Storing rain water


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I have a q about water (sorry if a little off topic)

If I fill my waterbutts with tap water.. And let it sit for a while will it lose the minerals Ect and be ok for drosera ?

If so how long would I need to let it sit b4 thinking of using it ?

Matt

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Hi Matt,

I suspect that this may have come from the strong chlorine smell that you sometimes get from tap water.

When asked how to get rid of that the answer is to put the water aside until it diminishes. As the others have said, minerals such as dissolved calcium carbonate won't reduce.

Cheers,

Steve

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Some people have treated tap water with acid, which can then cause salts to precipitate.

I am one of the some. I did this in the 1980's when I'd run out of rainwater in the summer.

I just checked, I still have the acid stored. and it was Sulphuric acid I used. I should add that my water is already on the acid side with a pH of 5.5 - 6.5. Of course he water butts have to be cleaned out afterwards to remove any precipitate.

Please don't ask me how much I added or where I obtained the information it was a long time ago. So long ago it was way back in the time we had books, I jest not, there once existed these things made of multiple sheets of paper bound together, with writing in them.

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Hi Fred,

I'm not sure I understand the chemistry being suggested here. I would have thought that the predominant problem in my area (hard water) would be calcium carbonate.

I think (could be wrong!) that the reaction would be:

Calcium carbonate + sulphuric acid -> calcium sulphate + carbon dioxide + water

The CO2 would mostly be list as gas (some might dissolve and acidity the water very slightly) and that leaves calcium sulphate which as far as I can tell has a greater solubility than the carbonate, so it less likely to precipitate out.

Of course once the acid had completed the reaction with all the carbonate the pH would start to fall as more was added which the plants might like but I am not convinced that it would reduce the level of dissolved minerals, just change it.

Did I get the chemistry wrong there?

Cheers,

Steve

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Steve, it was 30 years ago. I occasionally struggle to work out why I came upstairs with a teapot in my hand.

 

Suffice it to say that the plants did fine.

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Hi Fred,

I'm not sure I understand the chemistry being suggested here. I would have thought that the predominant problem in my area (hard water) would be calcium carbonate.

I think (could be wrong!) that the reaction would be:

Calcium carbonate + sulphuric acid -> calcium sulphate + carbon dioxide + water

The CO2 would mostly be list as gas (some might dissolve and acidity the water very slightly) and that leaves calcium sulphate which as far as I can tell has a greater solubility than the carbonate, so it less likely to precipitate out.

Of course once the acid had completed the reaction with all the carbonate the pH would start to fall as more was added which the plants might like but I am not convinced that it would reduce the level of dissolved minerals, just change it.

Did I get the chemistry wrong there?

Cheers,

Steve

Your chemistry is spot on, however calcium carbonate isnt the problem as it is insoluble.

Also there are other salts in water to consider. you can carry out precipitation reactions to remove them.

eg to make hard water soft (ie remove disoloved carbonate to form insoluble calcium carbonate) add calcium chloride

calcium chloride + sodium carbonate --> calcium carbonate + sodium chloride.

CaCl2(aq) + Na2CO3(aq) --> CaCO3(s) + 2NaCl(aq)

I dont know how the salts (minerals) affect CPs but I would have thought the only ones to be concerned with are the ones plants actually utilize such s those containing nitrogen, phosphorous and potassium, in other word nothing to do with carbonates. However, this is me just theorizing so Im not certain about this.

I dont even know if anyone has actually found out what exactly dissolved in tap water is harmful to CPs.

Its would make an interesting experiment to make up solutions of various salts in distilled water and apply then separately to individual plants to see the effect on growth

Edited by mantrid
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Calcium carbonate is very poorly soluble in water. Most calcium dissolved in water is in the form of calcium hydrogen carbonate. This is a lot more soluble than calcium sulphate, so in most situations some calcium sulphate will precipitate out when you add sulphuric acid.

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Ok thanks guys.

And Fred, I hear you there mate! I wander into the kitchen... pause... "Oh b#@@er!"... wander out and hope that I remember what I wanted in due course ;-)

I am guessing that we are still better of with rain water or some RO from the aquarium shop in emergency.

Cheers,

Steve

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