Harvested rainwater for non potable use in the home
 

I am a technical writer/engineer at a small company that does contract engineering.
i.e.; people come to us with an idea and ask us to make it work.

Technical Services

Our field of expertise is electronic engine controls. We work a lot with MEFI controllers. But that's off topic.

Just the other day the boss dropped a new project in my lap. The concept is to use harvested rainwater to flush toilets.
Have any of you guys seen any technologies that interface a rainwater system with a city water (or well water) supply?
I've been internet surfing like mad, and have found some sites like harvesth2o.com and others that are linked from threads here on ecorenovator, but have not found much yet.

I just don't want to be reinventing the wheel. :p

It's definitely a good idea; grey water systems turn black and are gross to see sitting in the toilet; rainwater seems to be an excellent choice.
Hope to hear someone's used it already. good luck.

Sorry, I don't know anything about it (yet). If you come up with anything you can share, please do!

I haven't seen anything about this type of setup specifically... but...

When I grew up I lived on a farm... it was once a very old farm and there was a wind mill that actually did the water pumping. We had a big cistern that held the water that was pumped so you had it on windless days... kind of like a battery bank I suppose. Something like that may be a good place to start. I would put a second water holding tank in the attic (provided it wouldn't freeze) to allow gravity feeding of water to the toilets. Use a small pump to get water from the cistern to the attic, let gravity do the rest.

Where I live now, one section of our roof drains at one point (we don't have gutters) and we can fill one garbage can with water if there is a good rain. I use it to water the plants when it's dry.

Yup, seems that "Everything old is new again".

I've been surprised how widespread 'rainwater harvesting' is around the globe. It's even a required design element for new construction in Bermuda and the Virgin Islands.

It's such a simple concept. Now I want to install a system at my house... :p

Thanks for the input, wyatt. The attic tank is a good idea...

Rainwater is naturally soft, but corrosive to metal plumbing. PVC and PEX are recommended.

What am I gonna make the valving out of? $tainless? Injection-molded plastic? Hmmm...

Not to throw your thread out of whack....but what's the difference between PVC and ABS plumbing? I'm doing the tomato plant thing in the other thread...and it's asking for PVC pipe to fill the tub with water, I guess because it can take the rain water. I have Schedule 40 ABS pipe...that's not the same thing is it?

Higgy,
I am guessing he used PVC because he could find it easily (one of his criteria). Rain water isn't going to hurt plastic (hopefully). Not sure on the differences.
Tango Charlie,
What kind of valving are you in need of? I would think you could find PVC plumbing valves that would do the job quite nicely. I have seen PVC ball valves for simple "ON/OFF" operation. Do you need something more sophisticated? A major advantage of using what exists is that you don't have to make it yourself.

Well, the goal is to meter in rainwater with the city water going to the toilet, in varying proportions. During a drought, more city water will need to be used, to prevent exhausting the cistern, and to keep things flushing smoothly. :)

That's what I was looking to see if anything was already out there, commercially or otherwise. Haven't found anything, so it looks like we'll be doing this from a clean sheet of paper, as they say. I'm thinking it'll take some sort of actuated valve that will interface the two systems. And it must be automatic, so the homeowner doesn't have to fiddle with it. Initially, it'll probably be used in a 'smart house' that's all wired up into a computer. But we'd also like to make it a stand alone system that can be retrofitted into any house.

I'm learning A LOT on this project. Let me research ABS vs. PVC. I don't think rainwater affects either. It's the metal piping that's the problem, because of corrosion.

Thanks for the feedback, guys!

I would think you would want to keep your cistern cycling so the water doesn't have time to stand and start growing things, so what I would suggest (with nothing to back me up) is that the cistern gets used for flushing the toilets 100% until it's depleted to maybe 10% of capacity. At this point you can have a float in the cistern (an existing technology) that will be tripped and keep the cistern from going completely dry, but also keep it from going completely stagnant. This would make it a stand alone system and make it so there can be computer monitoring, but the computer is out of the loop for all intents and purposes.