PH rising in small 4 gallon rez

Ok 4th grow and I set ph to 5.0 and it rises to 6.5 and then I set it again to 5.5 and rises to 6.2-6.4 range... My water out of the faucet is about 175ppm. My question is if I filter the water before I put in my rez will that make the ph more steady ???? Cause what is making it rise the chlorine ??

nah... chlorine that is commercially used is more of an acid than a base.


I am no expert on why your pH is changing but first thing that comes to mind is that evaporation is changing the contents of you water... but im sure your res is covered so that probably negates my assumption.. hmmm

theres gotta be a better way than filtering all your water bc that will be a bitch.. is your pH meter on point?

Are there nutes involved?

Ph rise is a normal thing. Between evaporation and the plants usage you will see flucuations in the ph. Filtering your water or using R/O will not make difference. 175 for your tap water is not a bad thing, just let it sit for 24 hrs. with an airstone. Won't help with your ph issue though.


you don't say what medium you are in? In hydro a swing of 5.5-6.3 is O.K. and for soil a swing of 6.3-7.5. Start your res at the lowest point and watch it until it reaches the highest point then either adjust or replace your res.

Good Luck

when i use tap water had a lot of problems wiith ph want to rain water and it stopped also small res heat up quickly and that alone will raise the ph imo get a bigger res firstlike 15 to 20 gal that will take care of heat and evoporation problems in ph if still a problem different water source

superstoner1 said:

Are there nutes involved?

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Nutes are general hydroponics and I let water sit out for about 20 hours with no airstone.... Medium is the gro-dan A-OK starter plugs... Wish I could just set my ph and forget it..


Also before I forget can you have too much water movement in rez cause of airstones ???

no the more air the better whats water temp that will make ph raise and so does tap water from towns and advaced nuts make a ph perfect nuts that they claim never tryed it though

Do you have the cubes in hydroton?

That would be the first thing I'd eliminate if you do.

Taviddude said:

Do you have the cubes in hydroton?

That would be the first thing I'd eliminate if you do.

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What do you start your clones in if you're not using cubes?

RenMasters said:

What do you start your clones in if you're not using cubes?

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I just use neoprene inserts. Works like a charm! Then I put the rooted clones into net pots and fill with hydroton!

If your PH is rising that quickly, what is the PPM's of your solution? Sounds like you are underfeeding.

I run on a weekly cycle and use the ph level of my res as a guide to when to add water. I start out at around 6 (flower) in a 135L res. As the week progresses I can watch my PH start to slowly drop. When it reaches 5.8 (typically day 4). I refill with 20L of well water and a small addition of nutes and that will raise it to 6 again. I may be way wrong here but I assumed that the PH was falling due to higher concentrations of nutes in res. If I underfeed the PH will rise slowly as well.

If that is the case you should reduce your starting nute ppm. The key is to find the sweet spot where nutes and water are taken evenly over time. I rarely have to do any ph adjusting after the first day of a new res. And also keep in mind the plants like slightly different ph levels depending on what stage they are in, mine never see 6 until week 5 of flowering.

superstoner1 said:

If that is the case you should reduce your starting nute ppm. The key is to find the sweet spot where nutes and water are taken evenly over time. I rarely have to do any ph adjusting after the first day of a new res. And also keep in mind the plants like slightly different ph levels depending on what stage they are in, mine never see 6 until week 5 of flowering.

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Thanks but I have got it as close as I can I think lol. Perhaps my water is different, if I reduce the amount of nutes my PH goes up as week progresses. And plants are happy I think lol.