{"id":887,"date":"2023-03-03T13:41:32","date_gmt":"2023-03-03T19:41:32","guid":{"rendered":"https:\/\/www.ntotank.com\/blog\/?p=887"},"modified":"2023-03-03T13:41:33","modified_gmt":"2023-03-03T19:41:33","slug":"tank-definitions","status":"publish","type":"post","link":"https:\/\/ntotank.com\/blog\/tank-definitions","title":{"rendered":"Rain Tanks | Tank Definitions"},"content":{"rendered":"\n
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In rainwater harvesting, a rain catchment system and tank are each made with a select set of parts, equipment, and accessories. In this Rain Tanks Series: Tank Definitions, we will look at and define the different parts of a standard rainwater collection tank. This post will focus primarily on vertical, above ground polyethylene storage tanks, like those found here<\/a>. <\/p>\n<\/div>\n\n\n\n

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The post is intended for do-it-yourselfers (DIYers) and fledgling rain harvesters new to the practice. If this sounds like you, \u201cWelcome,\u201d and it\u2019s great you’re here and that you have an interest in practicing rainwater harvesting as an alternative water supply, for conservation, and together for our environment.<\/p>\n\n\n\n

Parts of a Rain Tank<\/h2>\n\n\n\n

There are five (5) main parts to a complete, standard polyethylene rain tank. These five parts are the cistern itself, the manway, the overflow, bulkhead fitting(s), and the base foundation. <\/p>\n\n\n\n

The Cistern<\/h2>\n\n\n\n

The word cistern is an old term that has been around and used throughout history, and refers to a watertight vessel or area used to store and provide water as needed. A cistern can be above ground or underground, small or large in volume, made of plastic, metal, or the earth and earthen materials. Here, we are discussing bulk volume, above ground storage tanks made from linear polyethylene as it is one of the most common and modern material options for rainwater harvesting. <\/p>\n\n\n\n

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Plastic rainwater cisterns are manufactured from what is known as linear high-density polyethylene, sometimes abbreviated HDPE, HDLPE, or poly. While this may raise questions or concerns for health-conscious individuals and environmentalists, polyethylene rainwater tanks are made using only premium quality materials that have been approved by the U.S. FDA (Food & Drug Administration) for health.<\/p>\n<\/div>\n\n\n\n

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Many polyethylene rainwater cisterns are also additionally certified to ANSI\/NSF 61 standards for potable drinking water. The American National Standard Institute (ANSI) and National Sanitation Foundation (NSF) Standard 61 is a nationally recognized approval guaranteeing a product is safe for drinking water. This means a poly cistern is 100% safe and approved for the long-term storage and provision of clean, drinkable water and will not affect water quality in any way. <\/p>\n<\/div>\n\n\n\n

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The cistern <\/strong>serves as a reservoir in rainwater harvesting to store rain as it is being collected and hold the rainwater until it is time for it to be used. Above ground poly rainwater cisterns most often range in size from 100 gallons to 10,000 gallons of water storage capacity. They are traditionally made and offered in two types: cylindrical and slimline. Cylindrical rain tanks<\/a> are circular in shape and are an overall good, go-to choice for rainwater harvesting. Slimline rain tanks<\/a> are also known as doorway tanks and are rectangular in shape that makes them ideal for placement along walls and fences, in locations cylindrical tanks may not fit, and simply to save space.<\/p>\n\n\n\n

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Slimline Rain Tank<\/figcaption><\/figure>\n\n\n\n

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Cylindrical Rain Tank<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

The Manway<\/h2>\n\n\n\n
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In many rainwater harvesting setups, the manway<\/strong> serves as the main entry point for rainwater flowing into the cistern for collection. By definition, the manway is the opening on the top of the tank used to allow access to the tank interior for inspection and maintenance. In rainwater harvesting, the manway is commonly used as the primary inlet for collecting rain as it flows through the system to the cistern. <\/p>\n<\/div>\n\n\n\n

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Tank Manway<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n
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Rain tank manways are often larger in size to provide a better opening for rainwater inflow, making system setup easier and reducing potential water loss from spillage. Many polyethylene rain tanks available for purchase commercially include a tank screen<\/a> accessory designed to fit within the manway and filter out debris in the rainwater.<\/p>\n<\/div>\n\n\n\n

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Tank Manway with Tank Screen<\/figcaption><\/figure><\/div>\n<\/div>\n<\/div>\n\n\n\n
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The manway does not have to be used as the rainwater collection inlet. A rainwater harvesting tank and system can have piping directly plumbed to the storage cistern at a bulkhead fitting or through the tank wall by way of drilling a hole. <\/p>\n<\/div>\n\n\n\n

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Directly Plumbed Rainwater Cistern<\/figcaption><\/figure><\/div>\n<\/div>\n<\/div>\n\n\n\n

When discussing the manway, it should be mentioned that no one other than a licensed professional should ever enter a storage tank for any reason due to safety hazards.<\/p>\n\n\n\n

The Overflow<\/h2>\n\n\n\n
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In a rainwater harvesting tank, the overflow<\/strong> is an important component used to manage excess water whenever the tank becomes full. The overflow is simply an open port located near the top of the rain container that provides a dedicated location for excess rainwater to \u201coverflow\u201d from the tank. <\/p>\n<\/div>\n\n\n\n

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Rain Tank Overflow with Air Gap<\/figcaption><\/figure><\/div>\n<\/div>\n<\/div>\n\n\n\n

The overflow port allows excess water to be managed in a controlled way. Without an overflow, excess water would pour out from the manway or any other opening and flood around the tank base. <\/p>\n\n\n\n

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Proper installation and use of an overflow will direct the excess rainwater away from the tank base as well as the foundation of any nearby structure. This recommendation exists to prevent erosion around the rain tank\u2019s foundation and to prevent any damage that can occur over time from large volumes of water concentrated at a set location.\u00a0<\/p>\n<\/div>\n<\/div>\n\n\n\n

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A tank overflow port is a pre-installed standard on most rain tanks for sale and comes ready for setup and use. The tank overflow port is often either 2\u201d or 3\u201d in diameter and can be easily connected to PVC piping to run the overflow water to wherever desired. Ideally, the tank overflow will put the extra water to good use watering nearby landscaping, lawns, or rain gardens. <\/p>\n\n\n\n

For large rainwater harvesting setups, the overflow can also be used to connect multiple rain tanks together. In a connected rain tank setup, the excess water from the first tank will overflow and be collected by the second tank rather than being discarded.<\/p>\n\n\n\n

For rainwater cisterns without an overflow, a tank outlet kit<\/a> can be purchased and easily installed to properly manage rainwater overflow.<\/p>\n\n\n\n

The Bulkhead Fitting(s)<\/h2>\n\n\n\n
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By definition, the bulkhead fitting<\/strong> is a through-wall plumbing fixture used to make pipe connections and allow liquids to flow from one location to another through a wall by means of a specified, leakproof hole, which is the bulkhead fitting. A bulkhead provides a secure location for connecting pipes, valves, and\/or hoses to a rain tank so harvested rainwater can be easily withdrawn when needed.\u00a0<\/p>\n<\/div>\n\n\n\n

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Rain Tank Bulkhead Fitting<\/figcaption><\/figure><\/div>\n<\/div>\n<\/div>\n\n\n\n

Most commercially available rainwater tanks include one (1) or two (2) bulkhead fittings pre-installed and ready for use. <\/p>\n\n\n\n