how much ph down to use?

Hi everyone, first I know the correct answer to my question is 'get a ph meter and use it.' I have two and both are busted, have another on order but it won't be here for 1-2 weeks. In the meantime, I have a 3 gallon DWC bubble bucket going with 2 G-13 labs poison dwarfs about 5-6 weeks into flower that I'm growing for seeds. My tapwater usually has a ph of about 7.1 and I want to bring it down to 5.2-5.4. Can someone give me a 'general rule of thumb' as to how much ph down per gallon is needed to adjust my ph to what I'm looking for? I know it will vary depending on water hardness, etc, I'm just looking for a stopgap until my ph meter shows up. I'm using GenHydro nutes doing the Lucas method (micro and bloom only at a 1:2 ratio, shooting for a tds of about 1100ppm-- yes, I do at least have a working tds meter). I swear once my ph meter gets here I will use it like it's the word of god itself. Any help in the meantime is greatly appreciated!

nobody can help you with this...it is completely inaccurate to give a "general rule of thumb" when using PH down due to the variances in water/nutrients/ph down/etc...get a new meter

It might not be the best advise but I woud say use nothing until ya ph reader arrives, as in no ph down. 7.1 ph (ya nutes will prob bring down a bit also) aint gonna do as much harm as ph 2 coz ya put to much in. PH up'n down are very powerfull chemicals and only a few drops can make a big difference. Your call matey.

As said, no general rule of thumb, even where you get your water from could effect the thing.

For me, my water comes out of the tap at 8.something. If i have 25L in a tote, after adding nutes i'd typically add say 5ml of down. If in a 5L watering can, typically say 12 drops. But that could do anything and everything to your plants.

IF it's going to be 2 weeks to arrive, cancel your order an buy elsewhere so you have it in a couple of days. even just drive down to a pet store and pick one up. I would happily just give the plants water at ph 7 for a few days, but i would not be uing ph down for 2 weeks without a means to test what i'm actually giving it. I've killed a plant before in that manner.

your aNSWER BEEN ANSWERED ABOVE, ILL LEAVE IT

alright thanks all, it was worth a try.

Sweet, I was sitting here moping over my ph, then remembered I thought I'd come across an old PH meter in the garage. Dug around and found a serious piece of science lab equipment: a Corning PH meter 125. It's nice to have parents that are both chemical engineers AND hoarders. Found a probe for it, got it calibrated with some PH solutions I had laying around and am in business. Wound up putting about 5.5ml into my 3 gallon hydro bucket, then 3.5ml into my 2 gallon mini-DWC setup with seedlings in it. Saved~!