Unless you are a professional it is essential to hire a plumber, if your water pipes start giving you some problem. If you have no idea how to handle these pipes then it is imperative that you hire a plumber. They are local tradesmen that operate in every area all across that globe. They operate both individually and through a company. It is not at all difficult to find one if you know where to look. The individual plumbers are known to charge lesser fees, but they are not very reliable. So when you really need one, it is better to hire an emergency plumber from a reputable company.
Do independent research using the Yellow pages, search engines and local business listings. Beforehand, make a list of what you are seeking in a plumber on Long Island. For example, years of experience, what services they provide, whether or not they have emergency service, areas of expertise, types of jobs they perform (residential, commercial, industrial) etc. Look for local plumbing service companies that are a match.
Your third option is a regular garden hose. Bring the hose in through a door or window (have it turned off, of course), put it down the pipe as far as it will go, add towels and rags around the drain to keep water from backing up, and then get a partner to turn it on and off in short spurts. The pressure from the water might work water conditioner to loosen the clog.
If you still are not lucky in finding a good local plumber, contact your local plumbing store, they can help you in recommending a reliable and Trustworthy plumber in your area as they deal with them every day.
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.
When you are ready to commission the work, ask for the quote in writing and ensure the final bill is broken down. That way, there will be no room for inconsistencies between the two figures.