Septic System + Heavy Prolonged Rain = Burping Toilet?
Hi there, just me again to repost an old but updated question. Appreciate you humoring me ;)
I was wondering if what I'm observing is normal for an old septic system, or a new one for that matter. Here's what's going on -
I bought an old farm house that predates indoor plumbing but plumbing was installed a long time ago with a vented full bath upstairs and an unvented half bath downstairs. Everything works normal as it should 95% of the time but when we get a long heavy rainy period for several days with several inches of rain we notice that when the upstairs toilet is flushed the downstairs toilet burps. My "guess" is that the heavy rain saturates the drain field causing waste water to back up inside the septic tank, this covers up the end of the waste line inside the tank. So when the toilet upstairs is flushed this causes air to compress within the line which takes the path of least resistance to the intersecting downstairs unvented toilet line thus causing the burps.
The septic system is a terra cotta (sp?) type, we've never have a problem with it and do pump it out every 5 years. My main question - is it normal for it to back up a little as described above during these prolonged rainy periods? I can live with it as long as it doesn't back up all the way to the house but was wondering if this is typical in rain saturated soil? We do refrain from using excess water during these isolated burping times. If the downstairs toilet was vented I'd never know that this was occurring without the burp warning (the air pressure would go up the vent). Tell me I'm a worry wort, please ;)
Thanks a Bunch for any advice, be glad to give more info if it's helpful to find an answer.