Flushing with tap water

[Ray]

That electrical conductivity is quite low, so I would probably continue with the Rain mix to ensure a decent calcium content.

I suspect it will lower your pH a little bit too.

[marcoeverard]

Thank you both for taking the time to give me such in-depth answers I think I am starting to understand this a bit better now. Actually re I have just about finished my tub of rain mix so had bought some orchid Focus grow not sure how that will affect things. I have also bought some seaweed fertiliser and was going to use that once a month as you suggest to try and stimulate the root growth.

[marcoeverard]

Originally Posted by Ray

That electrical conductivity is quite low, so I would probably continue with the Rain mix to ensure a decent calcium content.

I suspect it will lower your pH a little bit too.

Hi again Ray. I have spent the last couple of days fitting some more water Butts to collect rainwater and so now should have plenty. I also bought a ph and TDS pen and I am wondering if you could tell me if I am on the right track please. The rainwater in the water butt has a pH of 7.6 however when I mix a watering can of rainwater with one very small spoon of rain mix I get a pH of 6.5 and a TDS reading of 85 PPM. So if I was to to feed and flush with that solution once a week leaving the water in the reservoir and every third or fourth week flush with just plain rainwater does that sound right?

[DirtyCoconuts]

I think you can skip that fourth flush and just always use that feed strength as your water

[Ray]

I agree with DC, with one caveat: don’t just automatically trust the TDS meter to give you accurate readings. Read this.

Assuming the water is pure (with a pH of 7.6, it’s not), a true TDS of 85 ppm with Rain Mix would be about 10-12 ppm N. Because there is already something in the plain water, the fertilizer concentration is lower. I know some folks that view that as an appropriate nitrogen level, but I prefer something in the 20-25 ppm N range.

[marcoeverard]

Thank you both. Yes there is something in the rainwater which I guess is due to the occasional leaves etc that get in there and whatever else is on the orchid house flats roof where the water is harvested

[Ray]

Originally Posted by marcoeverard

Thank you both. Yes there is something in the rainwater which I guess is due to the occasional leaves etc that get in there and whatever else is on the orchid house flats roof where the water is harvested

...and what it absorbs from the air.

[monivik]

Originally Posted by marcoeverard

Hi. I am brand new to semi hydro and have done what I was warned not to and connverted almost everything to semi-hydro. My orchids have been struggling and seem to be either too dry or too wet so I thought I didnt have much to lose. The Phrags are already showing good root growth after a few weeks so at least they like it. I am wondering if it is ok to fluh the pots regularly with tap water which is a little on te hard side and then flush with feed and rainwater every 4th or 5th time? I don't have enough rainwater to use just for regular flushing so either I need gto use tap water or get a RO unit and i would rather not at least until I see how they are doing? Sorry if this has been asked before but I couldn't find an answer I love the idea of S/H as I am not always at the orchid house property and being able to leave them occaisonally with a reservoir of water will suit my lifestyle. Any suggestions on what feed to use would be great too. I am in the UK and have been using rainmix but wonder if something else would be better if they are not being fed at every watering.

Hi. This has nothing to do with S/H, but you asked about watering and using hard tap water. Well, I don't know if you've seen this video? But I think it's quite interesting, because this guy waters all his orchids with hard tap water. He also uses fertilizer.

[WaterWitchin]

My personal opinion of Here But Not Here... he's full of hot air and misinformation. He speaks in a lot of "absolutes" that clearly contradict each other. As Roberta has said in other settings, he has a lot of "always" and "never" attitudes. He's the kinda dude that likes to listen to himself talk, but doesn't have much helpful to say.

Harsh? Perhaps. His video on semi-hydro just makes my blood boil... or maybe it's his blog. Either way... yuck.

Oh, and what Ray says... doesn't appear on any subject to take into consideration different climates, environments, culture, etc. That's never helpful, especially to those trying to learn.

[Ray]

Originally Posted by monivik

But I think it's quite interesting, because this guy waters all his orchids with hard tap water. He also uses fertilizer.

Don’t overlook the fact that not all “tapwater” sources are the same.

NYC water is about as close to pure as you’re going to ever see. It typically runs from 30 to 50 ppm. My water here in southeastern NC is typically about 60 ppm, but then they add about 50 ppm calcium.

By contrast, the municipal water we had when I lived outside Louisville KY was known locally as “liquid concrete”.