Hi Everyone, nice to bump in to a group of like minded locals. Please forgive my over-excitedness and general noob cluelessness :-)Does anyone know of any work that has been done on using functioning swimming pools as storage for rain water and grey water to be used in irrigation? Its seemed to me for some time that there must be a way to integrate these systems. It seems like many of the issues surrounding grey water and rain water irrigation are related to being able to safely store it so that it can be dosed out over time. This has challenges related to storage capacity and and cleanliness. Meanwhile, many people in this hot climate have a very large 20-30,000 gallon storage container sitting in their back yard with its own filtration and purification system built in :-)The chemicals (chlorine or salt) needed to keep a pool clean seem like one of the biggest obstacles, which led me to look into copper based pool cleaning systems like these:http://www.clfree.com/index1.htmhttp://www.ecosmarte.com/If these systems do what they advertise, it would seem like they could solve any issues of pool chemicals harming your plants or the local eco-system.It seems like adding collected rainwater to your pool system should be fairly straight forward, although you'd probably need to keep an eye on pH after a big rain. I suppose you would also have to do some amount of filtering to get out any junk it picks up on the roof. Grey water seems like the bigger challenge to me. Having no first hand knowledge of grey water, I'm having trouble gaging how much processing it would likely need before it could be added to the pool without turning it into a soapy dirty grimy mess. Would running it through something like a sand filter (maybe even the same one the pool uses) likely be sufficient, or would it likely require some sort of pond/wetland system to get it clean enough?In addition to providing you a way to store and clean your rain/grey water it would seem to me like a system of this nature would in general improve the green-ness of pools, which lets face it are pretty un-green. At least in a system like this you should be able to stop filling up the pool with drinking water to replace evaporated water. I would also think that moving from a strictly closed loop system, where all the minerals left behind by evaporation are stuck in the pool, to an open loop system, where water is continually drained from (for irrigation) and added to (hopefully mostly from grey/rain water sources) would reduce or eliminate the need to drain and refill the pool due to hardness of the water. This could potentially save 20-30,000 gallons every 5-7 years, and eliminated the related chlorine release into the local environment.Anyone have any thoughts or resources on this sort of thing you could point me towards? (general resources/comments are great, but ones specific to integrating pools with grey and/or rain water and irrigation would be awesome!) Also anyone who knows anything about salt/chlorine free pool systems I'd love to hear how they work!Thanks,Rob
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That's one of the biggest hurdles to rainwater harvesting in Phoenix, Chris - water is so artificially inexpensive here. However, I've heard that rates will be going up soon. The City of Phoenix is considering a tiered system like the one used in Tucson, where the first few units (100 cubic feet or 748 gallons) will cost the same, but after that, the price per unit goes up with increasing usage. In a tiered pay system, a rainwater harvesting system can ensure that you don't get into the higher-costing usage brackets. And, of course, for every unit of water you don't buy from the city, you don't have to pay sewer fees for that unit - which saves even more money. Perhaps then it will make rainwater harvesting more popular, because then there will be an actual return on investment within one's lifetime.
Also, as far as reducing evaporation from a storage device goes - a closed tank will also eliminate algae growth and mosquitoes without the use of chemicals. And when you're talking rainwater harvesting - you're really talking about two things: conservation and water quality. If we could add "savings" to that, it could very well take off here in the Valley; like it has in Tucson, Prescott, and Flagstaff.
I'm going to attack this from a slightly different perspective than Chris, and perhaps different from what you've asked, Rob.
In any active rainwater harvesting system, you have 5 basic components:
1. Catchment area (roof)
2. Conveyance system (gutters)
3. Filter / First flush device
4. Storage (usually a tank)
5. Distribution system (garden hose or pump & existing irrigation system)
Even if you want to use your pool for storage, you still need the other components. Also realize that if you convey the rainwater directly into your pool - even with a fairly effective first-flush device - you'll have microscopic pieces of bird poop and other contaminants in your pool, and you are very limited as to how much rainwater can go into your pool - what happens if it's already full from a monsoon storm a day or two ago? You will also need some kind of submersible pump to distribute the water for irrigation (unless you planned on scooping it out by the bucketful, or flood-irrigating when you backwash). So, really - the only component you're replacing as opposed to a conventional active rainwater harvesting system is the tank, which, admittedly, can be a big investment - especially if you don't make the common mistake of undersizing your system. We lose 80-100 inches a year to evaporation here, so a pool with an average depth of 4 feet can lose up to twice its volume in a year. If your pool is 15,000 gallons, that's 30,000 gallons right there, before you've irrigated a single plant. That is beyond what most homes can collect in a single year. Even a 3,000 s.f. roof can only collect up to about 14,000 gallons in our average 8" of rainfall per year here. An average house with 2,000 s.f. of roof can collect a bit less than 10,000 gallons. That's why a pool cover is a very cost-effective investment here (Of course, a 15' x 30' pool will itself collect about 2,160 gallons of rain per year)
My advice would be to install a system that is large enough to handle your water needs year-round - space and HOA permitting, of course. A realistic volume for a rainwater harvesting tank that will get you through the dry spells of April-June (maybe - depending on your needs) and the semi-dry months of Sep-Nov is around 3,000 gallons. Collecting your rainwater in tanks allows the sediments and organic contaminants to settle to the bottom of the tank; the water is ideally distributed from the cleanest area - a few inches below the surface. The outlet from your tank can go to both the float valve on your pool and to a pump connected to your irrigation system (or a garden hose).
