Zagz said:I would say if it appears to be in good condition go for it. I inherited 2 15 gal tanks that are 30+ years old and had to reseal one of them. I filled them up with water on the deck and let them sit for a couple of days to check for leaks. They have been running for me for a year now.
glass can become brittle ova time
Glass is actually a liquid
Glass
From Wikipedia, the free encyclopedia
Glass is a uniform amorphous solid material, usually produced when the viscous molten material cools very rapidly to below its glass transition temperature, without sufficient time for a regular crystal lattice to form. The most familiar form of glass is the silica-based material used for windows, containers and decorative objects.
In its pure form glass is a transparent, strong, hard-wearing, essentially inert, and biologically inactive material that can be formed with very smooth and impervious surfaces. Glass is, however, brittle and will break into sharp shards. These properties can be modified or changed with the addition of other compounds or heat treatment.
Common glass contains about 70-72 weight % of silicon dioxide (SiO2). The major raw material is sand (or "quartz sand") that contains almost 100% of crystalline silica in the form of quartz. Even though it is an almost pure quartz, still it may contain a little (<1%) of iron oxides that would color the glass, so this sand is usually enriched in the factory to reduce the iron oxide amount to <0.05%. Large natural single crystals of quartz are purer silcon dioxide, and they, upon crushing, are used for the high quality specialty glasses. At last, synthetic amorphous silica (practically 100% pure) is the raw material for the most expensive specialty glasses.
Glass as a liquid
One common misconception is that glass is a super-cooled liquid of practically infinite viscosity at room temperature and as such flows, though very slowly, similar to pitch. Glass is generally treated as an amorphous solid rather than a liquid, though different views can be justified since characterizing glass as either 'solid' or 'liquid' is not an entirely straightforward matter [1]. However, the notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical evidence or theoretical analysis.
A myth does exist that glass rods and tubes can bend under their own weight over time. To check it, in the 1920s, Robert John Rayleigh, son of the nobel prize winner John William Rayleigh, conducted an experiment on a 1 meter (39 in) long, 5 millimetre (~3/16 in) thick glass rod, which was supported horizontally on two pins with a 300 gram (0.66 lb) weight in the middle. Apart from the initial bending of 28 millimetre (1.1 in), the position of the weight didn't change until the end of the experiment, which lasted for 7 years. At the same time, another man, a worker of General Electric named K. D. Spenser, conducted a similar experiment independently. Two months after Rayleigh, he published his own results which also disproved the myth. Spenser suggested that the myth was composed before the 1920s, when the tubes were made by hand, and naturally some of them were curved to begin with. Over time the straight tubes were taken away, and only the curved ones remained. Some people probably thought it was the glass flowing.