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Rain catchment system for whole home

 
Posts: 75
Location: St Charles, MO
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I'm trying to finalize all my build plans so I can move forward with putting a home on my land.  I have posted on here before about a rain catchment system and I am wondering if someone can weigh in a bit on my setup.  From my calculations with a 1400 sq/ft roof and Missouri's annual rainfall I will capture 35,000 gallons a year.  I had been recommended to use a 5000 gallon tank and am leaning towards this tank.  Shipping is a bit costly at $1400.  https://www.ntotank.com/5000gallon-norwesco-black-vertical-water-tank-x1750809  Beyond that I know I need a first flush diverter and a leaf guard as well as other piping and plumbing.  My biggest question right now is what type or size of pump should I use.  I am not 100% sure of what my water needs will be but currently it's just my son and I who will be living there.  It will be a 3 bedroom 2 bath if that helps.  I found a 1hp pump that had a decent GPM on this one but I don't know if these specs are enough for a 2-4 person household.  I'd assume I'd want to be able to create 40-60psi of water pressure.  https://www.ntotank.com/walrus-1-hp-electronic-control-pump-x5857184  As far as home filters, what is the consensus here?  I know there are claims rainwater has higher mercury levels, but other than that what types of elements am I looking to filter out of it?  Is a cheap filter useful and good enough or do people use higher end reverse osmosis?  I know some people use nothing, so I'm just looking for a consensus.  Thanks in advance!
 
pollinator
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I don't know to much about rainwater collection, but I do know that a black tank will get hot in the summer. So, you may want to have it sheltered from the sun. In my experience hot plastic makes the water taste funny, which likely means it's leaching in to the water
 
pollinator
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You will need the black tank to keep to sunlight from getting through and algae from growing.  You can paint over it with a lighter color to reflect the sunlight and keep it cooler if necessary.  Perhaps a shade that would let winter sun in to keep it from freezing in the winter.
 
Tim Siemens
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Good point about the alge. Never thought of that.
 
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Mike Bettis wrote: My biggest question right now is what type or size of pump should I use.  I am not 100% sure of what my water needs will be but currently it's just my son and I who will be living there.  It will be a 3 bedroom 2 bath if that helps.  I found a 1hp pump that had a decent GPM on this one but I don't know if these specs are enough for a 2-4 person household.  I'd assume I'd want to be able to create 40-60psi of water pressure.  https://www.ntotank.com/walrus-1-hp-electronic-control-pump-x5857184  As far as home filters, what is the consensus here?  I know there are claims rainwater has higher mercury levels, but other than that what types of elements am I looking to filter out of it?  Is a cheap filter useful and good enough or do people use higher end reverse osmosis?  I know some people use nothing, so I'm just looking for a consensus.  Thanks in advance!



Hey Mike,

Sounds like a fun project. That pump seems a little pricey and I think 1 HP is overkill for an above ground rain catchment system. I think I would get a $100-200 1/2 HP pump like this one on Amazon and buy a second one for backup. 10 GPM should be plenty. Just make sure you have a decent sized pressure tank.

For reference we're a two person household with 2 1/2 baths and two kitchens between our cabin and guest cottage being supplied by a SeaFlo 3.3 GPM pump and haven't had any issues. Note, we don't have a dishwasher or washing machine and use compost toilets.

For filtration we use two household filters and Berkey in the kitchen for drinking water. After a significant rainfall we'll treat our tanks chlorine. We have two 1500 gallon tanks so I'll typically treat the one we're not using and then a week later switch and treat the other one.

To keep the captured water cooler and protect the sun I'd recommend build some sort of a shade structure. See video and pictures of my set up below.



 
Mike Bettis
Posts: 75
Location: St Charles, MO
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Thank you Aaron. I will have some of those amenities like dishwasher and toilets so I may want a bit more gpm than 3 but I appreciate the input. That helps for sure. Do you have any idea what type of water pressure your pump runs and how it compares to city water pressure?

Yes tanks need to be black or at least no light transmission. My tank may end up sandwiched between the north west corner and a cedar tree, so I may not need to build any coverage but I had already planned to make sure it stays shaded regardless of how it ends up.
 
