Cistern Re-seal Job in STT

The cistern has to be drained - losing all your stored water but hopefully with renting a truck in your driveway, and the requisite plumbing adjustments to save enough water for the duration of the repairs - then all the 'muck' has to be shoveled, carried out - through your living room or wherever the cistern lid is located - the walls get washed and that water pumped out - then fans are put into the cistern to dry the walls - this is the time to patch any leaks - then the walls are coated - dried and commonly re-coated - that final coat is washed down and vacuumed out - dried - and ready for new rain.
Generally about 10-20 days - really depends on the level of repair work needed - if you have them slope the floor so it can self clean with an added new drain pipe at the bottom - useful when the cistern is overflowing and you are not wasting water - you can add years to the need for any cleaning process.
It is a messy, disruptive job, with many people in your house for many days - get a bonded company - Be there all day and if you have to pay someone instead to be in your house supervising the crew it is worth it. Make sure they use heavy plasic everywhere inside and take all the 'muck' away.
Call more than one company and get some bids. Read the contract, have a lawyer read the contact, inspect the work daily - It will be in the thousands, not the hundreds.
If it is not leaking I personally would not understand the need to recoat it. IMHO.

If you are indeed dealing with a leaking cistern you might also look into cistern liners. A few years back I knew someone here who used to order them custom-made from a stateside supplier and then install them. Do a google for cistern liners and you'll find a ton of suppliers - you can even install one yourself if you're handy! As far as the actual cleaning is concerned it may not necessarily be a really messy or time-consuming job. Some contractors nowadays will use a commercial vacuum (like a super heavy duty wet/dry vac) to eliminate the manual removal of dirt through your house. They snake in a big flexible hose through either the cistern overflow outlet or directly via the cistern cover and just suck it all out into a disposal tank.

Many houses have at least two cisterns, so you could just move the water to another cistern instead of renting a tank truck.

You may want to prevent new rainwater from getting into the empty cistern.

When working in a cistern, have somebody watch you from above, in case you get into trouble. A friend of mine was stuck in one for a day when he went in alone and his ladder broke.

Cisterns can potentially be filled with dangerous gas. You may want to ventilate the cistern with forced air before and during the work.

Big Lee. That what he does. He's in the phone book.

I have used Albert Brin in the past and he did an excellent job in about 7 days. PM me for his number if in STT.
Cistern shall need to be completely drained, cleaned, resealed, then there is a curing process that takes a couple of days before you can put water back in.
If you must stay on your property, rent or purchase one of those heavy duty 600 gallon water storage containers from Home Depot or other sources. This can be connected to your water pump. You can then store your water there to use if you must stay on property. If you have a good neighbor and a long hose, give them your excess water. Ideally, it is best to stay some place else while the cistern is being cleaned and resealed unless you have access to water.

Good Luck.

Anybody that doesn' install a cistern liner is asking to constantly drain/clean & re-seal cistern every 3-4 years. Too many tremors from earthquakes that most of the time nobody realize have happened, causes small cracks in cistern wall and therefore you end up with a "leaky" cistern.

We used a product from DLM Plastics and never had another leak.

http://dlmplastics.com/product/rainwater-harvesting/cistern-liners/

Jumbie - STX - Now living in Ohio

Thanks for all the valuable advises. It shows there is a ton of knowledge on this board. You guys are the best.

The house has two cisterns, so we can do them one after the other. There is no apparent water leakage from the cisterns, but we noticed that one wall against the cistern felt a little damp. Also the house inspector suggested we have the cisterns re-sealed. I don't know if the cisterns are lined or not. Will check the internet and discuss with the contractor to understand the situation.