Pool as Rainwater Storage Tank - Copper Sulfate

davidraubu

New member
Sep 26, 2013
4
San Jose, CA
Hello,

This is my first post here. I recently moved into a house with our first pool. I've been reading on chlorine alternatives. My motivation for this is very unusual. I have a dream of creating a completely self-sustaining home. One of the more difficult parts of such an endeavor would be rainwater storage, which would be mostly needed for growing food. I am investigating the feasibility of using a swimming pool as a rainwater storage tank. Hence, I do not necessarily require being able to swim in the pool, but just store water, and use it for growing food. There would be a second stage purification for indoor uses like drinking. Though being able to swim in the pool without chlorine, before dedicating it as rainwater storage, would be an added measure of confidence that the alternative disinfection is adequate.

I envision a pond liner covering the pool, then a removable wooden deck built over the lip of the pool, weighing down the pond liner. I think I have a rough design for such a deck that would cost like $1000 to $2000 to build. But perhaps I am naive. The pond liner and the deck would completely prevent debris, as well as make the pool into usable space. A hole can be punched in the center of the pond liner that allows rainwater to drain through the deck, and into the pool, through the hole. The gutters on the house would be rerouted to go through a sand filter or something, and then into the pool. The pool pump would be operated daily. The volume of water in the pool would vary, as water would be expended on agriculture, and we would depend on the annual rainfall to refill the pool. So the pump inlet would not be submerged all the time. So to pump the water, a hose would need to run from the pump inlet to the bottom of the deep end of the pool, and suck water from there.

I doubt plants would like being watered with chlorine, hence I ask about alternatives like copper sulfate (which would actually be good for plants in these amounts). The only downsides I have read about copper sulfate are potential staining of walls and hair. We have no blondes in the house and we swim minimally, and we would not swim at all if it were successfully converted to rainwater storage purposes. Also, I am not so concerned about purely cosmetic issues, especially since the pool walls are blue.

I have been messing around with some experiments of tap water in 4 gallon buckets in my back yard. I've tried a number of things, and here is what I have gleamed:

- Copper sulfate 500ppb has kept a bucket clear for 3 weeks. The buckets are in the shade 24/7. Still early in this experiment.
- Tap water control bucket is just starting to show the slightest signs of cloudiness after the same 3 weeks.
- Copper test strips measured about 500ppb copper at the start, then 1.5 weeks later it was down to about 200ppb, then today (3 weeks in) it measures about 400ppb. Strange that the copper decreased then increased. I tested multiple times on each occasion. Perhaps microorganisms are taking up the copper, and then liberating the copper at a later date?
- silver (1000ppb from silver citrate) by itself, and in combination with 500ppb copper, both did worse than the tap water control bucket, and got way cloudy.
- the triple combo of silver 1000ppb, copper 500ppb, and peroxide 30ppm, within a day, caused red tinted water, which I assumed was from peroxide having some reaction with the copper. And this bucket was the first to go cloudy of anything.
- previous experiments with silver citrate in concentrations as low as 10ppb, where the buckets were set in the sun, showed obviously longer time to develop algae than tap water control bucket. And none of them developed cloudiness like they did in the shade. (Evaporation in buckets that are in the sun is fast. So as you top them, you are increasing calcium and whatever else quite rapidly. That's why I thought it was better to test copper in the shade.)

So my overall question is: Is it feasible that a pool /rainwater tank can be maintained with only copper sulfate as the disinfectant? Are cosmetic reasons the only reason people don't seem to try this? I have read that copper works best if pH and calcium are kept low enough. Both of these are doable, and rainwater naturally has low ph and low calcium. In fact, I think much higher concentrations than 500ppb of copper can be soluble if pH is kept low enough.

I saw a youtube video where a guy managed his pool with copper sulfate and chlorine that was low enough to read 0. Though he did not say how sensitive his measurements were.

Okay, so here is where people smarter than I point out the flaws in my plan that are too many to number! I welcome them, and know I have a lot to learn.

Thank You,
David
 

tommyd123

Well-known member
Jun 28, 2013
90
Augusta, GA
I connot address your questions about the chemistry, but wouldnt the need to add copper sulfate on a regular basis negate the self sustaining part of your home? Also, if the "pool" were kept covered, that should prevent most algae growth. Just get a few plecostomus (plecostomi), the algae eating fish, they should take care of the algae growth.
 

davidraubu

New member
Sep 26, 2013
4
San Jose, CA
Thanks for the fish suggestion. An interesting idea. Though I don't know how fish do in the dark. The main reason for covering the pool would be for preventing evaporation.

