EDTA to remove scales in Coffee Machine - Use of EDTA to remove scales from Coffee Machine (Oct/17/2010 )

I wish to use EDTA (Ethylenediaminetetra acetic acid) to remove lime scale formation inside my coffee machine on a monthly basis as a way of maintaining the machine. Unfortunately, I live in a place where the water is hard. A water softener which is installed is but of little help.
I tried to dissolved EDTA crystaline powder by heating it in water. This proved to be impossible to do. I read somewhere that EDTA will start to dissolve with the addition of sodium hydroxide. My question is: How much EDTA, NaOH and water and at what temperature range should the dissolution be done? The coffee machine's water storage tank has a capacity of 2 liters, so the question also arises as to how much EDTA to do to fill the tank to capacity with the recommended descaling solution?

The coffee machine has a descaling feature wherein it circulates within its system the water from its storage tank containing the descaling solution, then expels it and
subsequently asks for a fresh full tank of regular water to flush out whatever traces of descaling liquid is left within. After that's done, it asks to have its storage tank refilled with fresh water before allows the user to make coffee again.

EDTA dissolves only at pH 8. otherwise it won't dissolve.

I wonder which use the EDTA should have anyway: before it can chelate the metal-ions, they have to be dissolved again. Calcium and magnesium carbonate is barely soluble in water or an EDTA solution and the coatings are often rock-hard. You can use EDTA to soften the water before heating it up to avoid limescale buildup. But then I won't drink it anymore...
Better use citric acid from time to time, it's cheaper too.

hobglobin is right, acidic environment makes the job in few minutes. Vinegar also could be used, but in a coffe machine I will not use it to preserve the aromas.

Interesting. possible just cut a few pieces of lime and wipe the surface?

adrian kohsf on Sun Oct 17 16:20:55 2010 said:

oops, we all misunderstood the problem: he wanted to control the scale insect infestation on a lime tree that grows in the coffee machine...

hobglobin on Mon Oct 18 16:48:50 2010 said:

Ok guys, forget lime or vinegar and use pepsi, it's strongly acidic, contains caffeine, it is the perfect coffee machine cleaning liquid.

Yeah... I had heard in some urban legends myth that Coke or pepsi can be used to clean toilets... LOL

Thanks for your thoughts everybody! Man, I love this forum!!!!