Can I use Vancouver tap water with semi-hydro?

[spinrah]

I’d like to do a trial with a new orchid in semi-hydro and I’m wondering if my tap water is pure enough to use instead of purchasing RO water? People always say that Vancouver has the purest water because it comes from rainfall and snowmelt. Heck, I only drink tap water because apparently Nestle was bottling our water and selling it back to us (no idea if that’s true). So I’m wondering if it’s safe to use our tap water for an orchid in semi-hydro?

Unfortunately I have absolutely no idea how to read this water report so I am hoping you kind folks can help me out.

https://vancouver.ca/files/cov/water...eport-2019.pdf

Edit: I also found this one which has a physical and chemical analysis in the Appendix. Not sure which is more useful. http://www.metrovancouver.org/servic...rt-Volume1.pdf

[early]

Originally Posted by spinrah

I’m wondering if it’s safe to use our tap water for an orchid in semi-hydro?

Unfortunately I have absolutely no idea how to read this water report so I am hoping you kind folks can help me out.

https://vancouver.ca/files/cov/water...eport-2019.pdf

I have well water and only adjust the pH for my orchids. Your tap water in the report states greater than 7.0 which would need to be acidified to make it safe for orchids. I use between one half table spoon to one tablespoon white vinegar to bring it down to 5.5 to 6.5 because of the calcium in the water. I am a new grower, past 18 months, and my orchids do well with that, I also add 1/4 tsp of fertilizer with 20-20-20 of N phosphoris and K . a pH ,meter is cheap on Amazon

[estación seca]

The brief answer is yes, you can use your water. I would check and adjust the pH after adding fertilizer to your water. Many people think pH test paper strips, or a pH test kit from a swimming pool supply or aquarium store, are more accurate than cheap pH meters.

[spinrah]

Okay, thanks to you both. So it sounds like the issue with my water is not its purity (i.e., it is considered "soft"), but that its ph may be too high?

Any special considerations I should also know about if using LECA? I am planning on using Hydroton brand.

[Roberta]

That water quality makes me jealous... that's not much higher than what I can achieve WITH my RO unit. ( 15-40 μS/cm is REALLY pure. pH is not much over 7 - fertilizer will tend to lower it, especially since there is very little in the way of minerals. ) I think that a pure-water formulation for fertilizer (like MSU Cal-Mag) would work well for you.

[thefish1337]

Your water is perfect. I have very similar water in the PNW, great out of the tap it just needs acidification as another poster mentioned. I didn't check pH of my low TDS high pH tap water for 5 years and my plants grew fine, but some of the more calcium needy plants suffered over long periods of time. Additionally your fertilizer may drop the pH into the right range without you having to do much, so make sure you check that before you start messing around with pH adjustment. if your fertilizer puts the pH between 5.6-6.5 you're golden.

In my experience I got better plant growth with "pH down" products versus citric acid or vinegar. It's not to say they wont work they're just not the best. "pH down" products are a combination of phosphoric acid, citric acid and ammonium. Vinegar and citric acid are rapidly consumed by microbes as a carbon source- my experience with using them for flood and drain hydroponics is that in less than 24 hours the pH will swing back wildly. Promoting bacterial growth in this way can be both good and bad. Plants like consistency so whatever you do just try to keep it consistent and even if you aren't perfect the plants will do well.

[Roberta]

Just remember, with such a tiny amount of solids, there is no buffering capacity of the water. That is why any treatment will make the pH fluctuate wildly. So be very cautious about messing with the pH. If you measure it, measure after it has run through the plant container, not out of the tap, to establish what the plant is actually getting. If you use a fertilizer like MSU Cal-Mag, you should not have to do anything - and will also be adding a supplement of calcium and magnesium, which are likely needed since the water has hardly any.

[spinrah]

Thanks so much! I feel so lucky to have such great tap water. I am using k-lite fertilizer, which I think is similar to MSU? So I’m thinking I should be fine. But maybe I will check the pH after adding fertilizer just to be sure.

---------- Post added at 05:24 PM ---------- Previous post was at 05:22 PM ----------

thefish, do you have any advice for using semi-hydro in our climate? I’m just growing in my home - no fancy greenhouse or temp control, so I’m worried about evaporation.

[Roberta]

I think more important than worrying about the pH... if the fertilizer doesn't already include a cal-mag supplement, consider adding that to your regimen.

[thefish1337]

Originally Posted by Roberta

Just remember, with such a tiny amount of solids, there is no buffering capacity of the water. That is why any treatment will make the pH fluctuate wildly. So be very cautious about messing with the pH. If you measure it, measure after it has run through the plant container, not out of the tap, to establish what the plant is actually getting. If you use a fertilizer like MSU Cal-Mag, you should not have to do anything - and will also be adding a supplement of calcium and magnesium, which are likely needed since the water has hardly any.

This is not accurate.... the pH of the Vancouver tap water is treated both to increase alkalinity (as per the report) and raise the pH to prevent harmful leaching in pipes. It's pretty well buffered or else much more harmful effects of old plumbing would be observed. I also don't agree with the idea of adjusting pH to the leachate, but that's just like, my opinion, man.

I have used MSU (RO/Well) and K-Lite (RO) with very similar water and because they are low P and mostly nitrate nitrogen they will not drop the pH nearly as much as you are claiming. The well water version offers more ideal pH adjustment but it lacks calcium and magnesium because it assumes your water has it. Our water has a little calcium and no magnesium and low TDS so the RO versions offer the more complete suite of nutrients, however, like I said before they don't drop the pH very well. Basically no one makes a perfect fertilizer for this type of water but its possible to make it work easily:

1) use the well water MSU formula and add a little epsom salt in every so often
2) use the RO version of MSU/Klite and acidify properly
3) use any 20-20-20 or 30-10-10 fertilizer + a cal-mag supplement

I'm sure someone will eventually come along in this topic and mention how plants will change the pH of their root zone and so it doesn't matter. But that's a separate argument that only proves that orchids are tolerant/adaptable (they are, literally no one is debating this) and doesn't address anything if a grower is looking to optimize their culture.

In my experience, running with very similar water as OP and with multiple species in semi-hydro, and testing out many different formulas, I got better results with proper pH adjustment. However, my experience as well as other contributors in this topic also shows that plants will do just "fine" if you don't really worry about pH that much.