How large of a storage tank is necessary?

So the property that I recently purchased has a low flow well that was filling two storage tanks, about 2500 gallons each that were then gravity fed to the two houses. The upper tank, after much work, was discovered to be cracked, but the lower tank is fine. I've opted to bypass the upper tank for now, and just function with the lower tank. The well company seems to think that I will need more water than that, and I'm not sure why. Am I missing something? And they seem to be encouraging us to run everything without the storage tanks, but if we had been doing this previously we would have had nothing to fall back on when the pump failed.

Hmm, I'd think the wife and I could get by on 2500 gallons for about 100 days.  Unless it's needed for irrigation as well?  I'd just live with one tank but I'm not a tank expert.  As long as it's safe to have water sitting there that long?

Does the tank constantly refill via the well?
We have a 50,000 gallon tank, which is only filled by rain water. It works fine through winter, as it refills regularly, but in the spring and summer, it has been raining less.

I would guess my family of 3 would go through 50,000 gallons in about 45 days from full, with no rain - this doesn’t include our drinking water. Our biggest water expense is the washer. Even with a “super-efficient”, new machine, it uses a ton of water!

We collect drainage off the other roofs for a small bit of irrigation, and backup water, but this year i’ve tapped into a small, muddy groundwaterspring of sorts which i can use for the gardens.

I have a well that has a low flow, or more properly a low recharge rate, towards the end of summer and thru the fall.  It is realy good to have a storage tank for one of these ! When we moved in, there was no storage tank and we would drain the well and the pump would shut off when we were watering the yard.  SO, I learned to not water the whole thing at once, and we sometimes had to go and reset the pump to restart it after waiting for a bit.  

It is more convenient and better for emergencies to have reliable access to more water at once, eventually I bought a water storage tank.  Due to money issues at the time, I ended up getting a 2500gallon storage tank.  It has been wonderful, this storage is a great buffer so that we can take a shower and water the yard, and the whole yard even at once.  Not to mention water for any power outages, other emergencies or for fire danger, of course we might wish we had more for fire suppression, but this 2500gallons is a whole lot better than before.

I cannot imagine why anyone is advising you to bypass a storage tank.  

After a well pump replacement years ago, it turned out that the much-advertised dry pumping protection did not work as I thought it might and during the dry times of year, the well was often pumping when the well had not recharged sufficiently and there would be a small trickle of water going into the tank, this used ALOT of power !  ( What you want is for the pump to turn off and try later...) I dont know if this is what they are afraid of with an empty tank wanting to be filled, that your pump will run and run with dribbles coming out, which costs alot of money and wears out pumps  ?   The way I solved this was to get a 24hour timer that I hard wired for the pumps elcctricity input, it is a very simple timer with a circle of 24 hours and a liitle dip switch at every 15 minute interval.  I just decided to try setting it to one 15 minute interval once every hour.  For my well, this was sufficient, could be that I could keep it on more, but I dont need it on more.  This gives 45 minutes of recharge time for every 15 minutes of pumping time.  I have never had an issue since I did this.  ANd, I never have no water as 2500gallons in the tank is alot of water.  

Debi - I think you are understanding my predicament exactly. We are also off-grid solar, so our well pump turns on between noon and three each day, which allows for the well to replenish and the power to be there, but when something fails, it's problematic.

Stacy Witscher wrote:Debi - I think you are understanding my predicament exactly. We are also off-grid solar, so our well pump turns on between noon and three each day, which allows for the well to replenish and the power to be there, but when something fails, it's problematic.

I am solar, but grid tied ( with battery back up too, old school, solar for 20 years now).  Because I am still grid tied and use the grid to buffer some of our electric use, and they pay different on time of day, I have my well pump off all day and only on for  15 minutes out of every hour for "off-peak" night hours, about 8 hours a night.  This is also better for the area as a whole that my afternoon solar-power powers neighbors and I pump out of the well with excess grid power at night.

