TDS water level for P. rotschildianum, P. philipinense, and P. St. Swithin

[jantigercat]

Hello all!

I would like to know what is the recommended TDS level for P. Rothschildianum, P. Philippinense and P. St. Swithin. The TDS level on our tap water in the city is around 320 ppm. Would that be too much?

[Roberta]

In various talks to societies, and also in Orchids and Orchid Digest, Brandon Tam, the orchid specialist of the Huntington Botanic Gardens in southern California, has noted that they have found that their Paphs (one of the biggest collections in the US) actually do BETTER on well water that ranges from 200-800 PPM TDS than with RO water. This is southern California water, high in calcium carbonate. So high TDS (and associated high pH) is not particularly a problem for Paphs. If the TDS is due to sodium, that could be an issue... so you need to look at the water analysis that you should be able to get from your water provider. Other orchids are much pickier about pure water (like many cloud-forest types) but Paphs seem to be a group that is not fussy. (Same is not true of Phrags... those tend to prefer more pure water)

[estación seca]

You can read notes of Brandon's talk to the Desert Valley Orchid Society (DVOS) on how he grows Paphs. Use Advanced Search to search on "Tam" and my partial username "estación seca" - note the search requires the proper diacritic.

I have grown a Paph. rothschildianum seedling with my water having 800-1200 parts per million total dissolved solids. It didn't seem to mind.

[King_of_orchid_growing:)]

I will note, the TDS value is rather nebulous.

As was mentioned, it varies in usefulness depending on what minerals are in the water.

The term Total Dissolved Solids (TDS) describes a broad range of minerals dissolved in water.

It is more important to note that it is a better reference to know how much dissolved calcium carbonate in the water is beneficial to these Paphs - not necessarily the TDS. A lot of Paphs grow along the cliff faces of limestone formations in the wild.

There are aquarium test kits that can help measure dissolved calcium ions in freshwater (they're often marketed for use in saltwater aquariums, but they're interchangeable depending on brand and chemicals used).

[estación seca]

Almost all dissolved solids in the US are calcium and magnesium carbonates. One can read the annual water quality report found online at the water utility to find this information.

[Ray]

Originally Posted by estación seca

Almost all dissolved solids in the US are calcium and magnesium carbonates. One can read the annual water quality report found online at the water utility to find this information.

if only...

Unfortunately, that's not universally true. The water quality reports required for publication in the US relate to safety, so bacterial loading, heavy metals, and some toxic chemicals may be listed, but way too many of them don't tell you a damned thing about the minerals we would like to know.

[jantigercat]

Ive searched for the quality report of our water supply here in Mannheim and the sodium level is 29.4 mg/l. Is that ok? Or is it too high?

[Roberta]

At any rate, the TDS given by the OP doesn't look bad by any definition unless they live by the ocean making sodium an issue. By my standards, that level looks pretty good, suitable for just about everything except sensitive cloud-forest orchids. Certainly better than the "liquid rocks" common in my part of the world,

---------- Post added at 03:09 PM ---------- Previous post was at 03:05 PM ----------

Originally Posted by jantigercat

Ive searched for the quality report of our water supply here in Mannheim and the sodium level is 29.4 mg/l. Is that ok? Or is it too high?

That doesn't look bad. The majority of the TDS is probably due to calcium and magnesium, which are fine,

[King_of_orchid_growing:)]

Originally Posted by estación seca

Almost all dissolved solids in the US are calcium and magnesium carbonates. One can read the annual water quality report found online at the water utility to find this information.

Assuming this is true ...

Using the value of your TDS meter, what is the ratio of calcium to magnesium present in the water? (This is kind of where most people stop. I don't know how likely many people would bother to check their water breakdowns. Most people just take the reading of their TDS meter at face value and call it a day.)

Would that TDS also account for lead? If yes, how much does it contribute to the TDS value?

Would the TDS value account for copper? If yes, how much?

How about any other "solid" dissolved in the water that makes up that "total"? (Remember, TDS = Total Dissolved Solids)

Get it? The answer to all of these questions is a big fat - "I don't know."

And if you do get the breakdowns, like Ray had said, there'll be more than just calcium and magnesium carbonates/bicarbonates.

At the end of the day, using a TDS meter to get TDS values isn't necessarily detrimental to orchid growing, but neither is it all that useful, in my opinion.

Originally Posted by jantigercat

Ive searched for the quality report of our water supply here in Mannheim and the sodium level is 29.4 mg/l. Is that ok? Or is it too high?

The sodium level of 29 mg/L is fine. It isn't going to cause an issue.

[Roberta]

I'd say that if lead or copper were high enough to significantly add to the TDS, the water would be classed as toxic waste... At least in the US (and I think the EU is even more strict) the limit of lead in drinking water is in the low parts-per-billion range, copper around 1 ppm.