Water Quality: Hardness, pH, TDS. Where to draw the line?

[emmajs243]

Hey guys. My water is supplied from a well and I have been a tad concerned it may not be "orchid quality". Even more so, Cattleya seedling quality. (Idk if seedlings are specifically bothered by well quality water or not but i feel like I read somewhere that they might be??)

My water normally holds a TDS in the 450-480 range, pH seems to always be higher into the 7.45-7.60 range and besides knowing it is quite hard from the obvious signs, I am not sure the exact mineral content amounts....or how I could obtain this information. I have read you don't want your pH to be above 7.5 so there is my first concern. I also have read some saying that seedlings should be watered with water in a 6-6.5 pH range....is this accurate? I too feel like my TDS is quite high but honestly just don't know!

I pick up RO water regularly to always have on hand so I could dilute my water if needs be. I just hate to fertilize with pure RO water because I have read it is a lot easier to over fertilize due to the RO water not being buffered at all. Advice??

[aliceinwl]

Others can give a more detailed response. We have hard well water too and a reverse osmosis system for drinking water. I give the outdoor orchids hard water from the hose and the indoor orchids RO water. Everyone gets the same fertilizer. So far (~4 years for my oldest plants), all the orchids are fine. I steer clear of anything reputed to be finicky or delicate, but I have lots of Phalaenopsis, Phaphiopedalum, Cymbidium, Oncidium, Zygopetalum, various intergenerics, temperature tolerant Cattleya, etc.

[Orchid Whisperer]

My first suggestion is, if you are relying on inexpensive TDS and pH equipment, that equipment may not be accurate. This is especially true if the equipment can't be properly calibrated to reference standards. A TDS meter really doesn't measure total dissolved solids; the meter estimates TDS from electical conductivity (EC; also known as specific conductance, or just conductivity).

If you have this information from calibrated lab-quality meters, your data is more reliable. pH paper will usually give you a more useful pH value than a non-calibrated meter.

Many counties also have county extension offices, or water utilities, that may be able to do some water testing for you, or they can recommend a lab. A lab that does agricultural testing can do a range of useful tests at a moderate cost, often included in a water test for "irrigation suitability". There is a lab in Camilla, Georgia called Waters Agricultural Laboratory that can do such a test, there are many such labs across the USA (Waters Agricultural Lab is just an example).

If you have a water softener on the plumbing as it enters your house, it is important to test the water before it reaches the water softener (faucet on the well outside, maybe). Added later: you should also use water that has not been through a water softener to water orchids.

Also, it is important to know what type of Orchid you are growing. Many Phalaenopsis or Brassavola will be more tolerant of high TDS than a Paphiopedilum, for example.

Very generalized acceptable values:

Hardness: moderately hard or softer

TDS: 200 ppm or lower (depends on the minerals contributing to TDS)

pH 6.0 to 7.5

[Ray]

If you really want to know what is in your water, get it analyzed. For a nominal fee, J. R. Peters (the fertilizer folks in Allentown PA) will send you a bottle and give you a good plant-centric analysis.

I'd be less concerned about the pH than the TDS. Potting media and the plants themselves affect the pH at the root zone, so even if you're water is out of a preferred range, it doesn't mean that's what's the plant is living with.

Some plants may tolerate higher TDS than others, but are you trying to grow them well or merely scrape by? Orchids have evolved to use very pure water (rain), and definitely grow better if they are irrigated with low-dissolved solids solutions.

The "easier to overfeed using pure water" thing makes no sense. Add 100 ppm of fertilizer to pure water or water with 200 ppm solids and you're still providing 100 ppm fertilizer. What unbuffered water does affect (or really doesn't affect) is the stability of the pH, but again, that might not be an issue.

[emmajs243]

Thanks orchid whispered.! Ok so to end your concerns on equipment not being up to snuff I will expand. I actually work in a WET lab or water lab so although my equipment may not be super pricey, it is always calibrated to high quality standards also, I have done comparisons at work of my pH meter to the extremely pricey ones we use there and they are pretty spot on. TDS, well that's a different story because I work with wastewater, we don't test TDS. So although I do understand that they only measure EC and what not, I just can't do a comparison to really back up my meter past calibrating.

