Some of our local Home Inspectors will also flush some phosphorescent dye down the toilet to see if it will evidence itself out in the yard, temporarily glowing faintly over the Leach Field (which it isn't supposed to do); sort of like a mini nuclear waste dump . . . . but just for a few hours.
That technique doesn't work so well during the winter when there's several feet of snow on the ground; but I've seen it appear when there's just a couple inches. Makes the back yard look kinda tasty . . . . like a giant lime green slurppie; but you probably wouldn't want to sample it, regardless of how attractive it might appear.
Around here, you're much more likely to have a failed leach field than a problem with the concrete or fibreglas septic tank. The mean water table may have been fine at the time of installation, but drainage patterns will often change and the water table may rise in a wetter than average year . . . . plus people from the city tend to put all kinds of junk down the drain that will clog things up and/or kill the beneficial bacteria . . . . like garbage disposals used to excess (which are really incompatible with septic systems anyway), Draino; bacon fat, Pampers, bleach, sanitary napkins, more Draino, cooking oil, ammonia, motor oil, condoms, and then more Draino. They need to go back to the City; where municipal sewage treatment facilities are prepared to deal with almost anything ?
Dale C. Hittle of GOLDEN RULE PROPERTIES in Glover, Vermont
Where We're Always Striving To Put Together "THE FAIR DEAL"