Can I use Vancouver tap water with semi-hydro?

[spinrah]

Originally Posted by thefish1337

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.

This is great information, thank you. Do you have a preferred treatment for altering pH? Maybe a specific brand of product you use?

[thefish1337]

I have a generic version I got at the hydroponis shop, however a popular brand is general hydroponics "pH down".

[spinrah]

Originally Posted by thefish1337

I have a generic version I got at the hydroponis shop, however a popular brand is general hydroponics "pH down".

Awesome, I should be able to find that at the hydroponics shop close to me. Thanks again for all your help.

[Ray]

1. I have no idea why folks think RO is necessary for S/H growing. If your water is OK for traditional culture, it’s fine for S/H. Sure, purer is better, but that’s universal.
2. The average pH level is probably fine, as-is. 5.5-6.5 is what I shoot for, but +/- a full unit is still OK.
3. The applied solution pH is far less important than what happens in the pot. Before you go making adjustments, do this:
   • Water the plant thoroughly with your plain water.
   • Wait 30 minutes to let it drain thoroughly and chemically equilibrate.
   • Trickle about 50 ml of PURE water over the medium and collect the drainage.
   • Test the pH of that.
   • Repeat using your fertilizer solution. It probably won’t be a whole lot different.
4. Be wary of “pH Down” products. Most are phosphoric acid, and there have been examples of long-term phytotoxicity with its continued use.

[spinrah]

Originally Posted by Ray

1. I have no idea why folks think RO is necessary for S/H growing. If your water is OK for traditional culture, it’s fine for S/H. Sure, purer is better, but that’s universal.
2. The average pH level is probably fine, as-is. 5.5-6.5 is what I shoot for, but +/- a full unit is still OK.
3. The applied solution pH is far less important than what happens in the pot. Before you go making adjustments, do this:
   • Water the plant thoroughly with your plain water.
   • Wait 30 minutes to let it drain thoroughly and chemically equilibrate.
   • Trickle about 50 ml of PURE water over the medium and collect the drainage.
   • Test the pH of that.
   • Repeat using your fertilizer solution. It probably won’t be a whole lot different.
4. Be wary of “pH Down” products. Most are phosphoric acid, and there have been examples of long-term phytotoxicity with its continued use.

Great, thank you. I was wondering whether the media inside the pot also affects the pH, so your method makes a lot of sense.

[Ray]

Originally Posted by spinrah

Great, thank you. I was wondering whether the media inside the pot also affects the pH, so your method makes a lot of sense.

The medium, the plant, and the microbes populating them all affect it.

In theory, LECA should be inert...

I used to be very conscious of my applied solution pH, then learned more about the in-pot reactions. I have applied stuff as low as 4.0 and the pour through was still in the acceptable range.

[Orchidtinkerer]

I use ph down from the hydroponics store.
There might be downsides, you can find downsides to everything from paracetamol to dishwasher liquid.

thefish already mentions that citric acid is not stable and degrades.

I can find plenty of negatives of citric acid which would make me avoid it altogether, for example ( you have to scroll half way down the article where it talks about citric acid, the rest is about acid rain which is not relevant)

Garden Guides | The Effects of Smog on Plants

[thefish1337]

Originally Posted by Orchidtinkerer

I use ph down from the hydroponics store.
There might be downsides, you can find downsides to everything from paracetamol to dishwasher liquid.

thefish already mentions that citric acid is not stable and degrades.

I can find plenty of negatives of citric acid which would make me avoid it altogether, for example ( you have to scroll half way down the article where it talks about citric acid, the rest is about acid rain which is not relevant)

Garden Guides | The Effects of Smog on Plants

Yeah, I think its a bit misleading to scaremonger with phosphoric acid. Maybe relevant advice to people with high TDS tap/well where they have to use loads of it but I'm adding 10-20 drops per gallon (<0.5mL) to get my pH in range. pH down wouldn't be the right solution with that type of water (or cost effective).

In this specific type of water the amount of phosphates from the pH down are incredibly small and are diluted many orders of magnitude.

[Ray]

No scaremongering intended. Certainly any issues will come about from prolonged, excessive use, not minor adjustments, but it does pay to be aware of possibilities.

Citric acid is not much of a concern. It is often added to fertilizers to enhance solubility.

[Clawhammer]

Does anyone "rest" their water? My tap water (super pure PNW water) comes out of the tap between 7.5-7.8 before ferts. After resting 24 hours with aeration it is around 6.8 before ferts as CO2 is removed from the water by aeration. This effect is larger during the cold months as cold water absorbs more CO2.