I don't think it will be a serious problem but the pH will be a bit different. Depending on the pH of your water it may actually be a bit more acidic.

If it was me I'd up the processing to the quart time of 35 minutes just for an extra margin of safety but bottom line - it's your choice.

Only other option is to stop the processing, drain the jars, replace with boiling water called for and reprocess.

Dave

Thanks. I had to make a decision before I got your reply, so I ended up processing for 45 minutes, partly because of the juice vs water issue, and partly because I was afraid I had too much celery in the mix. I know that I followed the recipe of equal measure between the tomatoes and celery, but it just seemed like a lot of celery. I appreciate the help.

Another example of why these recipes need to be changed to weight measurements, in grams.