Lowering pH of Water

[Deltron]

I think some of my caudiciforms may have suffered at the hands of (slightly alkaline) tap water when reliable sources suggest that lower pH's (as low as 4-4.5) are favoured by some species such as pachypodiums. I don't have rain water access via a water butt.

Does anyone have a safe and tested way of lowering pH regularly when using tap water as source? I have seen Hydroponic solutions but these are costly and therefore I was hoping to avoid.

Any advice and experience would be appreciated - thanks...

[iann]

Add acid. How much depends on how hard you water is. Get a cheap test kit or some universal indicator strips and see how much of your preferred acid it takes to drop the pH. Then that's how much you need. Maybe re-test every few months in case you water supply changes with the seasons.

[esp]

There's plenty of stuff on't web about using vinegar or acetic acid for small scale water acidification.

FWIW, don't many Pachypodiums come from limestone areas?

[Eric Williams]

Until I installed water butts to collect rain water, I used the following well known formula for many years without a problem. One teaspoon white vinegar into one gallon of tap water. Test with litmus paper if required.

[iann]

Until I installed water butts to collect rain water, I used the following well known formula for many years without a problem. One teaspoon white vinegar into one gallon of tap water. Test with litmus paper if required.

Yes, but you were either lucky or it didn't make a blind bit of difference. The amount of vinegar needed to acidify hard water and soft water is orders of magnitudes different. One size doesn't fit all, despite what the vinegar marketing board guerilla advertising says.

[jfabiao]

Add acid. How much depends on how hard you water is. Get a cheap test kit or some universal indicator strips and see how much of your preferred acid it takes to drop the pH. Then that's how much you need. Maybe re-test every few months in case you water supply changes with the seasons.

If I may add something, make a confirmation test a few hours - a day, maybe? - after the first one, to make sure the pH does not bounce back (which it usually does).

[FredG]

You could buy a RO (Reverse Osmosis) filter and a TDS meter. They're made for purifying aquarium water. The meter will indicate Total Dissolved Solids ie. purity.
pH meters are also very reasonably priced these days if you decide to go the Acid method. Many, many years ago I used Sulphuric acid to lower the pH of tap water for use with my Carnivorous Plants in a drought.

[edds]

Is the important thing with water the pH or the hardness with Cacti?

My experience is much more with orchids than cacti but with orchids the key is low total dissolved solids water and dilute fertiliser, pH is not very important.

So is pH or TDS the important factor?

[gerald]

By TDS do you mean EC?

Desert cacti are often found near salt flats, and arid environments create high salt environments due to so much evaporation. So I would have thought a high EC soil would be the norm. This is just a guess though!

This is interesting reading on pH, all you will ever need to know, and more:

https://www.rrm.me.uk/Cacti/Cactus%20an ... linity.pdf

"The harder to grow genera that seem to love limestone,Ariocarpus, Escobaria, Turbinicarpus, and other genera do not grow when given alkaline water, but will immediately start growing when given acidic water. "

[edds]

By TDS do you mean EC?

Desert cacti are often found near salt flats, and arid environments create high salt environments due to so much evaporation. So I would have thought a high EC soil would be the norm. This is just a guess though!

This is interesting reading on pH, all you will ever need to know, and more:

https://www.rrm.me.uk/Cacti/Cactus%20an ... linity.pdf

"The harder to grow genera that seem to love limestone,Ariocarpus, Escobaria, Turbinicarpus, and other genera do not grow when given alkaline water, but will immediately start growing when given acidic water. "

TDS is the total dissolved solids whereas EC is the electric conductivity which only measures conductive elements. In reality the TDS meters we use are measuring EC and then using it to estimate TDS so while they shouldn't be the same they are often analogous to each other!

Good point on the environment of cacti - for orchids they are usually epiphytic and being watered by regular rainfall so very low TDS environments where nutrients are in very low supply and so they have evolved to make the most of them and too much potassium especially seems to build up in the potting media and reduce or even stop root growth.

I wonder whether many cacti might actually get softer water than we think in their environment while growing but are more tolerant to higher nutrient levels than many other plants due to the dry periods when evaporation would lead to an accumulation of salts in the soil as you suggested? It could be a very different ionic environment from dormancy, start of good growing conditions to the end of them before re-entering a dormant period.

I will give that article a proper read later - thanks for the link.