If you need immediate service from a plumbing company, you should find one that happily offers it to their customers. Some even specialize in providing fast repairs and replacements. If you think you need this kind of immediate help, you should learn what to look for in a local business.
Choose a good contractor with both plumbing and construction skills who can work around tough problems because not all plumbing jobs go smoothly. Ask the contractor to see if he has met all of the city codes before in the past for your region.
Some faucet repair valves do not take washers and therefore you cannot repair them. If you have a washerless shut-off valve that leaks it will need to be replaced. You will need: a propane torch, solder, flux, sandcloth, a wire fitting brush, a small section of copper pipe (most likely 3/4" I.D.), a slip coupling (again probably 3/4") and a shut-off valve. I would highly recommend installing a ball valve with a drain on it as opposed to a washer style valve. If you purchase a decent quality ball valve it will last a very long time.
For this reason it is highly important to make sure you are prepared in a plumbing emergency. The first thing to do then is to make sure that you already have the number of a plumber in your phone book that you can find immediately. The sooner the emergency Trustworthy plumber gets there, the less damage you'll do and the less water you'll waste. Meanwhile you will be more likely to be successful in having your plumbing repaired. Don't make yourself rummage around to try and find the number of a plumber at the last minute - keep it somewhere where you can retrieve it easily when necessary.
Third, if you dissemble things, do you know how to put it back and not cause further damage? This is something that commonly happens. Some people attempt to fix the problem and end up causing a lot more damage! Then they try to do something else, which causes even more problems and by the time they call the Local plumber, the problem is much worse and now, they not only have to pay for the service but may even to pay a higher amount for the double repair.
As precautionary measure, you have to tell all your tenants where their individual water shut off valve is located, as well as the entire building's so they can turn it off in case of emergency. And don't forget to make them accessible. It won't do any good if they know where it is but it's locked and they can't break in.
Once you have become a master plumber you can start your own plumbing company or you can even work for the government. This may sound like it is going to take forever to become a master plumber and it is difficult to achieve this level but it is not. Yes, it is going to take several years but the prestige title at the end is worth it.