Adding HCl to top up water

Jackfrost

My tap water is quite alkaline and each time I top up my FT I am moving the pH up above the level that plants can take in nutrients. I am going to start adding HCl to my top up water before adding it to the FT to avoid this bouncing around of pH.

Good idea? Bad idea?

Does anyone have a formula for how much I should be adding to 20L of water at 7.6 to bring it down to 7.0?

werdna

The nitric acid produced by the nitrogen cycle will bring your ph back down.
There is no set rule for how much acid to add, just remember hcl is a strong acid, so you wont need much.

Best thing to do would be fill up a 20L container with your water, keep adding acid until you get the ph you want, then just add that much every time.
But 20L wont need much acid, add no more than around a qtr of a teaspoon at a time.

Edgewateraqua

Ive been using hydroponic ph down in my top up water for the same reason. The (hydroponic) ph down is phosphoric acid which only needs to be added at about 1ml or less to get the ph from around 8.2 to 6.8 in 10L of water in my small blue barrel system. Plus it adds some phosphorous to the system which most of the plants love. You can get a small bottle of it from bunnings for under $20 if i remember right.

Mr Damage

Quote:

Does anyone have a formula for how much I should be adding to 20L of water at 7.6 to bring it down to 7.0?

I’m N.O.R. and only a couple of k’s from you, so I would imagine our water should be similar. I know if I add 1/2ml of HCl to a 10L watering can it brings the pH down into the low 6’s, but I like to add 3/4ml to the 10L, it takes the pH down to around 5.8

When treating your top-up water it’s desirable to get it down at least into the low 6’s, at that level the acid will consume the carbonates, therefore reducing the waters ability to buffer the pH up.

earthbound

Personally I wouldn't be worrying about it, you'll find that in the near future your pH will be coming right down anyway.

Jackfrost

Cheers guys such small amounts gives me a good reference point

Jackfrost

earthbound wrote:

Personally I wouldn't be worrying about it, you'll find that in the near future your pH will be coming right down anyway.

Not from my tap it won't be…

earthbound

Yes but your system water will be going down, so adding top up water with a slightly higher pH will be a good thing.

Mr Damage

My kid's single blue barrel system is over twelve months old, the pH in the first few months was always around 8.0+, I've been treating the top-up water with HCl acid for about 7 or 8 months now, and I've been adding around 20L to the 70/80L system per week during summer, the treated water has been maintaining the pH around 7.5/7.6... if I stop treating the top-up water, the pH in the system is back up to around 8.0 within a week.

earthbound

You should stop testing your water...

Mr Damage

When the pH is up around 8.0-8.2 the plants look decidely average and growth is slow. When I keep the pH down around 7.5-7.6 by treating the top-up water...the plant health/growth is much better.

I don't test much since it cycled over twelve months ago... Amm, N02, N03 very occassionally, but only if I can see an issue, or I've made some sort of change/addition to the sytem... and pH about every 2-4 weeks now... because I've been playing the same game with this system for over twelve months now, I know what the results are going to be.

I'm waiting for that magic day when I test and the pH has actually dropped... then I'll stop treating my top-up water, but until then my plants are much better for it, and it's not difficult to add 3/4ml of acid to a watering can when filling it up.

The first AP system I ever built did the same, it ran for about 10 months before I dismantled and sold it. In that time the pH never dropped below 7.5-7.6... and that was with the addition of HCl... without HCl it would get up to 8+.

I know everyone says be patient, the pH will drop, and I've seen it drop in systems after a few months, but I've had two systems where the pH has refused to drop, and in that situation I can't see a problem in reducing the carbonates in the top-up water prior to adding it to the main system... if it helps keep the pH in the mid 7's and keeps the plants and fish healthy.

Jackfrost

earthbound wrote:

Yes but your system water will be going down, so adding top up water with a slightly higher pH will be a good thing.

That's exactly what I'll be doing once my system naturally drops below 7.0 as this is what my top up water will be as described in my original post.

As far as I can see, getting my top up water to 7.0 will be beneficial with my pH at the current high level and would be beneficial once my pH is low so not sure what you are getting at :dontknow:

earthbound

Hey you asked for opinions of "good idea bad idea?", that's my opinion.. :dontknow:

Wildfire

I totally 100% agree with eb, I wouldn't even worry about correcting it because in 3-6 months time you'll be fighting it in the other direction

Jackfrost

earthbound wrote:

Hey you asked for opinions of "good idea bad idea?", that's my opinion.. :dontknow:

I was thinking about any residue from the HCl affecting anything else in the system

Wildfire wrote:

I totally 100% agree with eb, I wouldn't even worry about correcting it because in 3-6 months time you'll be fighting it in the other direction

... but if it drops below 7.0 as all AP systems would do (and then some) I would actually be buffering the pH in the right direction. I think there is some confusion here. I am not trying to correct my pH but actually compensating for the high pH from my tap with the 20L or so I add every few days or so.

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