The pressure tank is just a reservoir of water to ensure stable pressure as the pump is not a constant pressure pump.
The situation without a pressure tank.
Let's say you open a tap at .5 gallons per minute, pressure will immediately drop and when the pump comes on at the low event let's say 60 psi pumping 5 gallons per minute. 10 times the demand, the pump will verify quickly reach the high event, we'll say 80psi and shut off. Back down to 60 on back up to 80 off. So on and off continuously and frequently. Maybe 15 times in a minute.
With a pressure tank
All things being equal, at 60psi the pump cuts in but the excess flow gets bufferd into the pressure tank. Once it reaches 80 psi and cuts out there is a reserve of water stored in the tank. The pump can remain of longer and once the low pressure event is reached and it cuts in it can stay on longer. Longer cycles are better.
All that being said, the actual volume of water transferring in and out of the tank isn't all that much. It's the water compressing air that gives you the buffer. But water does transfer in and out. If it's piped in far downstream where there is a pipe reduction or sidewall restriction due to length there will be a lag in the flow causing fluctuations in pressure. Depending on the specifics of how it's piped in, it's possible to have hot and cold water stacking due to cold water being pumped into the hot side of the system.
So in reality it not absolutely critical to have the tank first but it is conventional and more sensible. Even if you had a leak it's problematic. Let's say you have a bad leak in your 1st fixture before its shutoff. Which valve downstairs do you close? The one just upstream of the pump? Where is the pressure device? Can the pressure drop from the leak now cause the pump to dead head into a closed isolation valve? You still need to isolation the tank from the other side of fixture number 1. Are these things you want to be thinking about when you have a big leak happening?
People are moving in and out of the cities every day, and there is a growing need for storing even basic things like water. Whether you are looking for septic solutions, drinking water ideas, irrigation needs, or a large reservoir for some indoor gardening, a water storage tank is probably part of the system you will need.
Once you’ve decided that you need a water storage tank, the next problem becomes where to put it. Should you place your water storage tank above ground, where it will be easy to access? Or should you put your water storage tank underground, where it may be less conspicuous?
Underground storage tanks are categorized as a tank and its connecting underground piping which holds at least one-tenth of its total volume beneath the ground. Underground storage tanks are an excellent choice for anyone who wants to save space and maximize their property use. They save space because they are underground. You can even install these tanks under lawns and driveways, which frees up additional land for more productive uses.
Underground storage tanks are also suitable for people who want to reduce the risk of damage from vandalism. This may not be a big concern in your neighborhood, but not all damage has to be on purpose — an above-ground water tank could be damaged from something as random as a car crashing into it.
Another important consideration is that they generally corrode and deteriorate much slower, particularly if you are using a metal tank. This is important especially if your water tank will be hooked up to an auto-fill system, as any leaks that develop could easily go undetected for weeks until your next water bill comes in, and by then you’re on the hook for hundreds of gallons that you didn’t use!
Water storage tanks underground are also an excellent choice for those who want to store vast amounts of water, as a very large water tank can be difficult to find a good spot for above ground. They are protected from vandalism and theft and face a low risk of damage due to extreme weather events like hurricanes and tornadoes. The most significant benefit is that water storage tanks underground do all this without visually impacting your landscape.
The popularity of water storage tanks above ground is on the rise. The increase in above ground demand is primarily due to their lower initial costs. They require significantly less digging, filling, and paving than storage tanks underground, so they are much easier and less expensive to install. You may need a truck to bring it in, but you will not need a backhoe to get it set in its place.
Water storage tanks above ground can quickly be checked for leaks visually and are usually easier to access if repairs are required. Because of this, you are much less likely to end up paying for gallons upon gallons of water leaking out into the surrounding soil.
However, you will need to check with your local regulations and fire codes because they will determine whether you are eligible for a water storage tank above ground. This decision is based on factors such as how much distance is required between tanks, between property lines, what the fire resistance level is on your property, and the water tank’s maximum capacity.
To qualify for a water storage tank above ground, you need to answer yes to all of the following questions:
If you are unable to answer yes confidently to all of these questions, then an underground model of water storage tank may better suit your needs and requirements instead of a water storage tank above ground.
Another significant factor to consider when choosing the location of your water storage tank is its construction material. If you are storing water, your tank can safely be made of metal or plastic.
Plastic (or Poly) tanks can be a little less expensive and lighter to install, but they are not built to be fully submerged underground. The pressure around buried poly water storage tanks underground causes them to crack, fracture, and leak. These fractures lead to the costs of digging them up and repairing, or more likely, replacing them.
Metal tanks, by comparison, hold up much better as underground water storage tanks. They are built to manage the underground pressure. However, metal water storage tanks underground have two main weaknesses.
The first is in their seals and connections with other pipes. As temperature fluctuates, different kinds of metals change size and shape at different rates. This variance in fluctuation means if you have a steel tank with copper pipes and brass fittings, these pieces will twist apart during times of changing temperatures. Fortunately, the temperature fluctuates less below ground, but it can still cause problems.
The second weakness is their susceptibility to rust and corrosion. Plastic does not rust, but metal can and does. Water storage tanks underground typically suffer significantly less rust and corrosion since they are protected from wind and rain exposure, as well as other environmental effects, but they still may get wet from rainwater seeping down into the ground around them. Paving the field above and around your metal water storage tanks underground may be a good way around this weakness. However, it will also prevent you from being able to access your tank if an internal problem occurs.
If you are interested in a poly water storage tank and prefer it to be underground, there may be a compromise for you. You cannot just bury your poly water storage tank underground, but these tanks can be buried partially.
If you are interested in a partially buried poly tank, you will need to seek out an engineer who can evaluate your soil type, desired depth, and any other circumstances affecting the desired location of your tank. They can help you make sure that the foundation of your water storage tank is not eroded and is adequately supported. Without this help, the ground could erode unevenly and cause your tank to lean, fracture, and crack, spilling out all of its water.
You can usually bury a poly water storage tank underground up to 1 meter. You will need to dig your hole at least 12 inches wider than the diameter of your tank and prepare the standard foundations for them. Be sure the ground is compacted well and is level, so you have a flat base for your tank. Once you place the tank in the center of the base, you can fill your tank with water and fill in the surrounding area with compacted crusher dust and cement (3 parts to 1 part). Do it slowly, no more than 10cm at a time. When completed, you may want to put a fence around the tank to help protect it from outside interference.
Wherever you decide to place your water storage tank, you need to be sure to do some research, get some expert advice, and do it right the first time, so you don’t waste your time and money. These projects are not quick fixes and require proper maintenance, even if you have a water storage tank underground and out of sight. Out of sight, out of mind, only leads to complicated problems down the line.
Don’t know where to find the information and help you need? Your local water tank retailer and manufacturer would be a great place to start. They will know the strengths of their products. They will also recognize the local regulations regarding water storage tank installation. Also, it is likely that they will have experience adapting their products to a variety of property settings, and they will give you an honest answer about what will and will not work; after all, the success of your water storage tank is one of their primary means of advertising to the rest of the community. Any information they do not have on hand, they will likely have access to through their business networks. Speak with the professionals at GoToTanks.com to get their expert opinion on what type of tank and whether you should have your water storage tank above ground or underground today.