rainwater, swimming pool, irrigation cistern

Within the next couple of years, I am going to want to have a small above ground pool. This pool will be located approximately 8 degrees from the equator, so, no need to ever heat it with anything other than solar energy.

This idea started with the idea that I will need rainwater catchment and and an irrigation water storage tank. I don't want to store water seasonally, but instead, just store a few thousand gallons at a time, whether it is pumped from a shallow well or it comes off the roof. This water will be used for swimming during the first few days after it is filled. I won't purchase any chemical to keep it fresh. Moringa and Neem grow quite well in the Philippine Islands, and when added to water, both help to clarify and make it unsuitable for mosquito larvae. They use Moringa seeds which contain an antiseptic oil, to purify drinking water.

 I did some bathing while I was there, just by standing under the downspout when it rained. I got nice and clean, using the soap that we manufactured. We went swimming in a couple very clean rivers, after questioning locals about the existence of any nasty creepy crawlies, ranging from leeches to saltwater crocs. The water there doesn't seem to have any adverse effect on me. My fiance has been swimming in it all of her life.

This water won't be piped into drip irrigation or any other small tubing that could clog. Instead, it will be used to irrigate big trenches that are filled with bananas, moringa, luceana and other things that benefit from periodic flood irrigation. I'm searching in places that have high water tables, so run off losses aren't really lost. I expect to run it through 2-inch pipe that is moved to wherever water is needed.
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Concrete blocks cost roughly $0.20, so I expect to use blocks, covered with the type of hydraulic cement that is used for cisterns. I will go five or six blocks high. They build sewage lagoons at pig farms, this way, so it will be easy to find someone to build it. By the time a block is purchased, laid, parged and reinforced the cost becomes approximately 50 cents each. Then there's a cost of a concrete pad. I expect to spend about $400 on the tank and then a little more for piping.

Whenever the water has been used enough times that I decide it's too cloudy, it will be used for irrigation. It may also be used for laundry water that will also be sent directly to the plants. My landlady in Cebu uses grey water laced with Tide, Downey and other commercial cleaners to grow her bananas. We will only use soap that we make from vegetable oil and lye. It works pretty well as bar soap, shampoo and laundry soap. So I'm not at all worried about putting it directly on food crops.

Sometimes it's nice to have water that is warmer than what nature provides. I'm perfectly comfortable in 80-degree F water, but my fiance would prefer 95 to 102 F, like a bathtub. So I expect to create a big bread box style solar water heater adjacent to the pool. On sunny days it's pretty easy to get water to the 160 degree range, based on tests I did in January. This hot water would be dumped into the pool just prior to use. Mosquitoes and other undesirable life-forms generally are harmed by temperature shock. So this will be part of how the water is managed.

Does anyone have other ideas on how water in an open irrigation tank can be kept a little cleaner for swimming and bathing purposes? I hope to avoid running any sort of filter, but I suppose something based on sand, charcoal or rice hulls might be okay.

These photographs illustrate the simplicity of this type of tank. I won't be insulating or burying mine.

The plan seems valid if rain is adequate enuff to drain and replenish the water when needed.

I'm an advocate of a couple of minnows for mosquito larvae. They shouldnt need fed or aerated. The poop wouldnt be enough to be an issue. In my mind you are thinning the mosquitos. Eating the larvae will be better longterm over discouraging them. That just results in them laying somewhere else where they will hatch.

You may be able to extend the time of emptying by draining off a little from the bottom a day after bathing. Plants in the water may be helpfull.

That would be all good, if I planned to keep water in it most of the time. I intend to use it more like a bathtub, where I fill it and then completely drain it. The water could be used for irrigation but also for laundry and watering stock. I may create another much bigger tank or pond where I would definitely have mosquito fish. But this is somewhere that I would use soap and shampoo and where I would pour in hot water from a solar collector, that would surely kill any little fish. Then there's the huge diurnal range , since I would probably cover it with  some greenhouse plastic  in order to reach the magic number of 100 Fahrenheit . Just about everything I do would kill the fish.

I don't anticipate ever keeping water in it for a full week. During the rainy season, you can get thousands of gallons per night falling on a house roof. But there can be multi-day breaks in that rain. I would use it when rain water is available and not use it when it isn't.

I intend to use some sort of pump as an electrical dump for my solar panels. Pumping water to a tank like this from a shallow well, would ensure a fresh bath every night. There would probably be times when I manage it at only one foot deep, so that it can get hotter each day. Then if I want to have it four feet deep, for some hot tubbing, we would empty the solar collector into it to top up the temperature.

