Unfiltered tap water for wort top-off, sulphur smell

[Shiggity]

I had forgotten to buy distilled water up to the point where it was time to top-off the wort, so I decided to try tap water. It's been 48 hours fermenting with Saflager S23 at about 67 degrees ambient room temp, 70 degrees carboy temp (it's in the coldest part of the basement) and the water in the bucket that the blowoff tube is sitting in smells like sulphur, enough to make the sulphur smell evident from even several feet away. The fermentation is very active and I was wondering whether this is a normal variant of the yeast or whether the tap water, which comes from a natural aquifer and is tested by the water district regularly but unchlorinated, could have had high enough of a bacterial load to outpace the yeast.

Edit: I tried adding a penny to the blowoff water and it seems to have neutralized it

 

[microbusbrewery]

Yeast will do that, some strains more than others. That said, I'd be a little concerned about untreated tap water but I tend to be very cautious when it comes to sanitation. Even though it may be sanitary at the source, you could have bacteria at the spout. If it were me, I'd pre-boil then cool your top-off water.

 

[GHBWNY]

Sulphur will usually go away with time. Get it all the time with my hefes (WLP380) and it always goes away.

 

[Shiggity]

Just to follow up, the batch went great. No trace of sulphur smell or taste in the conditioned bottles. Also I made a mistake: the yeast strain was Saflager W-34/70. Sorry about that.