Fermentation yeast question

brewed a British bitter extract kit. Followed instructions on dry yeast pack to activate in 4OZ warm water. Only got vigorous fermentation with yeast for less than 18 hours then nothing. Had a longer/stronger activity when a pitched dry yeast into fer mentor. This happened also when I brewed a irish red extract kit which is now in bottle. Should I be concerned or do anything at this point to bitter in fermentor? go back to pitching dry? or use only liquid yeast from here on out? Tanks

rehydrating vs. not rehydrating is a debate that has yet to die among homebrewers. I’ve had great results with both, and have not been able to perceive notable flavor differences.

Bubbles from the airlock do not equal fermentation activity. Could be that it was a different yeast strain, wort temperature, or likely a combination of those and other things (please tell us those things, as well as gravity of the beer). While bubbles, krausen, and odors are SIGNS of fermentation, the only way to tell is to take the gravity of the beer.

If this is a normal gravity bitter and you pitched a sachet of S-04 or something, this contains plenty of yeast and it will ferment.

Did you rehydrate in spring water at about 80°F? RO water, distilled water, and treated water will damage the yeast.

Why is that?

Why is that?[/quote]
The osmotic pressure created by use of the three water types will cause cell wall ruptures.