We recently purchased a piece of property to build a home on and had to drill a well as there was no water to the site. As I begin to compile materials to finish out the well, I'm trying to decide what storage tank (2500+ Gal) to purchase. Ideally, I would like to utilize an underground storage system for two reasons. First, I don't really want to have the tank visible, but more importantly I don't want to deal with having hot water all summer long out here in the desert.

That being said, I'm trying to decide between utilizing a plastic underground tank or a concrete tank. My understanding is the concrete tank is basically a glorified septic tank. One manufacturer stated their concrete tanks were fine for potable water but another company stated that they don't necessarily push them as such due to (alkali?) leaching into the water. I inquired as to possibly epoxy coating the tank to remedy this but was told that customers had reported a smell of alkali even after coating the tanks but suggested I speak to a epoxy supplier about alternate coatings.

At a glance, it looks like I could be money ahead by utilizing the concrete tanks. Additionally, my gut feeling is they would probably last longer than a plastic tank but I have no experience one way or the other.

What are your guys thoughts on this? Any experts in the house that can offer some input? Appreciate it!

some thoughts.

I think you have to find out how deep you have to bury this thing to not hit the temp swings you have out there.
whatever you use, you want to minimize the expansion and contractions that might cause.

I think there are many plastics that would last a long time due to it being buried and not exposed to UV, which typically makes plastic brittle.

If concrete is that much cheaper, have you considered what they coat pools with? you would have to do the research on why they have to be refinished, but I have to believe they hold water without imparting chemicals into it.

how are you going to keep the water from stagnating or growing stuff? or is this just a pass through tank for your water supply?

What about stainless steel tanks? there are various food grade tanks that I see pop up on the market for sale and they my be a little more, but they eliminate the issues you are facing.

My great uncle died of Typhus from water from an underground cistern fed by roof rainwater.

If you have not read about Abraham Lincoln’s son Tad dying from Typhus from the White House water it is a truly heartbreaking story.

The Legionnaire’s disease outbreaks from HVAC cooling water tanks is another warning.

Do not underestimate the challenge of keeping potable water safe.

While I do not live in the Tucson area I do live in west Texas. Our "cold" water gets warm enough in the summer that you can take a shower without using any hot water and it's all underground. So you might not be getting what you want. I think an above ground tank in a well house might be something to consider. Be able to inspect the tank regularly and hey, you can AC it too, lol. Looking at a 2500 gallon tank, it appears they are about 9 foot in diameter and 7 foot tall. So not even a big building is needed.

I lived at a place years ago that had a private water system that supplied a number of homes. The property owners wanted the water supply equipment out of sight. They built an underground storage room. If I recall correctly, the walls, floor and ceiling were made out of concrete. In this room they placed a large pressure tank. Seems like it was like a 2,000 gallon, metal pressure tank. They also had a water pump in there along with a few other things.

I was only in there one time. Access was via a ladder. I have no idea how they would have removed the tank if that ever became necessary.


A friend lived at another place years back. He had a rather small spring for a water source. It may have flowed a half a gallon per minute. The spring did NOT supply enough water for periods of heavy water demand. My friend had a pump at the spring that pumped the water to a storage tank. I don't recall the size of the storage tank. Seems like it was only a few hundred gallons. He had a plumber design the system and was quite happy with it.

There area few ideas. Perhaps one of them will be helpful.

They make plastic tanks for the specific application you are looking for.

Underground Water Storage Tank

Underground Water Storage Tank Alternative

I am sure there are other vendors out there.

My house is on the underground municipal water supply in Las Vegas. When I shower in the summer, I take "cold" showers as the water is plenty warm already. I don't know what your temperature differential would be between above ground and underground water storage, but it may be worth checking out before spending a lot of money to bury the tank.

Mine looks like the first one pictured but is 2000 gallons. We packed sand around it as we burried it to keep rocks from puncturing it, we also filled it with water as we burried it to keep it equal-ish pressure on the inside and out till it was totally in place, it works great. Water slowly pumps in one end and is pumped out the other end into the house as needed witch allows sand to settle in one end of the tank, we run it low once a year to suck out the sand with a wet dry vacuum cleaner even though there is not too much sand, we could probably let it go 5 years and be just fine.

If you have a really low volume well get a little bigger tank with an irrigation pump that's not running off your electrical panel in the house so you can fight a fire if needed.

Basically you are describing a cistern. They have been around a while, the Romans used them. Down here they are required by code, our roof drains into our cistern, you need at a minimum 10 gallons per square foot of roof. Our cistern is about 9000 gallons. It is poured concrete under one end of the shop and the walls are part of the foundation. The coating we use is Thoroseal, you mix it up with water using a powerful drill and a paddle wheel. Brush it on with a broom, do a couple of coats. Our contractor said when it starts filling up use some pool salt and brush it all over the surface, then pump out. This gets rid of a sheen it tends to leave. There are some tricks to the downspout system to keep a lot of dirt out, that goes a long way to keep the cistern clean. Our filters consist of a back-flushable filter with a mesh screen, we purchased the finest mesh they sold. Then a 20 micron paper cartridge filter, after that a 5 micron carbon cartridge filter. The carbon takes out any hydrocarbons or chlorine in case we dose the cistern (rarely) with bleach. Been drinking out of it since end of 2012, before that our old rental had a similar, actually less filtered setup. Still kicking.

If you want to take it to the next level install a UV filter AFTER the other filters. The reason to install it after the particulate filters is the UV light needs to hit the nasty critters, particulates in the water can block that. Check out ultraviolet.com, they make some nice stuff, we put one in a 55 power cat I designed so they could use tank water rather than the stupidity of bottle water. Works great.

Abraham Lincoln's son did not have access to a UV filter, he would be fine now, as long as he got his vaccine. Grover Cleveland's son died at I think 16 from an infection from a blister he got playing tennis, medicine and the ability to have clean water has come a long way. Unless of course the refinery on the South shore they are trying to restart on the cheap has massive flares and dumps raw crude oil drops on your roof and garden..... That would probably overtax the charcoal filter.