Aaron Yarbrough
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Mike Bettis wrote:Thank you Aaron. I will have some of those amenities like dishwasher and toilets so I may want a bit more gpm than 3 but I appreciate the input. That helps for sure. Do you have any idea what type of water pressure your pump runs and how it compares to city water pressure?



Our pump is 30-50 PSI. Most municipal water supplies are in the 40-60 range.
 
pollinator
Posts: 3742
Location: Massachusetts, Zone:6/7 AHS:4 GDD:3000 Rainfall:48in even Soil:SandyLoam pH6 Flat
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Average American Water Usage
Toilet = 16gal
Shower/Bath = 16gal
Faucet = 14gal
Clothes washer = 11gal (77gallon/week)
Leak = 9gal
Misc = 3gal
Dishwasher = 1gal
Total = 70gallon per person per day

Daily Water Usage = 70gal/person * 2person = 140gallons
Monthly Water Usuage = Daily Usage * 30 = 140gal/day * 30day = 4,200gallons

Wet Season = April to August with averages closer to 5inches/month
Monthly Water Production = Roof Size * Rainfall * 0.635 = 1400sqft * 5inch * 0.635 = 7000 * 0.635 = 4,445gallon/month
Your production is more than the average american usage so you are golden

Dry Season = September to March with average of only 3inch/month (just 2.7inch for Feb)
Monthly Water Production = Roof Size * Rainfall * 0.635 = 1400sqft * 3inch * 0.635 = 4200 * 0.635 = 2667gallon/month
You will have to reduce your daily water usage by 36%  when compared to the average american during the drier season or better yet just base your entire yearly usage on this drier average of 45gallon/person/day. If possible start tracking your daily usage now and then reduce it to 45gallon/person/day so that it is easier on you once you have the new setup/move


But back to you actual question. You will need a setup like below

Pre-Filtration
Leaf filter, 1st flush, overflow surface cleaner, floating outlet pipe, pump, pressure tank.
https://www.rainharvest.com/rainflo-agb-above-ground-rainwater-collection-bundle-4-inch.asp

Pump/Tank/PSI/FlowRate
FlowRate = shower*2 + basin*2 + tiolet*2 + kitchen sink + dishwasher + washer +  misc = 10gpm (avg of 1pgm per fixture)
(given that there is only 2ppl you can probably get away with just 4gpm, how many fixture will each person use concurrently? 2 at most)
PSI = 40 to 80
Presure tank= 30gallon+ ($300)
1HP Shallow Well Pump or Transfer Pump = 10gpm at 50PSI ($400)
They do have all in one pump (plus controller+pressure tank units) that cost $700 to $1000 e.g Grundflu scala2, the one you listed and the one in my package above.

Post Filtration
What are your views on ozone for microbes/cyst/virus/biofilm/etc control, how about just regular sediment filtration with "plastic/metal" filters?
https://www.rainharvest.com/jed-ozone-treatment-model-203-115v-a-c.asp
https://www.supplyhouse.com/iSpring-WGB32B-3-Stage-Whole-House-Water-Filter-System-w-20-Sediment-and-Carbon-Block-Filter

Backup/Buffer
with a 5,000gal tank and monthly usage of about 2,500, you will have a 2month buffer, thats really good and the long retention time of the water will mean that you will not get sick from a particular bacteria/ordor overwhelming the system from due to sharp changes/spikes. Is there a way for you the fill this tank from a well/stream/water-truck/neighbor in case of am emergency? What happens when a pump/etc is busted will you have a replacement on hand?

Frozen Pipe
In Florida I wouldn't worry about any pipes freezing but in MO or MA it's going to happen, whats your plan for when it happens?


 
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Posts: 5157
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S Benji, that image is a great representation of a system.
Aaron, That roof structure attached to the tank is clever.
 
