Not to be a stickler, but I'd be careful with Tap Water. What comes out of the tap varies greatly throughout the world. In many locations the tap water is very hard with high levels of mineral salts. Generally not the best to use on the soft coatings of filters.
This is not a problem for me in the SF Bay Area because we get very pure, soft water siphoned from the Yosemite Valley. It WAS definitely a problem when I lived in the Las Vegas Valley and the California Central Valley. That was nearly 20 years ago, but the hard water in those areas left more residue than it removed! In recent times, I have been at locations in the Southwest and the Midwest and I can attest to the fact that in many of those locations the water has high mineral salt contents.
Now, for English water, I have to segue to my beer brewing. I dump a "Hell of a lot" of mineral salts to replicate English tap waters to make British ales.
The mineral concoction is commonly called "Burton Water salts".
I do agree with Ralph that sometimes a dish detergent will help, especially where there are organic and/or oily residues.