We moved into this house about three years ago. The house was built in 1970, and I expect the septic system is 40 years old as well. Last week, we started having slow drainage when we drain the tub. I went out and dug up the inspection lid to the septic tank and took a look.
The tank is rectangular. I measured it at 5 feet x 5 feet x 8 feet, so it looks like a 1500 gallon tank. There is a baffle at the output end, but no T on the output pipe. There is a V about six inches deep broken out of the top of the baffle. I'm guessing the previous owner didn't understand how the baffle is supposed to work, and took a sledge hammer to it thinking it would work better. There was about 2 inches of scum on the top, and maybe a foot of sludge in the bottom, so I don't think it needs to be pumped yet. Next time we drained the tub, we got effluent out of the top of the septic tank. That indicates the input is working fine, and I have a problem with the output pipes or the drain field. I ran a garden hose 40 feet down the output pipe, so I'm pretty sure it isn't a simple clog. I think the problem is that as we use more water during the day and less during the night, the levels in the tank went up and down enough to allow parts of the scum into the baffle area, and then let it enter the output pipe, where it ended up in the drain field pipes, clogging the drainage holes.
My boys and I grabbed a shovel and started uncovering drain pipes to see what sort of configuration we have. I couldn't find a distribution box. The output pipe is 4 inch pvc, and runs at least 40 feet. We havn't uncovered it to the end yet. There are at least 4 T's in the output pipe, which are connected to drain pipes that are 20 feet long or so. I thought at first maybe my drain field was shot, that my soil was clay bonded or something. The system is 40 years old, after all. However, then something happened that made me think otherwise.
One of my sons wasn't quite careful enough while digging for the pipe. He hit one of the drain pipes too hard with the shovel, and cracked it. It immediately bubbled up with effluent. However, it didn't bubble up more than about 8 inches. In fact, the water drained out as fast as it bubbled up. It drained until the water level of the septic tank was down to the bottom of the output pipe. That one little section of my drain field drained out more than 150 gallons of water in a few minutes. I know my soil is very sandy (I have 40 acres of sand, sand, sand!) so this doesn't surprise me very much. I think my drain field is fine.
So, I'm guessing that the little holes in the bottom of the drain pipes are clogged with solids. Probably the scum that leaked over the baffle through the break. So here's the question: How can I clean them out? Is there something that I can snake through my output pipe, that I can somehow guide through the 90 degree T's that can either flush or brush the drain pipes out? Or would it be easier to dig down to the ends of each drain pipe, take off the plug, and shove a hose or brush back up from that direction? Is this a common problem, and is there a standard procedure or technique or tool that makes it easier?