Rainwater Collection?

[Simi 60]

Whats the side of the roof like?
Flat with roof close enough to 90 degrees?

[SKMT]

Originally Posted by Simi 60

Whats the side of the roof like?
Flat with roof close enough to 90 degrees?

Yeah.

[Simi 60]

Sikaflex or 5200 to the roof edge



https://www.bunnings.com.au/brutus-4...lding_p1100619

[Eigenvector]

Originally Posted by SKMT

Ok, so my next question is what kind of in-line filter will work just with the gravity pressure, while draining fast enough that i'm not backing up water over the rim in a down pour? This water is mostly for showering and sh*ting in. If i'm cooking with it, its for boiling something. So it doesnt have to be immaculately pure, just wanna keep my tanks (and fresh water pump) free of debris.

Given that you don't have a lot of head pressure for filtering and a couple other thoughts.


Sizing of your collection system. Figure out what you can live with. I have a remote building (with workers) that has been fully functional for 15 years on rainwater collection. I have 4 x 3500 gallon food grade tanks. The 60'x120' building will nominally generate 3000 gallons per 1-in of rain. These tanks are at the corners of the building and connected via 6-in pvc pipe. A good turd floater will overwelm these pipes but it's normally good enough. The decision was that larger than 6-in pipe and fittings was good enough. Figure out what's good for your area. Mine was based on published data for the area.


Roof Washer System. Per the attached sketch, the pipe system incorporates a overflow fill system. When rain starts, the first 10% (45 gallons as I recall) goes all the way to the end and has to back fill to the tee before water is collected. From the tee to the end cap is 45 gallons.
The cap has a 1/4 hole in it to auto reset. So, when it rains, the first 10% containing bird, bat, dust ect is diverted. If it quits raining for 15 min or so, the roof is still clean and the pipe hasn't drained yet.


Every once in a while I pull the cap off to see what's in side. Mostly red dust. Did find a bat once.



Since we drink the water, I run a 5 micro pre filter in front of a UV filter. I have pressure drop gauge to judge filter replacements and regularly test the water. It normally runs at around 5 psi across the filters. On the 3rd set of 24" filters after 15 years. I don't have leaves to worry about.


For your case I'd do a simple washer system as described with a mesh screen (or stainer) off the tee just in case.


Hope this helps

[Dymaxion]

Perhaps buy or fabricate a "day tank" that holds a gallon or so, connected to the roof gutters. Drop in a cheapo bilge pump and switch, then use its outflow to push through suitable filter(s). I'd add some chlorine periodically.

[Mr B]

I use this, Triangular peice of Tarpualin, This gives me pure clean drinking water,
No bird crap, dust or other impuritys in it,
It rolls up very small when dry and I keep it in a locker,
Takes a couple of minutes to fill a 25 litre drum, 5 gallon drum, With rain water,
Then straight into my freshwater tanks,

[thinwater]

I set up my PDQ for rainwater collection using existing gutters and a 1 micro filter I refer to as my "baja water filter." I can use it to filter rainwater, hose water, or even water I load from jerry cans.


It is cleanable, sanatizable, cheap, and dead simple. I basically used nothing but rainwater for a year of frequent but not full time cruising. The tank was always full when I came to the boat. On the average, I collected 8-10 gallons per day until full.



https://www.practical-sailor.com/bel...y-water-filter

[noelex 77]

Originally Posted by Dymaxion

Perhaps buy or fabricate a "day tank" that holds a gallon or so, connected to the roof gutters. Drop in a cheapo bilge pump and switch, then use its outflow to push through suitable filter(s). I'd add some chlorine periodically.

Our new boat has a built in system along these lines. Deck water is collected by simply plugging the two deck water drains with some lever action plugs. The rainwater passes through a coarse mesh filter to a 140 litre under deck tank. From here it is pumped via two 10 inch fine filters before entering the main tanks.

