One of the first things we did before moving back into our house was cleaning the gutters and the cistern so that we had a clean water source. I hate the thought of wasting water, so we pressure washed for days, did loads of laundry, and washed anything we could think of before the cistern cleaning day. This used up the majority of the water that was in the cistern.
Now, how to clean out a cistern?? Aaron and I both grew up on farms and very often had to clean out water troughs for the animals, so the process is really pretty much the same as that.
First, have clean water ready to rinse and clean the walls. We had about 70 gallons of fresh clean water ready for use. Next, get a sump pump, long water hoses, brooms and/or brushes, buckets, dust pans, and flash lights. Next, get in the cistern and start pumping out the water and scrubbing.
Our cistern access is under our sink which is a really tight fit. I mean really tight fit! I almost had to get in instead of Aaron but luckily he was able to squeeze in. We actually had to quickly build a skinny ladder to use before we could even start. Maybe just a bit behind schedule... Imagine a ladder, multiple electric cords and water hoses already in a very tight opening and then you have to also squeeze in past plumbing to the damp darkness below. Fun right? :)
Once Aaron was inside, he started pumping the water out and washing the walls. I didn't really do much at this point except try and keep Penelope happy and offer some kind words to Aaron who was not really having that much fun. Super humid and dark down there... Once the sump pump couldn't really get any more water out, we pumped some fresh water in for a rinse, scrubbed the walls again, and then pumped this water out. Then, we repeated until we were happy with the cleanliness. Penelope was really pissed off once we began the first rinse so we were trying to hurry and not get snappy with one another. Since we were staying at a friends house, we were trying to wrap up and get to where we could shower, eat, and go to bed. It was already 9:30pm. Way past the baby's bedtime! No project is enjoyable with a baby screaming...
Thankfully, we were done by about 10 pm and were happy with the results. Water delivery came in the morning and it rained that night which put us at about 1/3 full. The water level is VERY important to all of us who live on an island and rely on the rain for our water, so we watched our cistern for weeks. Thankfully, we are now at 3/4 full and all is well :) Hopefully we don't have to do this again for a long time!