Alex Woodward wrote:

"Chris Hogg" wrote in message
...

On Tue, 14 Jun 2005 20:15:29 GMT, "Alex Woodward"
wrote:

Is there an easy way to turn limey tap water into acidic so that I can
water
my heathers.

I add a teaspoon (say 5 ml) of vinegar to a 7 litre watering-can if
I'm watering ericaceous plants with tap water. It brings the pH down
to about 5. Our tap water is pH 7.5, not because we are in a chalky
area, quite the opposite, but many water companies add lime to raise
the water pH and reduce corrosion of concrete tanks and pipework, and
to assist in clarification of the water. I use vinegar because, as a
weak organic acid (in the chemical sense, not the eco-friendly sense),
it's broadly similar to the acids already present in peaty or acid
soils, but a single drop of battery acid would probably be just as
effective!

Adding sulphuric acid would be marginally more effective since calcium
sulphate is much less soluble than the acetate. Calcium fluoride is
virtually insoluble but you could easily get yourself killed handling HF
acid. It likes calcium far too much...

Calcium in th water itself isn't harmful to heathers (or other
ericaceous plants, for that matter), but the high pH associated with
chalky soils or limey tap water means that certain trace elements,
notably iron and manganese, are rendered insoluble and unavailable to
the plants. Some plants (and some types of heather, especially the
winter flowering types) are quite happy in these conditions, as they
don't have a high requirement for iron and/or manganese, but most
ericaceous plants do, so their leaves become chlorotic (yellow) and
they fail to flourish. Watering occasionally with limey water probably
won't do any harm, but repeated watering will eventually raise the pH
of the soil, or more particularly compost if it's a potted plant.

Thanks for an extremely informative post Chris. I'll definitely try the
vinegar tip. I'll use1 teaspoon full of vinegar as you suggest and give it a
PH test. So obvious when I think about it now, but it really did not occur
to me. Thanks again.

He has answered your question in a strict sense. Adding vinegar will
lower the pH, but since calcium acetate is soluble and calcium carbonate
is not you will gradually clog up all the pores in your compost. The
plant roots will eventually suffocate - only a matter of time.

Proprietory feed mixes like miracid that stabilise the unwanted calcium
salts in an organic complex are much better if you must use limey
tapwater. But the simplest option by far is to use collected rainwater
for lime sensitive plants.

Regards,
Martin Brown