I was in a few places where the water table was only about 7 feet down. So it would be pretty simple to pump a foot or two into the tank in the morning, use it for just that day or for a couple days and then open the gate and let it percolate to the water table. The system will be highly dependent on how far down the water table is.

So, I probably just want to find ways to extend water life or lack thereof, for a few days at most.

It seems to me that covering it with some kind of black plastic cover when not in use would serve you quite well. It would reduce the mosquito loads, reduce sunlight and the things that grow in it, and warm up the water all at once.

I'm always torn as to whether I should use clear or dark plastic. Shower bags use black plastic, but when there's not direct contact between the plastic and the water, clear plastic does a better job of heating things up. I'm going to need to find out which condition is likely to produce more listeria. That's probably more important than mosquitoes, when considering how often it will be emptied. Sunlight helps algae and mosquitoes. But I think listeria does better in the dark.

Even a little bit of soap can really harm lots of microscopic life. But then it doesn't seem to harm others. The soap we make is dirt cheap and we use it every day. The only issue there is that I would expect people to take a shower before using it as a hot tub, so any soap used would be rinse off before entering.

I would have no problem with always having a little bucket of Moringa Seeds and neem tea brewing by the pool. People tell me that just a little bit of neem takes care of mosquitoes. But India has massive amounts of neem and I bet if I went there, I'd meet a few mosquitoes. So obviously there's a certain concentration required.

Hey Dale,
have you thought about using an ozone generator with an air pump and bubble-making stone (like the things used for fishtanks)?

I have a 500mg generator with pump and it uses around 6 watts.

I may do something like that with drinking water, if Moringa filtration proves inadequate. But I don't think I will treat bathing and irrigation water. That could change if I find that I need a power dump for my solar panels. I expect that pumping water to elevation will be my main battery.
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I just went looking and found some that are incredibly cheap. I don't know how much ozone they produce or how much I would need. I guess it would be important to pre-filter everything first, so I'm not trying to oxidize dead bugs and sticks.

Dale Hodgins wrote:
Does anyone have other ideas on how water in an open irrigation tank can be kept a little cleaner for swimming and bathing purposes? I hope to avoid running any sort of filter, but I suppose something based on sand, charcoal or rice hulls might be okay.

:brainstorm: A protein skimmer modelled on the type used for aquariums, free floating to accommodate fluctuating waterlevels. Problems= Who do we coerce into emptying the collection chamber on a daily basis?

I've been reading up on the treatment of water using the mash left after oil is pressed from Moringa seed. It's used as a water purifier and clarifier on a commercial basis in India. They even use it to clarify sewage sludge. The seed contains saponins which cause contaminants to clump and gather at the bottom of the tank.

Because of the saponins, the seed mash can't be fed to animals. It can be used as a hand cleaner and it makes a high nitrogen compost.

My investigation into this technology, is bound to be much more important for my life in the Philippines, than having a swimming pool. I expect that this will be my primary cleaner and disinfectant. I already make soap and already intend to make Moringa the primary plantation crop, so the whole water treatment thing is a huge bonus. There's also a plan to start a small laundromat for my mother-in-law to operate. She currently does laundry in a big plastic tub and is able to earn about $0.50 for her efforts. Water treated with moringa requires less laundry soap. Poor people use only the detergent quality of the plant when washing clothes by the river. There may need to be a separate cistern that contains enough water for her daily usage. The seed and oil has a pleasant odor. I wonder if any of that would carry through to the clothing after going through treated wash water.

This article doesn't give a lot of numbers. Several of the videos and articles out of India mention a better than 99% bacteria reduction. I will buy a microscope, so that I can see what is in my well water, before and after. I guess I should first find out if there's any microscope that can see stuff that small and not cost a million dollars.

https://treesforlife.org/our-work/our-initiatives/moringa/other-uses/water-purification/household-water-purification

Here's the important part ...

How to Purify Water with Moringa Seeds:

Allow the Moringa seed pods to dry naturally on the tree before harvesting them.

Remove the seed husks, leaving a whitish kernel.

Crush the seed kernels to a powder with a stone or mortar.

Mix the powder with a small quantity of clean water in a small cup.

Pour the mixture through a tea strainer or sieve into a cup. It's best to cover the strainer with a piece of clean cloth.

Add the resulting milky fluid to the water you wish to purify.

Stir quickly for 30 seconds, then slowly and regularly for five minutes.

Cover the water and do not disturb it for at least an hour.

The clean water may be siphoned or poured off the top of the container.

50-150 mg of ground Moringa seed treats one liter of water, depending on how clear the water is. We suggest experimenting with amount of seeds and stirring times to find what works for you.

The seed cake left over after extracting oil can still be used for water purification.

