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 10 CAL (QUICK LIME) IN CISTERNAs (Read 16074 times)
Bigyin
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Re: CAL (QUICK LIME) IN CISTERNAs
Reply #15 - Aug 16th, 2012 at 12:17am
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I'm fascinated to find out how many people on here rely on rainwater only for their supplies.  I'm one of the lucky ones who has a well and haven't had to worry about having enough water.  I don't know if you're living here yet Coldalba or just planning ahead ?
The rainfall here is erratic to say the least.  It's not unusual to have not a drop from say April to September and then when it does come it's an almighty torrent.  The average annual rainfall is about 600mm which equates to 600 litres/sqm of catchment area.  Now I estimate that I use about 500 litres a day for everything except drinking.  I realise that may sound extravagant to some people (but we don't have a shortage).  That comes out at about 182,000 litres a year or 182 cubo's and would require over 300sqm of catchment.   That's a lot of storage space and catchment area.  Then when you've collected all of that you've got to try and keep it sweet.  If I'm talking rubbish, please let me know.  Shocked

  

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John
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Re: CAL (QUICK LIME) IN CISTERNAs
Reply #16 - Aug 16th, 2012 at 1:01pm
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Bigyin wrote on Aug 16th, 2012 at 12:17am:
I'm fascinated to find out how many people on here rely on rainwater only for their supplies. I'm one of the lucky ones who has a well and haven't had to worry about having enough water. I don't know if you're living here yet Coldalba or just planning ahead ?
The rainfall here is erratic to say the least. It's not unusual to have not a drop from say April to September and then when it does come it's an almighty torrent. The average annual rainfall is about 600mm which equates to 600 litres/sqm of catchment area. Now I estimate that I use about 500 litres a day for everything except drinking. I realise that may sound extravagant to some people (but we don't have a shortage). That comes out at about 182,000 litres a year or 182 cubo's and would require over 300sqm of catchment. That's a lot of storage space and catchment area. Then when you've collected all of that you've got to try and keep it sweet. If I'm talking rubbish, please let me know. Shocked



This is exactly the problem with holding water in cisternas. It is not easy to keep sweet and clean. Even in small cisternas the water will go green from algae and once it's in, you can not completely eliminate it.

It is far easier therefore to have a large holding tank and feed the water in it through a cleaning system into a much smaller holding tank which is easier to keep clean because it can be used before it has a chance to go green again.

There are ways to keep even large amounts of water clean but it is not easy and it is not cheap. Chlorination is one way but it evaporates and has to be continually replaced. Lime is fine in wells but causes problems in cisternas (concentration levels, having to settle out etc.) The best way is to only clean your immediate needs completely and let the rest just filter through a slow sand filter to keep it fairly clean. please note the term 'SLOW' sand filter as opposed to any old sand filter.

If you want to see how effective sand is at cleaning water, try this:

Take a plastic 2 litre bottle. Put a small hole (1-2 mm diameter) in the lid. Cut the bottom of the bottle off. Turn the bottle upside down so the open end is at the top. Place some (a few) small clean pebbles in the bottle. cover the pebbles with small pea gravel to a depth of about 1 inch. Cover with washed fine sharp sand (washed river sand not building sand). Take a bucket and place a shovelfull of earth in it. top it up with water and mix thoroughly. Let it stand so the big lumps settle out a bit. Slowly pour the dirty water onto the top layer of sand and let the bottle fill slowly. catch the CLEAN water coming out of the hole in the bottle lid. Amazed? I was when I first saw it. Now scale it up and you have a sand filter.

NOTE:
This is NOT a 'slow' sand filter and is still very crude at this stage. The water may look clean but it is still full of germs, chemicals, and fine sand at this stage. Do NOT drink it.  Sad

John
  
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Bigyin
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Re: CAL (QUICK LIME) IN CISTERNAs
Reply #17 - Aug 16th, 2012 at 2:57pm
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That's all very interesting stuff John.  I obviously don't need it but I can attest to the problems caused by algae.  I pump up from my well into two cubo's in the garage connected in parallel.  The output is pumped to the taps/showers in the house.  The pipes from the pump to the taps run for about five meters along the inside of the garage wall and are the clear plastic type.  After a while, blue/green algae (I think) built up in the pipes to the extent of completely blocking one of the taps.  Happily I was able to dislodge it by moving the flexi connector about.  I flushed the system through with bleach which seems to have removed most of it and will lag the pipes later to keep the light out.
You mention sharp sand.  Do you know what the local builders merchants call it please ?
  

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Bigyin
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Re: CAL (QUICK LIME) IN CISTERNAs
Reply #18 - Aug 16th, 2012 at 3:01pm
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Re my last post but one.  I've just been chatting with a builder friend who gets around a bit and he tells me quite a lot of people rely on rainwater for their supply (who knew ?)  Undecided but he agrees with me that large catchment and storage are needed and most folk have to have delivered backup.
  

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PlanesPete
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Re: CAL (QUICK LIME) IN CISTERNAs
Reply #19 - Aug 16th, 2012 at 5:29pm
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Like many, we rely on a large cisterna (35,000L) which is filled by rainwater and maybe one 15000L delivery by lorry per year for 90. The pool uses most of it. Keeping the water good is easy, just keep the light and bugs out. We use a simple 1 micron cartridge filter before using the water in the house for washing. We used a reverse osmosis filter for drinking until reading a WHO report that warned against long term use due to mineral depletion. Might try a UV filter instead but it's bottled water for drinking at present.
  
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