Purigen

[Apistomaster]

Purigen do a great job as cleaner aswell but after recharged it produces ph swings if you your tank water is acid treated, if you leave it without last acid step during recharging it raises ph so much and if you do the last treated acid step then it low ph below the value and even to dangerous value very close to ph 5.0, this has been fully tested by me, of course that's no problem if used on ordinary tap water in that case that apistomaster says it is very useful as cleaner.

The directions on the containers of Purigen I buy only instruct soaking the used Purigen in a bleach solution then dechlorinate with Prime. Nothing is said about an acid wash.
I have not detected a change in aquarium water pH in conjunction with Purigen use.

I often just rinse it until I can't detect any chlorine smell and skip the dechlor stage altogether.

[Polar_Bear]

I agree with Larry. While I no longer use Purigen, it's just too much of a PITA being so small, I also never had pH swings with it. I also only rinsed it well and used a de-chlor, no acid wash.

[guille2007]

The directions on the containers of Purigen I buy only instruct soaking the used Purigen in a bleach solution then dechlorinate with Prime. Nothing is said about an acid wash.
I have not detected a change in aquarium water pH in conjunction with Purigen use.

I often just rinse it until I can't detect any chlorine smell and skip the dechlor stage altogether.

Under conditions you say it raises ph very high cause by bleach residual that leaves it very alcaline, read Seachen instructions, they recommend acid buffer to try to create a ph balance but that does not work in sensitive acid water like the ones that could be below ph 6.0 it has been tested by me several times so there is not doubt for me about tht, of course it happens just after recharging and at the end it will get stable but just after several days of producing ph swings. If you use in just dechlorinated tap water you won't notice anything since that is already alcaline water. Try it in water with ph below 6.0 and read it after 12 hours of adding recharged purigen.

[guille2007]

And here you are the origin of the problem, all this from Seachem:

Regeneration: Soak in a 1:1 bleach:water solution for 24 hours in a non-metalic container in a well ventilated area and away from children. Rinse well, then soak for 8 hours with a solution containing 2 tablespoons of ChlorGuard™, Prime™, or equivalent dechlorinator per cup of water. Rinse well. For freshwater use, soak for 4 hours with a solution containing 1 tablespoon of buffer per cup of water (Discus Buffer™, Neutral Regulator™, or Acid Buffer™). Original color and full activity should now be restored and Purigen™ is ready for reuse. Caution: some slime coat products may permanently foul Purigen™ and render regeneration difficult. Do not reuse if odor of chlorine is detectable. In case of doubt, soak beads in small quantity of water and test for residual chlorine with a chlorine test kit.

And also this Q and A from Seachen:

Q: I recently just regenerated the Purigen product. In the end, I used your neutral buffering product for the final process rather than the Discus or acid bufferer like suggested. It was under my rational that the reason we use the buffer was that the regeneratory process basically renders the product as at one extreme end of the PH scale. We are basically just preventing it from affecting our overall PH by buffering it. Since I strive to keep my aquarium at a PH of 7.0 was this a correct action on my behalf ?

A: This was a correct assumption and I do not see a problem with your action. As a precaution, I would test it in a cup of water (preferably RO or DI). If putting the fully regenerated product in DI water results in the pH of the DI water rising above 8.0, I would reintroduce the resin to a solution of Neutral Regulator for a few hours