Because I want to be able to run my well pump off the batteries/inverter when I need to, or want to, I have a lower power pump than many of my neighbors, so they have something like a 1hp 240V pump and I have a 120Vpump that is -- I forget -- 1/2hp or 1/3hp.  People are running a larger pump than they need to.  

(  I would like to be able to be grid independent if I need to or wanted to, but right now I would not have hot water as conveniently as I would like if I did so.  I am also one of the few houses here that has no propane, so I dont see a need or desire to add in a propane delivery, and my electric water heater and electric stove would be too much for my solar system to power.  So, even though I make enough electric, it is not pwerful enough for those 2 appliances, so I cannot tell PG and E where to put it..... in PG and E power outages, we are great,  except all hot water and cooking is off the woodstove then.  I have fantasies of someday having a biogas set up and having gas for hot water or cooking )

-- Oh !  I just made the connection that you were on the solar battery thread -- I am the person who has Aquion batteries for 3 years now.  

It is too late for you right now, but when this well pump goes out, hopefully not soon, many years ! , but when it does I am just going to get a DC well pump and give it its own solar panel ( or 2) over by the pump huse, because that is all that is needed, a nice, slow DC pump , no batteries, just charge controller and the pump can run when the sun is out and that will be enough.   Just putting that out there, food for thought, simple, not needing to have anything to do with house system

We don't have well water but 2500 would last us two around 17 days, it would be more in the winter and less in summer due to watering, so whether you want the other tank back depends on how long you want backup water.

Our first (windmill pumped) gravity use tank was an old reclaimed redwood 'leaking lena' of about 1200 gallons. We used it for house and limited garden watering until we added a second 2500 gallon tank next to it. Having 2 tanks allowed us to expand our garden/yard watering as well as create a early warning - low water! - method. Our low volume well was never over taxed by a low volume pump (first windmill, next solar) that stored water for  use.

How much use you demand is the bottom line. Developing ways to use LESS water is more economical and cost effective than buying a larger or additional tank. Ever think about the clean water that you run at a sink to waiting for hot water to come? or running while washing hands/brushing teeth/scrubbing vegetables etc.? Once that clean water hits the sink its only fit for the septic tank! We have a 3+gallon bucket in our shower that we collect the cold water into until the hot arrives at the shower head. The cold water is then used for other uses (garden/flushing toilet). Likewise we have 2 gallon containers under our kitchen sink for cold water that would otherwise go down the drain. The water in the jugs get used for cooking, plants, dog's water bowl, filing tea kettle etc.

The best ideas are not how to have more, but need and use less.

We don't use that much water. I think that the 2500 gallon tank will be sufficient for us. I just wanted to double check because the company doing the work seemed surprised by this. I only want to use the well for water for the houses. I want to increase our rain water collection for more irrigation. I think that is a better idea.

One of the pluses for repairing the upper tank at some point is that the pressure to the upper house would be better from the upper tank, right now, we are repairing a pressure tank under the upper house to increase pressure.

There is also another well on the property that isn't fully developed, the previous owners were going to develop it with a stand alone solar pump, but they sold the place first. So we could in the future do that for more water.

Thanks to everyone for the help.

I store about 200,000L
Because we have low rainfall.
And we do not waste it.
The volume you need will be a function of what you use per day, and the volume of water reliably  available per day.
You storage volume has to cover enough to get you through a long dry spell.

Why not top up with rainfall at times its available?

To better help, how much water do you use on average per week or per day?


Inside your house, you probably use less than 250gallon per day.
You already have 10days+ worth of water stored in the tank. Why do you need more.

Assuming you are using 240gallons per day.
I think your well can produce 60gallon of water per hour (times 4hours).

A water bank and a battery bank of 3days is more than enough "storage" for the days when there isn't enough sunlight. So I find 2500gallons of water excessive.

Alot of folks only have a 60gallon pressure tank.


Now if you want to have enough water in case your pump/well fails and someone has to come out and fix it. Then yes 10days supply of water sounds good. Because in an emergency situation you could make it last a month.

But it is entirely possible that you water acres of land.