made for water it would be fine to try to reuse it though. I think the most practical option is using the less-bad types of plastics, like HDPE. Or perhaps using bamboo. I haven't done it myself, but bamboo has been used for water pipes around the world, though the longevity won't be as long as with plastic or metals. I'd love to hear from people who've tried using bamboo for greywater piping.

No pipe options: Art Ludwig has a good alternative to pipe for rural situations (definitely not up to any US code), using cement lined trenches that branch water to plants. I did a quick image search and couldn't find it on-line, but there are images in his book "Create an Oasis with Greywater".

The following Non-Toxic piping option ideas are best suited for exterior locations.

Clay Pipe

Vitrified clay sewer pipe webpage or clay drainage tiles could be used. You may be able to find used clay drainage tiles, often used in agricultural areas and older home sewer connections. It will most likely be found in larger diameters than required but should be fine by including provisional cleanout locations and installing with adequate slope. Ceramic flue liners may provide a useable substitution.




Bottle Pipe

I have an idea to use wine or beer bottles to make pipe. Cut both bottom and top (a few inches into the neck) off of the bottle. The tapered end of one bottle could fit into the bottom of the next "downhill" bottle. I think the "bottle pipe" could be made above grade or buried through the garden with slight curves possible, providing appropriate slope. Small amounts of leakage from imperfect joints would be negligable provided installation exterior of the home.

Used Clay or ceramic vases, pots or other could also be modified in a similar fashion.


Ground Channel or Gutter Options

Clay roofing tiles could be used by installing them to make a "ground gutter", similar to the concrete gutter mentioned in the above post

Bricks could be used to make a "u" shaped channel by lining the base and creating sides with the brick - ongoing maintenance would likely be required

The tops of the channels could be left open or covered with a removable cover depending on location and aesthetic requirements

Sh.. I have already bought pvc, and I knew this of the chlore inside, but I did not know what else.
I guess HDPE is the ordinary black pipe for watering gardens?
Then I can see another advantage to it, it is a little bit flexible, for some slght curves.
The drawback is the price, and I would have thought that they were more expansive because of the higher cost of energy to make them.

To avoid plastic, I would recommend cast iron (ASTM A74) DWV piping. It can expensive.

Don't use steel or copper piping, since drainage piping "breathes" and will result in corrosion.

As far as "less bad" PVC, be sure it is certified NSF Standard 61 compliant. This standard ensures that the plastic is rated for potable water with minimal leeching. Note that typical DWV PVC will not be rated per NSF 61.

For exterior applications, a classic french drain would work well. 1) Dig a trench 2) line with impervious material (clay) 3) backfill with coarse gravel.

Those are my 2-cents as an engineer.