The system was set up as a backup to a watermaker, but it has been so successful that we are yet to install the watermaker. It has given us an abundance of fresh water, so much so that we collect water only a small fraction of the time. This is cruising a wet climate (Netherlands, Norway and the UK), but it collects so much water that it should be useful at least in its intended role as a backup to a watermaker in even much dryer conditions.

[Steven UK]

Originally Posted by Simi 60

Sikaflex or 5200 to the roof edge



https://www.bunnings.com.au/brutus-4...lding_p1100619

Like this idea for the solar panels...

[SKMT]

Originally Posted by thinwater

I set up my PDQ for rainwater collection using existing gutters and a 1 micro filter I refer to as my "baja water filter." I can use it to filter rainwater, hose water, or even water I load from jerry cans.


It is cleanable, sanatizable, cheap, and dead simple. I basically used nothing but rainwater for a year of frequent but not full time cruising. The tank was always full when I came to the boat. On the average, I collected 8-10 gallons per day until full.



https://www.practical-sailor.com/bel...y-water-filter

1 micron seems really fine for gravity pressure...does it back up in a downpour (causing collecting water to pool and overflow)?

[thinwater]

Originally Posted by SKMT

1 micron seems really fine for gravity pressure...does it back up in a downpour (causing collecting water to pool and overflow)?

Not as much as you would think. There is a lot of surface area.


It typically flows about 3 gpm under gravity, so I suppose it would during the peak of a real cloud burst. But it would really need to be coming down. On the other hand, during that sort of horizontal rain, I suspect much just sprays off.

The bags are available in 1, 3, 5, 20 and 20 microns, so chose your poison, but the water quality will be better and final filter life longer with finer bags.

My water system also included regular chlorination (very light) and final filtration/dechlorination through a carbon block filter The block filter lasted thousands of gallons.


---



I actually designed the system for a friend on a mooring, based on experiences with chemical processing. He just wanted water to wash the boat. But I like it and upgraded mine to supply drinking water. It was better than the marina well water, which was not that great.

[Mike OReilly]

Originally Posted by Mr B

I use this, Triangular peice of Tarpualin, This gives me pure clean drinking water,
No bird crap, dust or other impuritys in it,
It rolls up very small when dry and I keep it in a locker,
Takes a couple of minutes to fill a 25 litre drum, 5 gallon drum, With rain water,
Then straight into my freshwater tanks,

I like it Mr B. Avoids all the problems of having to clean the collecting area. How large is your tarp?

I came across this product, which seems like what you're doing B.

https://www.newpig.com/pig-roof-leak-diverter/p/TLS462

Seems to me it would be fairly easy to install some sort of valve with a spigot. Diverting it through Thin's filter would make it bomb-proof.

[Tellie]

Originally Posted by SKMT

I've been debating watermaker vs collection. With all my roof area, 1inch of rain will yield at least 100gallons. Based on avg monthly rainfall in Miami, my 300gal of tanks will be overflowing at least half the year. And even in the driest winter months, the avg rainfall is about 2inches, so i think its worth a try before a watermaker, because auto-collection would require almost zero attention once built.

Here's my number.

[dannc]

Regarding "automatic" rain water collection and letting the water flow clean...

Years ago I remember seeing a device that would collect the first part of the rain water, and after a period of time during which the collection surface would be clean, then divert the rain water to a cistern. This was for use by houses.

Instead of trying to describe what I dimly remember, I found this website from Texas that is loaded with information, http://www.arcsa-edu.org/Files/Texas...Harvesting.pdf. Page 8 talks about the "First flush diverters" and has design parameters. There is discussion about how much water should be diverted based on the area used for water collection.

I found the link on a website devoted to water harvesting. Lots more to read on that site if one wants too, https://www.arcsa.org/page/101

Later,
Dan

[hpeer]

Great thread.

We have a largish bimini with heavy zippers (for sun screens) around 3 edges. I’m going to talk to my sailmaker about making gutters that will zip to the bimini. If that is possible I’ll need to figure out the filtration and filling strategy.