I don't think anybody can go self-sufficient without initial investments of stocking certain materials. Copper sulfate would be cheap enough to stock a lifetime supply.
 

Isaac-1

TFP Expert
LifeTime Supporter
May 10, 2010
6,711
SW Louisiana
It seems to me a far simpler option would be to just cover and use chlorine (perhaps using an SWG (saltwater chlorine generators), the salt levels of around 3,000 ppm should be low enough to have no negative effect on plants. If your still concerned about chlorine in the water used to water plants, pump off from the main pool into a UV penetrable barrel and let the water sit there exposed to the sunlight for a few hours before using it , without any CYA in the water all the FC should quickly be burned off by the sunlight. Sure you would still have to replenish salt from time to time, but in bulk it is fairly cheap.

Ike

ps see a couple of links www.sebiology.org/publications/Bulletin ... inity.html?

http://www.salinitymanagement.org/Salin ... ochure.pdf
 

X-PertPool

TFP Expert
In The Industry
Jun 12, 2009
1,385
Exeter, PA
Hmm.. I personally think I would stick with chlorine or bromine since it kills much faster. Even if the water is clear doesn't mean it's safe. Anyways I would keep the pool on chlorine and then reduce the levels of chlorine by running it through an activated charcoal filter or some sort. For example a brewery uses city water for the most part and then gets rid of the chlorine out of that water. If you wanted to go without chlorine at all I would then do something along the lines of using this http://www.biotop-natural-pool.com/
 

danacc

LifeTime Supporter
Jun 29, 2013
269
When you use the pool to hold rainwater for watering crops, what are you trying to make sure it stays free of? Algae? Plant pathogens? Human pathogens? Other?

I don't think your bucket test is going to tell you if the water is safe for watering plants. There's nothing inherently unhealthy about watering plants with cloudy or algae-filled water. I would think the concern would be around plant pathogens, and maybe around human pathogens if you expect it to splash on the produce. You're going to need somebody smarter than me to say whether copper can do that for you. (You are correct that chlorine will not unless you raise the level to one that might cause distress to the plants.)

But don't worry about "cloudy". That's probably harmless algae.
 

4knights

LifeTime Supporter
Aug 19, 2012
431
NE Kansas
aldrichg9 said:
Correct me if I'm wrong but this sounds to me like a cistern
No need to over engineer what humans have been doing for thousands of years.
People have been catching and storing rain water since a few years before algaecides.
http://en.m.wikipedia.org/wiki/Cistern
Pretty much dig a well. Line it. And put a lid on it

Sounds like a cistern to me! My grandparents had only a rainwater cistern their whole lives(89/87yo) it is still in place but the new owners only use it for watering the yard and gardens.
 

aldrichg9

Active member
Sep 1, 2013
36
Terre Haute, IN
davidraubu said:
I don't think anybody can go self-sufficient without initial investments of stocking certain materials. Copper sulfate would be cheap enough to stock a lifetime supply.

See this depends on your reason for going self sufficient, but storing dry and canned goods(and copper sulfate) does not make a self sufficient home. IMHO of course
What if the chemicals are stolen?
I'm not saying these things to be argumentative, only wondering what it is that you are after.


In any case, :cheers: I live in a small town (3000) and there is one house I almost bought with a cistern under the garage.
Gutters were piped into it.
The well at the home did not produce sufficient amounts of water and some water needs had to be supplemented this way.
Never would have known it was there if the realtor had not mentioned it.
Another house I drive by on my way to work every day has a cistern in the front yard that they haul water to continuously. It's their only water source, however in this case they haul city water which is chlorinated.
 

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easttn

Well-known member
Jun 22, 2013
309
East TN
Ive been watering my plants with chlorinated city water for years. Never hurt mine. My city water measures 2 or 3 ppm of FC. I would say you could run more than that and be ok, but I wouldnt know where the limit would be. I dont know how you plan on irrigating but an algae bloom will surely clog up your emitters, drip line or filter.

I believe if it were me I would run chlorine in mine. You would be better off with an air gap between the liner and the pool to allow the CC to escape and to keep the temperature down in the summer instead of making it air tight.
 

