Water TDS level

[Roey.P.]

In my city there is 300 TDS in tap water which my orchid been having for half a year and are growing EVEN BLOOMING just fine. The nursery near me use those tap water too. And told me that distilled water are not as rain water and not healthy to the plant as not for us. And I have other carnivorous plant that must have untill 100 TDS so I use rain water with 18 TDS.
THOSE anyone ever check for tds or check now for comparing thanks in advance for your help!

[Ray]

I don't think that TDS, by itself, paints the whole picture. WHAT those dissolved solids are plays a role, as does the tolerance level of the plants, as you pointed out.


Ray Barkalow (via Tapatalk)

[tropterrarium]

There is also the issue of what orchids you grow and how you water them. If you drench them every time, you won't have any salt build up. If you are a stingy waterer, you may get salt build-up.

Then there is fertilizer. That adds to osmolarity of the city water. Do you fertilize every time rather weakly, or are you fertilizing once in a while with a burst?

AFAIK, TDS of 300-350 is about the max that most orchids can take with fertilizer. If you fertilize full strength, you will easily top that by a good margin. If you fertilize weakly (<1/4 strength), you may be within tolerance levels.

If you have healthy plants that bloom, all seems to be fine.

Distilled water is certainly tricky. The stuff you get at the grocery store is pretty clean, but not chemically pure water (you can get that from Sigma, and it will cost ya). After TDS, the next parameter that is fairly easy to assess is pH. pH of water and pH of water plus fertilizer are often not the same, even with the specially formulated versions (RO fertilizers). My RO water is pH 6.3, with 100 ppmN K-lite RO it is about 4.5, so have to adjust with KOH (oviates the K-lite idea, but I have a bunch of it; alternative would be NaOH).

What many people do is blending tap with pure water (RO, DI, distilled) to cut down on TDS, but still have some pH buffer capacity. That may be a relatively easy way to see whether you have a problem with your tap water TDS level.