Blog    |    Determining Appropriate Poly Tank Size For Your Operation Space

Poly Tank Size

In the industry of storage, there is no place for the phrase “one size fits all.” The object is to produce customized products that fit every conceivable size and function for as broad a customer base as possible. That is the ideal anyway.

Fortunately, real estate developers often make this task easier for both poly tank manufacturers and their patrons. As you go driving through town, you may notice houses of approximately the same size nested together in one neighborhood. A little further down you may see a series of apartment complexes. You may have a gated community with bigger, more expensive houses that are all a bit larger than other places in town. Later you may pass by an industrial park with warehouses or a shopping center with stores and offices.

These locations all share similar sizes and functions, allowing poly tank manufacturers to mass produce commonly purchased poly tank sizes and also to recommend specific poly tank sizes to match typical customer needs. Often poly tank size and function go hand-in-hand. That means if you know what kind of purpose you have for your poly tank, and you know what kind of area you have to keep it, you can quickly come up with the size of tank you require.

Poly Tank Size

Large Tanks and Their Functions

Large tanks perform large functions. Or, perhaps a better way to think about them is that they perform everyday functions – things we cannot live well without.


One of the most common types of large poly tanks is septic tanks. They come in a variety of sizes for both urban and rural usage. Their purpose is to store wastewater and often expel it out into a draining field where the water is then filtered and completely cleaned before returning to the groundwater system. There are different types of septic tanks that either drain by gravity or by electronic pumps positioned within them. Most poly septic tanks must be kept partially above ground, but some metal septic tanks can be buried entirely if local regulations allow their use. All of these factors may influence the shape of a poly septic tank.

Poly tank size for septic tanks is much easier to determine. Since septic tanks have to do with water regulation in a household, you need only find out how much water your household (or place of business) uses on a daily basis. You can find this out by looking at your water bill or monitoring your intake water pumps. Whatever water enters into the system is going to go back out eventually. Then you take the standard sizes for septic tanks. A 1 to 2 bedroom house requires a 750-gallon poly septic tank. Each additional bedroom adds about 250 gallons to the tank size up to six bedrooms. If you happen to use a large amount of water that will run through the septic system, you may need to consider larger poly tank sizes there as well.

Drinking and Other Water Storage

Another frequent use for poly tanks is storing water. Some store large amounts of drinking water and use measurements and tablets to keep the water purified for drinking. If you choose to use poly tanks for drinking water, it is crucial that you buy poly tanks made from UV resistant plastic, so your drinking water does not get contaminated. Most drinking water tanks are smaller in size, but if you have a business that requires stored drinking water, take into consideration that most people need to drink about half a gallon of water each day for drinking and also for cooking purposes. Consider how often you can refill the tank. If you can only fill it once per month, you will need a tank that holds approximately 16 gallons per person.

Most people do not store drinking water in large-scale tanks, but more and more are beginning to save water for household cleaning utilities. Some of these reasons are environmental, and some are economical. Regardless of their reason, these kinds of tanks need to be bigger than drinking water tanks.

Most people use 1 gallon of water each day – half for drinking and half for cleaning. That is an easy formula to use when determining your poly tank sizes for general water storage. If you are able to refill monthly, then you need a tank that can hold about 30 gallons per person in your household. With cleaning and sanitary water, however, it is doubly important to err on the side of caution. What will you do if you host Thanksgiving dinner for your family and suddenly the water tank goes dry, and you can no longer wash dishes or use the restroom? It is always better to double the amount of water per person to account for hosting any guests in the future. This means you need at least 60 gallons per person per month.


The third form of large water storage tank that you may need help determining poly tank sizes for is in irrigation tanks. Whether you have indoor or outdoor gardening, this is water that is often treated with plant nutrients to help them grow faster and better. The size of this tank will be determined by the size of your garden. How much water do your plants need? You can multiply their weekly need by 52 and divide that number by 12 to determine an accurate monthly water need. Again, this assumes that you are able to refill the tank entirely each month. If you cannot, you will need a tank that can hold two months of water in it.

Small Tanks

Poly tanks have some competition with metal and even concrete when it comes to large tank sizes, but you cannot compete with the lightweight, sturdy, and durable nature of plastic when it comes to small poly tank sizes. You cannot beat them for their low price and convenience. Because of this, there are two prevalent uses for small tanks: Gasoline and emergency drinking water storage.


Gasoline is categorized as a hazardous material and therefore can only be legally contained in small containers without special permits. Five gallons is usually the maximum you can keep per in any one building. The reason for the quantity limit on gasoline is that if it catches on fire, there will be less explosion in one home if gasoline is kept to a functional minimum as a safety precaution.

Emergency Drinking Water Storage

While some people used poly tanks to store regular drinking water, most people save drinking water just for emergencies. One of the popular ways to keep these has been in stackable “brick” water tanks. These are small poly tank sizes that only hold a gallon or two in them. The flat, rectangular sides and stackability are why they have been often referred to as water bricks.

As mentioned earlier, if you hope to use poly tanks of any size for drinking water storage, you must be sure to have them made with UV-resistant polymers, so the water does not get contaminated over time. It also helps to keep them out of direct sunlight.

Medium-Sized Needs

What do you do if your storage need is not something that requires 1000 gallons of water, but needs more than 5 gallons as well?

First, determine your storage capacity required by how much you need to have available multiplied by the amount of time you need it to cover before refilling. Then measure the amount of space you have available. You may discover that you have a greater need than area available. If that is the case, you will have to readjust your plans. Perhaps you will need to find ways to refill your tank more frequently. Maybe you will need to look at the option of purchasing multiple tanks and swapping them in and out of a specific location.

When considering space for poly tank operations, consider the shape of the tank as well. Rectangular-shaped tanks take up less space than rounded ones according to size. They also may be stackable, depending upon their weight and contents. However, round poly tanks can be rolled and perhaps transported easier when filled, and rectangular tanks often need a support structure to help prevent the sides from bowing. It is also crucial to consider just how much they will weigh when they are filled. Will the floor or wall space they inhabit support them? Will they need to be transported when full?

As you can see, there are many factors involved with determining your poly tank sizes and the decisions you have when purchasing them. Consider the function of your tank. Take into account how much it will be used. Remember to factor in how often it will be refilled (or emptied). Find out if there are any local laws or policies regarding the use of your poly tank on your property. Measure just how much space you have available for your tank. Finally, be sure to plan ahead and get a tank a bit larger than you currently need. Think about the future and your plans for growth. Lastly, keep in mind that if your space is oddly shaped or changes, multiple smaller tanks are always an option.

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