Ph 5.0 24 hours after pitching, 1st time with a ph meter

OK, so I'm a little worried; I have no visible signs of fermentation yet 24 hours after pitching a starter of wlp800 pilsner lager yeast. I had a wort ph 5.4 before pitching; it is now 5.0. Is this OK?

This also only my second lager ever. The first one I used s-23 and it started fermentation sooner than this.

I'm asking this because I have a couple of packets of s-23 waiting in the wings; just wondering if and when I should re-pitch.

Thanks

Relax, sometimes a bit of time can pass before you see signs of fermentation, but the fact that the pH dropped is a sign that it is. Cold wort absorbs CO2 so the tell tale signs of bubbling are repressed.

First time I have heard of anyone messing with the wort that way that soon after pitching by taking a ph reading.

This is a good sign. It means that even though you can't see anything yet the yeast are busily establishing a favorable environment for themselves i.e. one where the pH is too low for competing organisms. Try looking at the surface of the wort from a very low eye angle while illuminating it with a flashlight also from a low angle. You may see scintillation at the surface from tiny priprick bubbles breaking it. I expect you'll see gas evolution pretty soon.

This is definitely one (of several) reasons for owning a pH meter though few seem to realize that it can be used to great advantage in this application.