S Bengi
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I am going to have to really encourage getting a underground tank, because you live in a cold climate. And you can only survive so long without a water source. The below tank cost the same amount as the one you shared in your original post.
https://www.ntotank.com/2500gallon-acerotomold-white-underground-water-tank-x9412811


You could also build a house around the above ground tank and insulate it, and maybe add a rocket stove, to warm it up to 40F
 
Mike Bettis
Posts: 75
Location: St Charles, MO
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Thank you so much for your information s bengi! It's all super helpful.

As far as your questions to me go. I like the idea of a backup pump. I may have one on hand. I do have a creek that will be within 50 feet of the house and likely cistern so I can use that if needed, in dry times it doesn't flow a lot but it's never dried up.

As far as freeze issues. These are my thoughts, feel free to weigh in anyone. What is wrong with one of those RV hose wrap heaters to use on the input side of the piping? It just plugs into an outlet and it wraps around your pipes or hose. Besides that I will have a 30" insulated crawlspace that I will likely place all the components in as far as pumps, etc. I could always build an external pumphouse like Aaron if the crawlspace doesn't pan out for some reason. Any above ground pipes will be insulated or heated with the RV hose wrap. As far as the above ground tank. Won't the mass of the water be enough to keep from freezing, granted I adjust my water usage in the colder months, or year round? I had wondered why the water is drawn from a float in some designs like yours, wouldn't the top and sides freeze before middle and bottom?

I'm happy for any input here. Less wasted energy and efforts will be essential.

Aaron thank you for all of your inputs as well as the YouTube video. It's very helpful. Maybe you can weigh in on the tank freeze since you get cold enough to freeze pipes.
 
S Bengi
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The reason why water is pulled from the middle vs the bottom of the tank is because the middle is the last place to freeze (think of a ice-cube), the bottom of the tank also has alot of sediments (organic and metal/etc) that we don't to pull inside the house. In fact I recommend pulling the overflow water from this 6inch of sediment layer. And the top layer usually has the least amount of particulates.  

The average low in Austin, TX in January is 40F but its 20F in Charles, MO. I wouldn't really call it the same cold climate. Also MO only get about 15F higher between day and night, but TX can be 30F hotter during the day so a 70F-80F high in the winter is normal for Austin TX.

If we go by averages the average temp for your town is below freezing for the month of January. With stretches of days with temp below -3F
It's also the dry season so your tank could be 3/4 empty vs full and overflowing in any random year.

I am happy to hear that you have a backup water source. I think it's worth it to try an outside above ground tank, and provide us with data about how much it freezes. It should be safe from freezing over for at least 300days out of the year.  

I think that blocking the wind will be a huge help, putting the tank inside of a winter greenhouse would do the trick.





 
Aaron Yarbrough
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Mike Bettis wrote:
As far as freeze issues. These are my thoughts, feel free to weigh in anyone. What is wrong with one of those RV hose wrap heaters to use on the input side of the piping? It just plugs into an outlet and it wraps around your pipes or hose. Besides that I will have a 30" insulated crawlspace that I will likely place all the components in as far as pumps, etc. I could always build an external pumphouse like Aaron if the crawlspace doesn't pan out for some reason. Any above ground pipes will be insulated or heated with the RV hose wrap. As far as the above ground tank. Won't the mass of the water be enough to keep from freezing, granted I adjust my water usage in the colder months, or year round? I had wondered why the water is drawn from a float in some designs like yours, wouldn't the top and sides freeze before middle and bottom?

Aaron thank you for all of your inputs as well as the YouTube video. It's very helpful. Maybe you can weigh in on the tank freeze since you get cold enough to freeze pipes.



As S Bengi intimated we don't typically get sustained freezes. A few years ago when Texas had a big winter storm and temps didn't get above freezing for a week we had about inch of ice at the top of our tanks. Exposed pipe is wrapped with Christmas lights and covered with insulation that's effective enough to keep water flowing during our relatively short cold snaps.

S Bengi wrote:I think that blocking the wind will be a huge help, putting the tank inside of a winter greenhouse would do the trick.



I really like this idea. You could even put your pump and pressure tank in it. I would still use a solid roof but put polycarbonate panels on the sunward side.