Now - that being said - any size tank is better than no tank at all. But it's silly to spend thousands of dollars on gutters and a pump and only have 55 gallons of rainwater available a few times a year.
I might add that using your pool filter pump to push water thru your irrigation system is not a good idea - for many reasons.
Greywater should go directly onto the soil of whatever plants you want to irrigate - but not in your garden. Nothing you eat should be watered with greywater except for fruit trees. Also, greywater should never be stored - there are too many organic contaminants for safe storage, unless, as Chris pointed out, you're willing to spend a fortune on filters and chemicals.
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Also, as far as reducing evaporation from a storage device goes - a closed tank will also eliminate algae growth and mosquitoes without the use of chemicals. And when you're talking rainwater harvesting - you're really talking about two things: conservation and water quality. If we could add "savings" to that, it could very well take off here in the Valley; like it has in Tucson, Prescott, and Flagstaff.
In any active rainwater harvesting system, you have 5 basic components:
1. Catchment area (roof)
2. Conveyance system (gutters)
3. Filter / First flush device
4. Storage (usually a tank)
5. Distribution system (garden hose or pump & existing irrigation system)
Even if you want to use your pool for storage, you still need the other components. Also realize that if you convey the rainwater directly into your pool - even with a fairly effective first-flush device - you'll have microscopic pieces of bird poop and other contaminants in your pool, and you are very limited as to how much rainwater can go into your pool - what happens if it's already full from a monsoon storm a day or two ago? You will also need some kind of submersible pump to distribute the water for irrigation (unless you planned on scooping it out by the bucketful, or flood-irrigating when you backwash). So, really - the only component you're replacing as opposed to a conventional active rainwater harvesting system is the tank, which, admittedly, can be a big investment - especially if you don't make the common mistake of undersizing your system. We lose 80-100 inches a year to evaporation here, so a pool with an average depth of 4 feet can lose up to twice its volume in a year. If your pool is 15,000 gallons, that's 30,000 gallons right there, before you've irrigated a single plant. That is beyond what most homes can collect in a single year. Even a 3,000 s.f. roof can only collect up to about 14,000 gallons in our average 8" of rainfall per year here. An average house with 2,000 s.f. of roof can collect a bit less than 10,000 gallons. That's why a pool cover is a very cost-effective investment here (Of course, a 15' x 30' pool will itself collect about 2,160 gallons of rain per year)
My advice would be to install a system that is large enough to handle your water needs year-round - space and HOA permitting, of course. A realistic volume for a rainwater harvesting tank that will get you through the dry spells of April-June (maybe - depending on your needs) and the semi-dry months of Sep-Nov is around 3,000 gallons. Collecting your rainwater in tanks allows the sediments and organic contaminants to settle to the bottom of the tank; the water is ideally distributed from the cleanest area - a few inches below the surface. The outlet from your tank can go to both the float valve on your pool and to a pump connected to your irrigation system (or a garden hose).
Now - that being said - any size tank is better than no tank at all. But it's silly to spend thousands of dollars on gutters and a pump and only have 55 gallons of rainwater available a few times a year.
I might add that using your pool filter pump to push water thru your irrigation system is not a good idea - for many reasons.
Greywater should go directly onto the soil of whatever plants you want to irrigate - but not in your garden. Nothing you eat should be watered with greywater except for fruit trees. Also, greywater should never be stored - there are too many organic contaminants for safe storage, unless, as Chris pointed out, you're willing to spend a fortune on filters and chemicals.
Good luck,
-Jeff-