So I know, I am sure many of you are thinking, if she works in a lab why doesn't she just test it? Well I could for some things pretty easily, Nitrates, Nitrites, Amonnia, some heavy metals, e-coli, even total and ortho phosphorous and sulfides, past that, I really do not have the supplies to test minerals since we are a wastewater lab.

---------- Post added at 06:40 AM ---------- Previous post was at 06:37 AM ----------

Oh and we are talking some Cattleyas and Vandas (the vandals more just a future plan I would like to know for).

[emmajs243]

Thanks ray! And let me put it this way, if your going to do something half way, why even bother at all? Meaning, I definitely am trying to grow them well, NOT scraping by!! I really enjoy your attitude about rain water being what they have evolved to handle. That is an excellent point!

Also! Big thanks to commenting on the entire RO water being easier to over fertilize with comment! To me, as a scientists, it didn't make a lick of sense. In my mind, if anything, I would think it would be the opposite since their are unknown amounts of compounds within the well/tap water!

[Orchid Whisperer]

emmajs243, it sounds like you are all set in terms of lab equipment and testing. Since you have access to a wet lab, you probably have a good EC meter, you can calculate an estimated TDS from that, and also do a comparison check to be sure your TDS meterc is working properly.

I still recommend a basic water test if you can do. Here in Georgia, you can submit a sample to your county cooperative extension office, $20 gets you pH, hardness, and 15 metals and other elements. Such a deal! Your state probably has something similar.

Interesting that you work in a wastewater lab. For many years, I worked for a company that worked on the soil/geology/groundwater/wastewater part of land application system design. I now work for the state here, in environmental protection (regulator, re: site cleanup).

[emmajs243]

That is SUCH a great deal! I definitely would like to get a basic water analysis done. All have to check with county! As well as Rays suggestion! We have a lot of crop farmers out here so I would definitely guess we have a LOT of places that test water for plant use! I just hadn't even thought of that as an idea! I'll do some research!!

Also, thank you for the info on the EC meter! We definitely do have some so I will look into that!

But yes! We do all the wastewater for our city! Your just on the other side of things!!!

[Roberta]

I don't know how tolerant your Catt seedlings are (I tend to get larger plants), but more mature plants don't seem to care. My water is not as high in minerals as yours, Emma, but it's not great. But I know several people in my area whose water is a a whole lot worse than mine (a few miles inland, 500-600 ppm is common) and grow Catts quite successfully. I haven't found Vandas to be especially sensitive either. It's when you get into the Pleurothallids, also Phrags, and Sophronitis (yes I know they're now classed as Catts but they don't grow the same) better water is important.

Paphs are another group that does fine with hard water - The Huntington Botanical Garden in Pasadena uses well water that ranges from 200-800 ppm TDS (we're talking mostly Calcium Carbonate in southern California) on their world-class Paph collection (RO is used for those orchids that actually need it)

pH affects how much of nutrients in fertilizer are actually available to the orchids. Before I got my RO system I used vinegar to bring the pH down to 6.5 or so in the fertilizer water, otherwise everybody got tap water, pH about 7.8, (classic calcium bicarbonate) and the Catts and Cyms still get that city water to no ill effect, just get RO when I fertilize.

[emmajs243]

Thank you Roberta!

It definitely would be a lot more efficient to not have to water EVERYBODY with RO water. Right now I'm just using it in my humidifiers so I don't have the white dust of minerals all over my house and on my New Cymbidium because she has some brown leaf tips that seem to be from over fertilizing/mineral build up.

Obviously, the seedlings take substantially less water so those guys wouldn't be nearly as bad to do a half and half mix of RO and tap water to start just until they adapt to it...IF that's even necessary....

I was pondering it tonight and decided that since I'm not positive, I'll check C&H's website to see if they specify and if not, I'll probably do like I would do with changing a dog food and bring it down to a more common range to start by mixing my well and RO water and try easing them up once they become acclimated to their new environment! That way, if I start seeing them not doing so well I can more easily pinpoint if it was the water or not. Or at least that's my hope!

It definitely would take quite a few more gallons of RO water every week to water ALL of my orchids though!