Another option I've thought about since installing my system is partially burying an above ground tank so the outlet plumbing is completely below frost line. For me 12 inches would do it. For you it would be 12-24 inches. Our water supply is rarely low enough that there wouldn't be enough water in the tank to resist external ground pressure. That's just my theory though.    


 
Mike Bettis
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I'm a huge fan of that idea Aaron. When I was designing a home with my architect I had actually planned to set the tanks into the ground a ways mostly due to the roof height but also as a way to insulate the tank. Underground tanks aren't a bad option but have two setbacks in my opinion, accessibility in case I need to get into the tank, and costs. As you can see the one S bengi mentioned costs the same and is half the size. So that's not a great option. I like the idea of setting it down possibly 30". My foundation will be dug to that depth anyway so I am sure I can build a gravel pit to place the tank in at 30" deep. I'll look into this more. I think the more earth contact the less likely it will freeze, especially at the bottom.
 
Aaron Yarbrough
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Mike Bettis wrote:I'm a huge fan of that idea Aaron. When I was designing a home with my architect I had actually planned to set the tanks into the ground a ways mostly due to the roof height but also as a way to insulate the tank. Underground tanks aren't a bad option but have two setbacks in my opinion, accessibility in case I need to get into the tank, and costs. As you can see the one S bengi mentioned costs the same and is half the size. So that's not a great option. I like the idea of setting it down possibly 30". My foundation will be dug to that depth anyway so I am sure I can build a gravel pit to place the tank in at 30" deep. I'll look into this more. I think the more earth contact the less likely it will freeze, especially at the bottom.



If you do a partial burial document it and take lots of pictures. Maybe even create a separate post here on Permies with a title like "Partially buried above ground water tanks" so its searchable. When I was designing my system I couldn't find anything on line. Options were either completely above ground or completely underground at twice the price or half the the capacity. Having worked with above ground tanks now I think they can definitely handle a hybrid approach.
 
John C Daley
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Have you considered installing a large tank in a basement, or a walled in barn with a heater.
Biggest problem I understand is the pipework and preventing it from freezing generally.
 
Mike Bettis
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Hello Aaron and John.  I didn't realize you had replied.  Aaron I was literally just coming back on here to figure out if there was any documentation on a partial burial.  It seems to be possibly the most cost effective way to place a cistern.  In my opinion the two issues are how deep and at what depth do I need to retain the pressure of earth.  At depth will I have any drainage issues around the groundwater around the exterior of the tank?  My thought is to bury it as deep as possible while retaining the earth with some type of possible gabion cage or concrete wall or tie system.  I'm likely going with a tank that is 152" tall, so if possible I'd like to bury it 60-96".  Using a gravel base to allow good drainage and then seal it up with dirt to keep earth contact and less water entrance to gravel base.  Concrete will be less economical and may tip the scale more towards an underground or legged tank.  But I think overall the poly vertical water storage tanks average around $1 per gallon while vertical or underground tanks average about double that.

John I'm glad you weighed in!  Well I guess installing a tank in my crawl space is an option and when you suggested that I researched some vertical and legged tanks but again they aren't very economical.  At least $2 per gallon.  At 5000 gallons I'd like to be closer to the $1/gal range since my water budget is $10,000 all included even gutters.  I think the crawl space could be an excellent place for the cistern so I will see what types of deals I can find on those style tanks.  I will have at least one more tank with a good vertical height above my home up the hill.  I am thinking about 2100 gallon for that one and it will be water supply for shop and upper end of property along with water for any mono crops I end up doing in the upper pasture like corn/wheat/oats.  All that being said, I will have a backup water source to possibly use with no pump necessary to get it down to my tank.  In addition, if my dreams come true I will have a barn uphill as well that will likely have the largest roof area and will hold at least 3000 gallons for gardens.  But there's no guarantees I get that far.

Please keep weighing in.  I'm only about 5 months from needing this project to be ready to install.
 
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Have a look at bladder storage for your crawl space. Much easier to install than a tank. As long as they're protected from direct sunlight and prolonged freezing temps, they last a long time.
 
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