Why does water rush through pipes when no water is being used?

Question

We live in a house with city water, septic well, water softener and sump pump. We periodically hear a very loud sound of rushing water through pipes in the house. It lasts about 15 - 20 minutes. This happens every few weeks.

What on earth causes this? We live on 2 acres, there is only the two of us living here. We can hear the sound loudly in the laundry room (probably due to drain area for washer) and it sounds like it is coming down from the attic. We have one furnace in the attic, but it is not always on when this happens. We can also hear it loudly in the exposed pipes in the basement.

Any ideas?

Answer 1

This sounds like the backwash on your water softener.

It should be set to cycle at 1 am or so when you wouldn't hear it, but the clock could have been reset from a power outage. Normally, it will trickle for 20-30 minutes as it brines the resin bed and then it will backwash the resin bed with clean water for 10 mins or so. This water must all be dumped to a drain somewhere, possibly in the laundry standpipe. That's where mine dumps to.

Check your softener settings,and look for a correlation.

Good luck!