Why do I still have mineral buildup?
 

I recently made the conversion to using R/O water for watering. At my old house the water was extremely hard, and left mineral buildup very quickly. My hope was that using R/O water would negate (or at least minimize) this problem.

I have a little paph seedling (it said it was "near blooming size") in S/H. When I saw it was getting the buildup even with R/O water, I repotted it with brand new LECA. But the mineral/salt buildup came back! How come I'm still getting this buildup? I'm concerned it might damage the roots on this little paph.

First, RO water does still have some minerals/salts, just much less than your unfiltered tap water. My RO system gets rid of 90-95 percent according to my TDS meter, but there is still some in there. I had the same problem as you when I first tried S/H and also got an RO system. I'm definitely no expert on SH, but here's what I did and it seems to be working so far:

I rinse and drain the LECA for about a week before using, rinsing and draining every night to get out any salts in the media.

Flush the pots ALOT with unfertilized water on a weekly basis.

Mine are now in terrariums with humidity around 75% - the media now stays more moist longer.

I have no idea if any of the above will work for you, but it works for me in my environment.

Have you ever tested the product water for tds?

Thanks for the quick replies! I forgot to mention that I am flushing frequently with plain R/O water, which is partly why I was confused.

Subrosa, I haven't checked the tds in a while--I should probably do that. The system was brand-new when we built the house, so I don't think it's time for a filter change, but it could be! Once fertilizer is added, what is a good tds to shoot for?

0 is nice, but not always practical to achieve. Consider that most ro systems are 98% to 99% efficient. In other words if the water entering the system has 100ppm tds, the product water wil have 1 or 2 ppm. My tap water runs closer to 200ppm, and I know of folks on private wells whose water measures well over twice that high in tds. Typical one membrane systems won't give you 0 tds with input water like that. Without knowing the tds of the source water it's impossible to determine how well the membrane is performing.

It could be manufacturing residues in the LECA.

• The starting clay is not pure.
• Then add chemicals to bind the particles together and others to literally take up space in the pellets to create pores.
• Fire the pellets.

The additives and impurities in the clay - both organic and inorganic - can react with the additives and form soluble salts that reside throughout the pellet. As you water, they dissolve, are transported upward, and deposited when the water evaporates.

I hope you get this solved. We have a water softener so our water is unusable. I always envy the people that just water under their tap without any problem at all. :|

Couldn't you run a water line from before your water softener to a tap you could use? Do you use this softened water to drink and cook? It may have a great deal of sodium in it.

If you have an outdoor hose bib it likely is supplied with pre-softener water.

No, everything here runs through the water softener. The main waterline goes directly to the water softener before branching off. With the water we have, that is actually a good idea. :|

Theoretically, the salt and calcium combine and you shouldn't be consuming that much salt. Still, yes, that is something that we do worry about. However, I grew up getting my water from the Ohio river and that water was pretty bad (though it wouldn't hurt the plants, I think, just killed off my fish now and then) so I see this as an improvement.