I live in a place where growing plants can only happen with the help of irrigation, and we've used a storage pond for the past 20+ years. We also swim in it. We're not tropical, though, so some factors are very different from your situation.

The schedules of filling it for swimming/bathing, using it for necessary irrigation, draining it fully to break the mosquito life cycle, and keeping it full for storage for a later need, may clash. It can be a little hard to juggle all of those. But certainly better than not having it at all!

Vertical walls like the samples you showed above could be dangerous for non-swimmers who decide to go in for a bath. And are there dogs there? If they jump in could they get out? Vertical walls are also structurally harder to build strong enough to hold the weight of the water. If you could build it partway buried, and partly bermed up, with sloping walls, it might be safer. But it would take more space, which might become an issue depending on the land you end up getting. And it would allow more evaporation which might be less of an issue in the humid Philippines than in my location in the high desert, but we still find that sloped wall shape more desirable.

I'm sure you're more expert on this kind of detail than I am, but for breaking the mosquito life cycle, make sure to have the floor sloping with the drain at the lowest point.

Last year we had cement plastered our irrigation pond so it became more pleasant to swim in than the previously clay-bottomed version. So all our students were swimming in it daily, maybe 20 - 40 people using it over the course of a warm day, and I think ringworm (a skin fungus) went around. We were draining it every two days for irrigation, but maybe not fully because we don't have a mosquito problem most of the time. This might not be an issue for you with very few people bathing in it. Ours is much bigger than yours, but it still happened.

That is awesome. A very inviting place when you're in a hot dry environment. I will definitely make a means of escape, but also I expect there to be a chain-link lid or some other barrier to keep children and dogs out when it's not in use.

I will try the neem and moringa, to see how well they perform. I expect that every draining will be a complete emptying, that will include scrubbing the sides occasionally. Moringa contains saponins which can be used as a foliar spray for aphids, the same as you would use Safer's soap.

Because I will be producing moringa oil for export, I expect to have vastly more seed cake than I would need for a pool your size. I'll start out with the recommended amount, but I will quadruple it if necessary. There's no real cost to it. One way to make sure that the water is always suitable for swimming, would be to use it as the treatment tank for laundry water, so that it would be treated each day. This reduces the amount of laundry soap needed, by settling out particulates and they say it works as a water softener. Any excess not consumed in settling out, may leave swimmers very clean.

Some potted neem, may be planted around the area and I could see spraying the surfaces with neem tea,

Mint.  Mint grows just about everywhere and there are many creepy crawlies that don't like it. So a bucket of that could brew in the sun,  waiting until swim time.

Non insect critters. I would like to keep snakes, rats and other larger creatures out out the water. I will see if there's anything botanical guaranteed to repel snakes. There are several nasty water snakes found in the Philippines, but I'm not going to be connected to a body of water. I would like to keep things like king cobras, spitting cobras and the Philippines Cobra from calling my pond home. I made the mistake of walking through a cornfield at noon. I met two cobras in 5 minutes. Luckily they didn't want to meet me, and they crawled into rock piles.

Water 3 ft deep can easily be contained in a concrete block vessel this size. There are many examples of sewage lagoons built in the same way.

Are you going to reinforce your walls with something?  Will it withstand to repeated drainings and fillings?

eco pools  

biosand filter works great too you can even drink the water. I have constructed and use couple of this. https://www.cawst.org/services/expertise/biosand-filter/more-information. This has a max capacity of 200 liters. If you need double that, double the cross section area. the height is same. Very easy and cheap to make if you improvise. I use big plastic bags and sacks. Cost around P150 philippine money plus my labor. I collected free beach sand. not the one near the water but somewhere up. The crucial part is choosing the right sand size but not difficult. I did it right the first time.

Dale Hodgins wrote:

These photographs illustrate the simplicity of this type of tank. I won't be insulating or burying mine.

Hi Dale,

Do you know how the tank in the photograph is covered and how it is cleaned out?

Thank you in advance,

Tiffane Dx

Tom Connolly wrote:Are you going to reinforce your walls with something?  Will it withstand to repeated drainings and fillings?

I will use steel rebar at more than the recommended rate. And I expect that along the top grade beam/ sitting area not shown in the pictures that I posted, I will put a double or triple run of rebar in that. There's no real stress in filling and emptying. Pressure is always at its highest when the thing is full. The rebar is mostly the hold it together if it's breached by an earthquake or some other calamity. Usually when something like that happens, you empty it and put a new layer of parging.

julian Gerona wrote:eco pools  

biosand filter works great too you can even drink the water. I have constructed and use couple of this. https://www.cawst.org/services/expertise/biosand-filter/more-information. This has a max capacity of 200 liters. If you need double that, double the cross section area. the height is same. Very easy and cheap to make if you improvise. I use big plastic bags and sacks. Cost around P150 philippine money plus my labor. I collected free beach sand. not the one near the water but somewhere up. The crucial part is choosing the right sand size but not difficult. I did it right the first time.