Isaac-1

TFP Expert
LifeTime Supporter
May 10, 2010
6,711
SW Louisiana
Cisterns, are not without their own set of potential problems depending on the area their can be any number of them that could result in problems for the family, but a couple that come to mind in this application is they could become breeding grounds for dangerous bacteria what could spread to vegetables grown, washed, etc. with water from this pool, also they can become Mosquito breeding grounds. The best cisterns are going to be kept completely dark, and well screened, something that may be hard to do with a pool.
 

in-two

Well-known member
Nov 13, 2011
51
Sabina, Italy
I'd like to join in this conversation because I have both a pool and a large cistern and wonder about using them in conjunction with each other. My goals are not the noble ones of sustainability, just practicality and avoiding wasting water when I eventually drain my pool to do repairs and re-finishing. The cistern is a concrete box built into the side of a hill, essentially light proof and fed from a shallow well sunk just next to a small stream at the bottom of a steep valley. I'm guessing that the water source is mainly surface run-off but there is some evidence of an underground watercourse, following the same course as the stream. I have never tested this water but suspect it will have at least some chemical and natural fertiliser in from our surrounding farms, and may well have some human waste in it as this area has no sewer system, just septic tanks etc. The water is clean and clear when it comes out of the stream and smells and tastes o.k. but I only use it for irrigation through an extensive sprinkler system. I have used it to top up the pool but this has coincided with getting an algae bloom (not necessarily causal but enough of a PITA to not try it again). So my questions:

1/ How/where can I test this water, and most importantly, what do I test it for to see if it is o.k. to use in the pool?
2/ If I drain my chlorinated pool water (lets say 5ppm FCL) into the cistern (previously mostly emptied) will I have a problem with using some of this water for irrigation i.e. is it likely to harm flowers/plants/grass/shrubs/vegetables while I work on the pool re-furb?
3/ Will it be O.K. to refill the pool from the cistern, which is the basic idea, and what treatment should/could I give the water
while it is still in the cistern before it goes in the pool?

I appreciate that almost every thing depends on what is actually in the cistern water but I would love to hear from TFPers who have had similar issues, which are very close to the O P 's, and if there are any serious chemistry/biology issues to look out for (Chem Geek we love you....!)

Thanks for listening...
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
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In The Industry
Apr 1, 2007
34,517
Sebring, Florida
Lot of interest in this thread but it belongs in The Deep End forum, so I am moving it there.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
davidraubu said:
- Copper sulfate 500ppb has kept a bucket clear for 3 weeks. The buckets are in the shade 24/7. Still early in this experiment.
- Tap water control bucket is just starting to show the slightest signs of cloudiness after the same 3 weeks.
- Copper test strips measured about 500ppb copper at the start, then 1.5 weeks later it was down to about 200ppb, then today (3 weeks in) it measures about 400ppb. Strange that the copper decreased then increased. I tested multiple times on each occasion. Perhaps microorganisms are taking up the copper, and then liberating the copper at a later date?
- silver (1000ppb from silver citrate) by itself, and in combination with 500ppb copper, both did worse than the tap water control bucket, and got way cloudy.
- the triple combo of silver 1000ppb, copper 500ppb, and peroxide 30ppm, within a day, caused red tinted water, which I assumed was from peroxide having some reaction with the copper. And this bucket was the first to go cloudy of anything.
- previous experiments with silver citrate in concentrations as low as 10ppb, where the buckets were set in the sun, showed obviously longer time to develop algae than tap water control bucket. And none of them developed cloudiness like they did in the shade. (Evaporation in buckets that are in the sun is fast. So as you top them, you are increasing calcium and whatever else quite rapidly. That's why I thought it was better to test copper in the shade.)
If you just looked at the results of your tests you would see that they aren't very reliable for making conclusions. Why did you use 1000 ppb silver since normally you use around 20 ppb? Also having the silver with copper should have been at least as good as with copper alone unless the silver was so high that with higher pH it was precipitating causing cloudiness (that's quite possible). Your copper concentration differences just show how ridiculously inaccurate test strips are. Also, if you really want to test prevention of algae, you should increase the algae nutrients (phosphates and nitrates, so essentially fertilizer) level in your test water.

Are you aware that copper kills algae and that alage is closely related to plants? It is an essential nutrient needed at low levels, but at higher levels it kills plants. The copper at the levels you indicate will be far worse than the chlorine if kept at reasonable levels.

