Carbonator cap for making seltzer

I'm trying to use carbonator caps to carbonate 2l bottles of water for seltzer and am having trouble with the carbonation level - it always seems very undercarbed compared to store-bought seltzer.

I leave the water in the fridge overnight to get good and cold. I set the reg to 35psi, purge the air from the bottle and hit it with CO2. Shake shake shake, hit with more CO2, repeat until the bottle stays rock hard after a good shaking. It still seems undercarbed.

Do I need to leave it on the gas? Or leave it overnight? I'd rather not leave it on the gas as the cap doesn't seem to seal very well.

Thanks,

-Joe

Joe
I found that it takes more like 50psi and shake, then let it sit for a day, bring it back up to 50 psi, shake, repeat, and in a day or two it's right. Soda is WAY more bubbly than beer, and as the soda absorbs the head pressure, of course the pressure drops and you need to refill it. The old seltzer bottles used a full co2 cartridge and made fizzy water but not as much as we're used to with commercial soda/seltzer water.

Thanks. My regulator won't get to 50, unfortunately. I get 40, tops, which is the highest pressure the carbonator cap says you should use anyway.

I'll try refrigerating it overnight and hitting it with more gas and see how that goes.

-Joe

i'm assuming you're using the commercially-available, blue plastic carbonator caps made by liquid bread?

they generally don't leak unless the top sealing edge of your bottle is nicked or damaged in some other way. most likely what's happening is that after you pressurize and shake until the bottle is hard, you put it back into the refrigerator for a rest and during that time, the co2 is absorbed by the water and the bottle goes soft again....

i leave bottles with carbonator caps on the gas 24/7 at 30psi, no problem. plain water carbonates overnight, soda takes about 18-24 hours due to the dissolved sugar.

Is it leaking only when the gas quick disconnect (grey) is on. I bought one that did this, the vendor sent me another one and it did the same thing. I tried different quick disconnects and finally found one that didnt leak. Its weird because the disconnects work fine on my corny post, but I suspect the carbonator caps are a bit smaller than actual posts.

I would suggest shaking it while the gas is connected and possibly also leaving it on the gas over night. The colder the better.

It helps if you leave a couple inches of head space in the bottle, makes for faster mixing. I do this, then squeeze the bottle to remove all of the air before tightening the cap. Shake until the regulator stops making noise. Only takes 4-5 minutes.