I probably won't need the filter for the swimming pool since I plan to use the water for irrigation pretty regularly, but I quite likely will need something similar for a pond near the house that may or may not be used for swimming.

Tiffaney Dex wrote:

Dale Hodgins wrote:

These photographs illustrate the simplicity of this type of tank. I won't be insulating or burying mine.

Hi Dale,

Do you know how the tank in the photograph is covered and how it is cleaned out?

Thank you in advance,

Tiffane Dx

I don't. My tanks will be completely above ground, since there's no danger of freezing. This allows for a simple 3 inch PVC pipe with a ball valve, to allow gravity draining. The drainage of each tank will be site specific.

I don't know what type of roof they are using on these cisterns. I think one of my photos may have been of a tank that was destined to be a sewage lagoon. When it's meant to be just for storing water, concrete roof might be appropriate. It could be given a roof, similar to any house or shed or I could be covered in glass or plastic. For my purposes, I might use one of those floating insulating pads like you see on swimming pools. But it might also need a more solid cover to keep children and pets out.

When covered and when the concrete is painted black, I would expect to get over 100° Fahrenheit each day. Then the water can be held into the evening until it cools down enough, or some cold could be added. The temperature makes it into the 80s almost every day of the year.

If a planned laundromat really takes off, I would add some flat plate solar collectors and use a tank like this as a hot water tank. Then, in the evening it could be topped up with enough cold water to make it comfortable for swimming.

I'm not a big fan of circulating pumps, or mechanical systems of any kind, for swimming pools. I just want a hot tub of water, not a bunch of maintenance. The one exception to this is that we might get a 12-volt bilge pump and use it to circulate water. We can put a screen bag on it so that it cleans up debris.

Here's a few of the most unusual conversions of a swimming pool, that could occur.

There's a good chance that we will use it for a while and then decide that we want something bigger and better or that we build a more natural pool as pictured above. Then there's the question of what to do with the existing vessel. I have a few ideas.

1. Water heater for a laundromat and possibly small scale processing of banana fibre. With nothing more than black paint, and a covering, water can get up to over 100 degrees on most days in the Philippines.

2. Methane digester. This would be a very simple conversion. EPDM Rubber top, then a feed tube and a little bit of other piping.

3. Irrigation tank. It wouldn't need any alteration for this. And it could also end up being a giant manure tea delivery system.

Any open tank that is used for irrigation water, will have azolla covering the entire surface of the water. There would still be transpiration losses, but we get something that's 25% protein out of the deal.

4. Aquaponics tank. I'm not convinced that electricity powered aquaponics makes sense, but I would give it a whirl if I had a spare tank sitting around on a farm.

5.Silo. That's right, let's pickle some animal feed. Probably not going to happen with the tank closest to the house, but there will be many areas of the farm where a tank may be constructed for one purpose and then it's no longer needed for that purpose. Any of these could become water storage, or a silo, since required alteration is minimal. I've seen a few silos that are roughly this shape, on YouTube. They are a simple batch system, and once the seal is cracked, the feed should be used up within 10 days. So something this big wouldn't be needed until there are 40 animals to feed.

... Well, I think that's about as far off topic as I've ever gone, when discussing a swimming pool... Hot water, manure tea water, methane , fish, or corn and azolla silage. All perfectly acceptable things to put in a swimming pool, if you don't need it anymore..... I think this little segment could have been called, what can I do with this unused concrete cistern? That's just how my head works, when I should be sleeping. ☺

Sounds like you've got a great plan for your above-ground pool and irrigation cistern! I love the idea of using Moringa and Neem to keep the water clean and clear.

If you have the space, I would definitely build a natural swimming pool, you can stock it with some tilapia as well and have a food source. You can definitely make a natural pool that also serves as irrigation, you just have to plan, how much water will be going in, approximately when it will be going in, and how much will be going out, and when it will be going out, to make sure you keep the level needed for the system of the pool to keep functioning.

Sounds like you've got a great plan for your above-ground pool and irrigation cistern! I love the idea of using Moringa and Neem to keep the water clean and clear. I also like the idea of using solar energy to heat the water. A suggestion for keeping the cistern and pool area clean would be to consider a residential pressure washing service like this https://sparklewash.com/residential-pressure-washing/ every once in a while. It's an easy way to keep the area looking great and ensure the longevity of your cistern and pool. Keep us updated on your progress!