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Is lime wash bad idea for rainwater catchment roofs?  RSS feed

 
Erik Rowberg
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I build brick masonry roofs and catch the water.  The roofs are surfaced with a clay/sand/lime plaster and then lime washed.   Is there any negative affects to the water other than it could become harder?    Seems that  most ground water percolates through limestone .

And if you are interested this lime-clay plaster works better than a sand cement plaster, which cracks and allows dampness.
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bob day
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Location: Central Virginia USA
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Just some idle thoughts about the issue

seems like it would be ok  but the real test would be to measure the ph of water in the tank.

Some people  even pay extra for alkaline water, and I believe some of that has calcium added.

I suppose different LW mixtures would have different amounts of lime washing off.

Rainwater tanks sometimes have a lime stone block added specifically to reduce the acidity of rain water, and or to precipitate out heavy metals.

My personal belief however is that highly mineralized water is bad for the body--not so that it would kill you right away but more in the sense of calcifications clogging kidneys, building bone spurs, etc.

So while you can get away with it for bathing and such,  I would use an  RO  filter for any rain water for drinking and cooking

plumbing  deposits might also become an issue at metal fittings and hot water tanks
 
Sebastian Köln
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Location: Germany · Schleswig-Holstein · Eutin
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bike toxin-ectomy
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We have very hard tap water here (lots of limestone in the ground). The plus side is that it does not dissolve copper pipes.
The downside is that it builds up everywhere. Heating it up accelerates this greatly, which is the reason, we don't have an electric boiler anymore.

The roof looks amazing! I have to try lime-clay myself.

If I had to neutralize this water, I would probably build a small pond/bog with clay and a lot of plants and have a slow input of the alkaline water into it.
The plants and bacteria should neutralize the lime (I hope).
 
Phil Stevens
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Location: Ashhurst New Zealand
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Hi Erik - I've been working with different lime plaster variants but haven't tried adding clay to the mix. What sort of proportions do you use, and have you added pozzolans of any sort? It looks fantastic in the photos. How often do you limewash it?
 
Erik Rowberg
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Sebastian Köln wrote:We have very hard tap water here (lots of limestone in the ground). The plus side is that it does not dissolve copper pipes.
The downside is that it builds up everywhere. Heating it up accelerates this greatly, which is the reason, we don't have an electric boiler anymore.
).



Thanks Sebastian this is helpful.

erik
 
Erik Rowberg
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Phil Stevens wrote:Hi Erik - I've been working with different lime plaster variants but haven't tried adding clay to the mix. What sort of proportions do you use, and have you added pozzolans of any sort? It looks fantastic in the photos. How often do you limewash it?


clay- sand- lime- wood ash   4-6-1-0.25

wood ash we just started using on the last roof.

i am adding limewash every year for now.
 
Garrett Connelly
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Would you be interested in explaining your process with a photo essay on ferrocement.com ? There's a contact button there.

Garrett, the web caretaker
 
Marisa Majemu
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Location: Denver, United States
greening the desert solar urban
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This is a VERY common practice on islands such as Bermuda. They use the lime on roofs to purify the rainwater since they are so dependent on what falls from the sky for their freshwater supply. You might want to check out  how some of those places put this in place. They are the experts!
 
Krofter Young
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Location: Baja Arizona
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Judging by the look of the vegetation around the home it appears that the soil there is somewhat acidic.  If you were to use the water to irrigate, the alkalinity that the rain water picks up from the roof will be largely neutralized in the soil.  If you live in an area with soil that's already alkaline, your soil could become so alkaline that crops may perform poorly.  If the water is used for drinking and bathing you might see a chalky development in your skin and hair that becomes more unruly.  Could lead to kidney stones as well, unless you take dietary steps to avoid these things.
 
Malcolm Thomas
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Very nice roof there , well done . Just curious about how you made it ie the structure did you use wood profiles and whats under the lime wash is it clay or cement .
I think lime wash on walls has a great look too and is mildly antiseptic and is porus so better than portland cement . Might want to get your water tested at a lab before you drink it , we use our roof water off clay tiles for chores etc but not to drink, birds on roof equals droppings etc !!!. Our water goes to a brick cement lined settling tank first and mostly we boil or heat the water through a gas boiler before use , Never for drinking .
 
Garrett Connelly
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About drinking rainwater with bird poop maybe on roof.

What should one do about breathing dust with dried bird poop in the air via walking feet or rolling car tires?
 
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