Rainwater harvesting system design


Old 12-01-13, 04:50 AM
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Rainwater harvesting system design

I'm including a rainwater harvesting system in my bed and breakfast. The design will include a cistern outside the building and a well tank and pump in the basement. The rainwater will be used for toilet flushing and laundry.

I'll need a city water supply line for back-up when the tank drawdown exceeds demand or during the winter months when precipitation is frozen.

What sort of special considerations are there for the piping from the cistern to the well tank? How can I automate the switch from cistern to city water/city pressure? Can I avoid a well pump and use the city ores sure to power the rainwater in the line? Any other advice out there from experienced rainwater harvesters?
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Old 12-01-13, 05:43 AM
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Since you will be involving the plumbing inside the building and tying both the reclaimed and municipal water supplies together you should first talk with your local building inspections dept. Make sure they are comfortable with, and will approve a non-standard system. In my town non-standard stuff is often met with a "no" or "you must provide me with all the information needed to show that it meets the code..." They will approve unusual things but they often push the burden of proof back to the homeowner/builder. Reclaimed systems are becoming more popular so you should have an easier time than if you attempted this 10 or 15 years ago.

I don't think powering your reclaimed system with city water is a smart option. The pump will be consuming and wasting city water to power the pump which will negate any benefit from having a reclaimed water system.

What you want can be done. Here are a few things I think you might need:
A check valve on each system to prevent the water from one system backflowing into the other. A pressure reducing valve on the municipal supply to limit it's pressure to close to the reclaimed's pump presure.
A pump, pressure tank and pressure switch on the reclaimed system.
A float switch in the cistern to turn off the pump when the water level is low. This switch can also activate a valve allowing city water to take over.
Old 12-01-13, 08:48 AM
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It might be easier to use the city water to refill your cistern when it is too low.

Here are the rain harvesting links I have. I got them a few years ago so I don't know what exact info they can provide. I remember reading a publication put out by the Texas state government. I don't seem to have it bookmarked. Texas seemed to be very encouraging in building these types of systems. So you may find some more info there as well.

RainHarvest Systems | Rainwater Collection Systems for Harvesting Rainwater
American Rainwater Catchment Systems Association
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