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Best Rainwater Catchment System for Potable Water?

 
pollinator
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We're trying to finalize our building plans and I need some help with the rainwater system.

My biggest question is... where is the best place to put my tanks? We're planning on starting with two or three 5,000 gallon plastic tanks.
I see that I can either put them directly next to our home for the water to fall directly into the tank, or have it a ways away and bury the pipe in the ground leading to the tanks. We have a pretty good slope to be able to do this and still have the water enter the tank- though I guess the pipe would stay full of water in this case unless the tanks are lower than the buried pipe? That seems kind of sketchy to me if I want the water to be potable.

Either way, getting all of my gutters to meet in one central location to dump the water into my tanks is proving to be beyond my scope. Or am I over complicating things?
Perhaps I just need to invest in a good rainwater catchment book?

I'm attaching pictures of my house plans for reference, if more pictures are needed let me know. Pardon the cruddy program I'm using, I think you get the gist!
If I have tanks near the home they'd go in the back on the gable side between the windows. If they are farther from the home they'd be down hill from the front of the house. House is mostly a 38x38 square.
Floorplan.png
[Thumbnail for Floorplan.png]
Roof.png
[Thumbnail for Roof.png]
Back-of-House.png
[Thumbnail for Back-of-House.png]
 
pollinator
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Have you spent much time on the property? From what I've seen, usually the side that is windward to the prevailing storms generates nearly twice as much water as the lee side. That's where the payoff is when capturing rainwater.

Perhaps I've misunderstood, but I have concerns that you might believe rainwater is potable. Each raindrop starts with a dust particle that originates somewhere, and carries microorganisms from that soil along with it. Roofs and drains collect bird and bat poo, and legionella loves warm, stagnant tanks. Unless you have very regular flow volumes to flush the system, it's my opinion that captured rainwater should be considered raw water and treated before it is ingested. (Pardon me if this rant is off base.)
 
pollinator
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Location: Bendigo , Australia
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Douglas, technically you are both right and wrong.
Firstly, Detritus can be dealt with by the use of a first flush unit, which ensures dust and bird poo etc does not enter the tank.
Secondly, by having large volume tanks, the water can clean itself over time.
The use of 100 litre tanks as storage can be dangerous.

I have captured and used rainwater in 20,000L tanks for 40 years, as have most rural properties in Australia, illness as a result is not an issue.

One benefit of having the tank down the slope is that while you will continue to have a 'wet' pipe system, IE full of water, you can install a drain cap near
the tank to dump the captured water when you feel like.  Maybe once a year.
If you want a 'dry' system have the tank further down the slope so all water drains to the tank.
I would think about first flush units on each down pipe, if you expect lots of dust etc.
Pipes around the house will usually be easier to manage, but think about a drain cal near each down pipe just in case you need to unblock a down pipe.

Can you lift the carport roof so its gutters are higher? Which would help if your tank is going to be near the house.
 
Rebecca Blake
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Douglas,
Good point about the wind. I’ll need to head out there during a storm/cloudy windy day some time. I did go when it was quite windy the other day and based on those observations the side with the carport will receive a good chunk of rain.

I have spent a good chunk more time on the neighbor’s property (they’re my friends so I’ve been going there since before we even thought of buying property here). I’m using my wind analysis of their property a tad bit but understand since this is the hill country it could very well vary on our specific acreage. Hills change things.

Thus far the biggest thing I have noticed is the wind tunnel our driveway creates, but I’m not sure that’s the case for the higher winds directing the rain.

Not sure it matters too much if we’re looking to gutter the whole thing (minus the small part of roof over the front door).

John,
Thanks again for your help. Are there any advantages to having a wet versus dry pipe? With our slope I bet we could do one of any 3 systems, dry pipe right up against the house, wet farther down hill, or even dry pipe down hill.
I’ll have to take my husband out and shoot some grade to double check.

If I go with a dry pipe, would away from the house be better? Or is this site specific so you can’t say?
 
Douglas Alpenstock
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John C, good comments. A good method for managing potential hazards makes a big difference.

I'm curious about regional variations. I wonder if the rainwater collected during your long wet season would be generally cleaner than the short-lived, aggressive thunderstorms I get in my area. I can literally see the sediment dropped with the rain collected in a clean pail, and a car left out will be quite dirty when the water evaporates.

I suppose Texas in hurricane season gets long bouts of rain that is perhaps cleaner than I imagine.
 
John C Daley
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A few answers here;
How long can you store rainwater for drinking?
Rainwater can be stored from anywhere between one week and indefinitely.
The more consideration you put into your storage system – using the right materials, preventing algae and mosquitos – the longer your rainwater's shelf-life.

Here is a view of Wet vs Dry. I dont agree with all of the comments, but we always have differing views anyway.
wet vs dry

Now the mozzie situation suggested with a wet system can be sorted by having a first flush system at each down pipe, because they have a filter for big stuff, a mesh for smaller stuff that also stops mozzies.
The system itself catches dust etc within itself.

Douglas, our rainfall is spasmodic with only 14 inches a year at the moment.
We do get the big dust  and rain events that trash clean cars etc and makes everything look red in our case.
A first flush system would deal with it.

