Hi, i have just bought my air tank from someone.
1st question: does a tank need to be tested every few years?
2nd quesrtion: if so, where would i take it?
Yes, it needs periodic testing - either every 3 years or every 5 years depending on what standard it conforms to. There is a manufacture date in the form MM/YY on every tank (sometimes the month and year are placed either side of a manufacturer's logo) which would allow you to calculate when it is due for retesting. When a tank is successfully retested, the tester will fix a label with the test date on it; the tank can be retested several times up to its maximum service life of 15 years.
The place most of us get our tanks tested is H-PAC (http://www.hpac.co.uk/) who will be able to provide authoritative information concerning your tank.