Why are storage tanks always before water treatment?

[Blamus]

Hi, I'm new to well systems and I just had one drilled for a new house. I've lots of questions because I'm very curious as to how the system is designed and why etc. (my background is in chemical engineering). However, my first question is, in general, wouldn't the storage tank positioned after the water treatment make a lot more sense? This way, you're storing clean water. In power outage, or water treatment equipment failure you have a giant tank of clean water to use. Even if the well runs dry (fingers crossed), you can call and have water hauled in and use the same storage tank for clean water from a water truck. In fact, there are a few neighbors here simply dont have wells, they have a water contract and a big cistern.

So why don't people design the storage tank for the clean water rather than the pre-treated water?

we have very hard water here. smells of sulfur etc.

 

[Reach4]

One advantage of an atmospheric tank is that sediment settles and H2S can go away. You do have to remove sediment after a while however.

If you have a float-switch-controlled well pump, you don't want a filter deadheading the pump. There would be ways around that, including an pressure relief valve.

 

[Sponsor]

 

[LLigetfa]

Storage tanks are often deployed when the well cannot supply peak demands. Backwashing and regens might be too much of a demand on the well. Granted, it is possible to rig solenoid valves to use the stored water for backwashing/regens but it adds complexity.

 

[LakeDwellerMN]

I saw storage tanks used in locations like LLigetfa mentioned, where demand can exceed the pump/supply capacity for a period fo time. I saw this in a town in Mexico where the church added one in an attempt (successfully) to address that very issue.

Sediment and cleaning was handled through a system that was added to the tank when it was installed. It was only 500 gallons and there was an agitator (as I recall).

That said, storage tanks should NOT be thought of as a "clean" water source (in of themselves). There was a coarse filter coming from the well (instead of a spin down) to help with some things. I don't recall all the mechanism that were involved, sorry. I do recall there was a "float" that would call for water from the well when it got below a certain level.

They added a 3-stage BIG blue (4.5x20) filter setup along with UV lights to treat the water before the building plumbing. Church members would fill 5-gal jugs on Sundays.

 

[Bannerman]

An initial storage tank is often the first stage of the water treatment system, thereby reducing the load on subsequent treatment systems, and may eliminate the need for further treatment.

When a storage tank is open to atmosphere, the oxygen from the air in contact with the water within the tank can cause ferrous (dissolved) metals such as iron and manganese within the raw well water, to become oxidized, thereby converting them to a ferric (solid - undessolved) state. Most ferric iron and maganese will then precipitate to the bottom of the tank and accululate as sludge which will need to be routinely removed.

To further improve oxidation, the incoming flow will be often sprayed using a nozzle at the top of the tank so the resulting water droplets will have more thorough contact with the air located above the water surface.

Depending on the conditions of the raw well water and the effectiveness of the initial oxidation, further treatment requirements will usually be substantially reduced.

 

[LLigetfa]

An initial storage tank is often the first stage of the water treatment system, thereby reducing the load on subsequent treatment systems, and may eliminate the need for further treatment.

What you describe is an aeration tank which is intended more as pre-treatment than storage to compensate for a low producing well. They are often used to mitigate stinky water.

 

[Bannerman]

What you describe is an aeration tank

An atmospheric storage tank is often utilized for both applications.

 

[Blamus]

I'll likely need pretreatment and storage!

I just had a 800ft well drilled. They then installed the PVC liner, and the water line to the house.
The driller said they reached water at 730ft, and went down to 800ft. 28G per hr, so very low, and told me to frac. So I fracked.
The fracking company said when they opened the well cap they saw water at 100' level. They then pressurized every 100'. They said they saw a pressure drop at 200', but nowhere else.

The pump has not been installed yet. So still have yet to do another flowrate test and water analysis. But they told me to expect very hard water. I know everything smelled of sulfur. Moreover, Neighbors have told me to expect significant seasonal changes to available water. Most of them have large cisterns and advised me to do so. Though they all have shallower wells (when their houses were built in the 60s, people only went 300-500ft. A few of them simply don't have wells, just a large enough cistern and truck in water monthly. Some of them have water treatment but still buy their drinking water, and use well water only for non-drinking use. This is the Colorado Rockies.

My fracker said if my water is at 100ft, then i have 1000G of storage just in the well. And assuming I improved the flowrate some, I can probably get away without a large cistern. 3000G would be recommended if my well was dry. My well service people also think that I don't need a cistern since I fracked, but we still don't know the post frac flowrate yet.

My driveway (where the well is) and the garage (where all the well equipment will be) both are just dirt right now. Will pour concrete at the end. But since we are excavating and grading still, it would be of almost no additional cost to dig a large hole somewhere in the garage for a cistern if I want. So that's why I'm thinking very seriously about adding one now. I guess now that I think about it, if I loose power my pumps wont work anyway so doesn't matter if I have clean water stored or pre treated water stored. i'll have no water either way! Maybe having a cistern as pre-treatment and storage makes sense. Would this pretreatment tank make my garage and house smell of rotten eggs?

The well company suggested a 300G holding tank after the well, because the well pump won't have enough flowrate for the house. I think then there would be another pressure tank and then softeners etc. I will ask them about installing a cistern (2500G seems like a common size?)

I imagine an under sink reverse osmosis unit for the kitchen might be nice.

 

[WorthFlorida]

...... of almost no additional cost to dig a large hole somewhere in the garage for a cistern if I want. So that's why I'm thinking very seriously about adding one now. ........I imagine an under sink reverse osmosis unit for the kitchen might be nice.

Before burying a storage rank under the garage floor, check building codes of it is allowed. Concrete plus the weight of a vehicle maybe more weight that a tank can support. Cisterns buried outside can collect rain water from your house gutters. It'll just will give you more options.
For RO systems, they can use 3-20 gallons of water to make 1 gallon of drinking water. Typically, an under sink unit holds about 2 gallons water. the 3-20 gallons of water just goes down the drain.

 

[LLigetfa]

My fracker said if my water is at 100ft, then i have 1000G of storage just in the well.

Also, 28 gallons per hour is 672 gallons per day. Most households don't use that much water in a day.

 

[2stupid2fixit]

One advantage of an atmospheric tank is that sediment settles and H2S can go away. You do have to remove sediment after a while however.

If you have a float-switch-controlled well pump, you don't want a filter deadheading the pump. There would be ways around that, including an pressure relief valve.

I slept through lots of chemistry classes but I remember some stuff from REM sleep. If I remember right, water is softened with salt. Calcium chloride or something. I dont remember the electron shell diagram or what covalent bonds it forms but i DO remember that salts generally accelerate electrochemical degradation of rubber and neoporene and the other petroleum (think of the carbon chain) things that are used to make the bladders in pressure tanks AND the coatings in storage tanks. I would think the treated "softened" water would be intensely more agressive to the bladder and liner material. Just a speculation. Id put every water holder inline before a treatment or softener, if possible, using my own side of a soup can advice.

 

[Reach4]

Softener salt is usually NaCl, which has ionic bonds. KCl is the expensive alternative for those who want to avoid sodium.

The calcium and magnesium, that softening removes, also form salts. Those are easier on concrete, which is only one of the reasons they tend to use calcium chloride on roads. Plastics don't get bothered by either. A lot of atmospheric tanks are polyethylene.