Another tip, is to have a floating pipe attached to the outlet point within the tank.
Then have the entry to that pipe floating say 6 inches below the water surface, heres why cleaner water
 
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Location: Central Indiana, zone 6a, clay loam
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My less than perfect plumbing instincts tell me you dont want water sitting in a pipe... but might be less complication prone than siting the tank downhill. Im not really sure on that one.

As far as books go, I would highly recommend Art Ludwig's book simply called "Water Storage." I also think any of John C Daley's past posts on this forum are a great resource. The most important idea aside from first flush is that with a tank as large as you are talking about, you just avoid pulling from the bottom where sludge settles, or the top where other things float to, and the water will be cleaner than anything most municipalities could produce using flocculation and chlorine. A few inches below the surface using a floating movable intake is perfect but a low intake above sludge level is simpler and works almost as well. If you have any doubts you could look into slow sand filters but I don't think this is necessary with those large of tanks when properly plumbed and maintained. (We use a slow sand filter but operate from 275 gallon ibc totes with less than ideal plumbing) Good luck!
 
Rebecca Blake
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Dietrick Klooster wrote:My less than perfect plumbing instincts tell me you dont want water sitting in a pipe... but might be less complication prone than siting the tank downhill. Im not really sure on that one.



Negatory. It’s definitely not less complication prone because the tanks would need to be downhill in order to have the wet pipe! It’s combining two complications, in fact.
 
Douglas Alpenstock
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Here are some credible links I came across regarding water quality, design and maintenance. Very interesting! They align quite well with what John C has been saying.

https://www1.health.gov.au/internet/main/publishing.nsf/Content/0D71DB86E9DA7CF1CA257BF0001CBF2F/$File/enhealth-raintank.pdf

https://www.health.nsw.gov.au/environment/water/Pages/rainwater.aspx

https://www.water.wa.gov.au/__data/assets/pdf_file/0016/1762/99298.pdf
 
John C Daley
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Rebecca, I left out an important point.
If you have high winds etc, a dry system may be damaged more readily.
 
Rebecca Blake
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John C Daley wrote:Rebecca, I left out an important point.
If you have high winds etc, a dry system may be damaged more readily.



High winds as in tornadoes and hurricanes? We can get some violent thunder storms here and there but it isn’t really that alarming to me.
 
John C Daley
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Winds that may blow the dry system pipes away.

LOOK< LOOK!!! at this
water from Fog
Its something I have followed for a while, but now more information is easier to get.

I will start another topic on the same matter
 
Rebecca Blake
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John C Daley wrote:Winds that may blow the dry system pipes away.

LOOK< LOOK!!! at this
water from Fog
Its something I have followed for a while, but now more information is easier to get.

I will start another topic on the same matter



Ooh! I’m a big fan.
 
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On many Croatian islands rainwater is the only source of freshwater and it is collected & used for drinking, among other stuff, for many generations. I live on one of them so here's a few thoughts

Safety for drinking - beside already mentioned flush system, additional filter can clean rainwater that does fall into tanks. They have to be cleaned, how often depends on the desing, volume of filter and rain, and how much dust or sand etc. is in the rain. But also there is less detritus on the bottom of the tank. We have large concrete tanks with built in chamber for the filter materials, but I'm sure there are desings for filter for smaller tanks.
And flush system is a must for diverting rainwater out of the tanks when they are full, or some other system, but with flush you have a two-in-one thingy in terms of function ;-).

About connecting gutters & location of tanks - if you don't need to decide imediately a long-term solution for xy reason(s), other option is to start simple and observe for a year or two rain patterns and amount through months, water usage, and how fast/slow your tanks fill and empty. With that information you can then decide what is most appropriate for your situation.
For example - do you need to connect all the roof surfaces to fill all the tanks through the year? Maybe connecting just two biggest surfaces would be enough? Or some other combination? Also maybe put the tanks near the house first and see if it works like that...


 
Rebecca Blake
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Mare Silba wrote:On many Croatian islands rainwater is the only source of freshwater and it is collected & used for drinking, among other stuff, for many generations. I live on one of them so here's a few thoughts

Safety for drinking - beside already mentioned flush system, additional filter can clean rainwater that does fall into tanks. They have to be cleaned, how often depends on the desing, volume of filter and rain, and how much dust or sand etc. is in the rain. But also there is less detritus on the bottom of the tank. We have large concrete tanks with built in chamber for the filter materials, but I'm sure there are desings for filter for smaller tanks.
And flush system is a must for diverting rainwater out of the tanks when they are full, or some other system, but with flush you have a two-in-one thingy in terms of function ;-).

About connecting gutters & location of tanks - if you don't need to decide imediately a long-term solution for xy reason(s), other option is to start simple and observe for a year or two rain patterns and amount through months, water usage, and how fast/slow your tanks fill and empty. With that information you can then decide what is most appropriate for your situation.
For example - do you need to connect all the roof surfaces to fill all the tanks through the year? Maybe connecting just two biggest surfaces would be enough? Or some other combination? Also maybe put the tanks near the house first and see if it works like that...




Thank you for the recommendations!

According to my calculations we’ll need to use the whole roof if we want to be on 100% rainwater usage.
We’re planning on connecting them as soon as the roof is up, so we’ll be able to observe a little bit before we move in and need to use it but once we move we’ll be using it right away!
 
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