As others have noted, collecting rain water in cisterns is the usual approach and can be subsequently treated as needed to kill microorganisms.
 

davidraubu

New member
Sep 26, 2013
4
San Jose, CA
Thanks for all the replies. Some comments:

- My idea with sustainability is not just for myself, but doing something that people can reproduce. In my opinion, the country is going to need this type of stuff sooner or later. Many people already have pools, but not many have cisterns, and buying some small cisterns or barrels may not support sufficient agriculture for a family. And even those can be expensive. So the challenge of redeploying a pool is what I hope to achieve, as that would be of practical benefit to the most people.

- I have seen a company that turns pools into cisterns with a well on top of it, but that would not be cheap and easily reproducible, and I want to shoot as close to the moon as possible. Covering a pool, as described previously, with a pond liner and a removable deck would virtually eliminate debris, light, and evaporation for a reasonable startup cost.

- Making the pool continue to function as a usable pool could avoid potential problems with satisfying rules and regulations about storing rainwater, of which I have yet to learn much. Hey, it's still just a fully functional pool in my backyard after all, right? I just happen to refill it with rainwater, keep it covered all the time, and dump in on my crops. No need to get any kind of permits, except possibly for the deck. So in these senses, this whole pool idea lends itself to easier reproducibility. Though the deck is really optional, only if you want the pool area as usable space. The pool at minimum just needs to have no evaporation, and to continue to operate as something that you could remove the covering and swim in, for as little cost as possible.

- Great idea with the UV penetrable barrel. Never thought of that. Though I would like to explore something like copper sulfate, which if it were found to be sufficient, would require virtually no cost as compared to chlorine.

- Regarding the concept of sustainability - There really is no such thing as absolute sustainability. For example, starting with 4 walls and a roof over your head is cheating in a sense. But everyone has to start with something, and stock some things. Definitely food needs to be produced year round. Ya, storing cans is out. In my opinion, something like copper sulfate that you can get 3 lbs for $8 and have it last a couple decades is an acceptable item to stock while still being in the spirit of sustainability. I envision sustainable communities, where first off, people wouldn't steal from one another. But if someone stole my copper sulfate, other people would have plenty to spare me.

- I hadn't realized copper titration kits were available before I bought the copper strips. Though I did measure with the strips 3 times at each interval, and the measurements were consistent, which is what bothers me. Though perhaps it was just a fluke. Also these particular strips always measure 0 if silver is also in a bucket. Only good for a copper only bucket.

- Ya, I know my bucket experiments don't tell me much. Never said they did. Just disclosing the data I have so far. More rounds of experiments to come. Now I have more ideas about what and how to test.

- Up to 70ppb silver from silver citrate was not sufficient to prevent algae growth in buckets kept in the sun in a previous experiment I did. I figured in this round of experiments I would just go as high as I would conceivable be willing to put in a pool, and that I would then scale down the amount of copper and silver in future rounds of experiments. Intentional overkill. But now I look and see the solubility of silver citrate in water is only 285 ppm, so the cloudiness I saw was probably silver and not algae. Oops, overlooked the obvious. That would make sense, as I was really bummed out not understanding how the copper by itself could outperform the combination.

- I had done some research and concluded that watering plants with copper in this concentration would actually be in the beneficial range. Silver is also very useful for treating plant diseases (and human diseases for that matter)

Thanks All,
David
 

Shane1

LifeTime Supporter
Apr 29, 2010
621
Buckeye, AZ 85326
I think what you are trying to do is pretty cool so good luck with it. I've never seen any data that states chlorine is bad for plants....but I've never looked for it. For about 10 years my dad watered his lawn and garden with his backwash water and always had a good produce. If I were researching this project I would want to know the short and long term effects of chlorine on plant and soil life. Then start solving the problems if there are any.
 

Patrick_B

TFP Expert
LifeTime Supporter
Jun 7, 2011
15,006
Midland TX
I'm going to answer in a crudely simple way. I am a bleach freak, and use it in washing out ice chests, Hummingbird feeders and all sorts of things around back yard activities like cookouts and such. I know for a fact that the FC levels in these items are at least many hundreds of times the levels of FC you ever see in a pool or drinking water. I pour them straight on the lawn or flower beds when I'm done and have yet to see ill effects. I cannot imagine the amounts needed to sanitize drinking water would ever hurt any vegetable plant. FC is consumed so quickly in soil it simply wont matter.
 

davidraubu

New member
Sep 26, 2013
4
San Jose, CA
oops, got ppm and ppb mixed up. 285ppm solubility of silver from citrate ought to have been more than enough to accommodate 1000ppb silver from silver citrate. So the murkiness is still mysterious. Will do more experiments.
 

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