THE 3 PARTS OF A MISTING SYSTEM

part 2: Water Lines & Connectors



A portable misting system cools off in the field

If you'd like to put together your own misting system, expand one you already have, or would simply like to understand how one works, this series is for you.

It can help to understand the workings of a misting system by realizing there are 3 basic components:

  1. the misting pump
  2. the water lines & connectors, which we talk about here
  3. the nozzles

We've devoted a separate page to each component.

About the Water Lines

Water lines -- pipes, tubes, hoses, cables, channels -- "deliver" the water from the supply source to the nozzles. In hopes of avoiding confusion we'll use the general term "lines". The main considerations for the water lines are size, material of construction, and water pressure rating.


Sizing

A misting system uses narrow water supply lines to take advantage of available water pressure. These supply lines are sized based on the diameter of the line. Most supply line material is measured "nominally", which is an average diameter along the length of the line. The sizing used in misting systems is fairly standard. 3/8" and 1/2"/ 9mm and 15mm diameters are the most commonly used. 3/8"/ 9mm is typically used for all basic systems. 1/2"/ 15mm is used for large industrial projects where much more water flow is needed.

Thicker walled lines have greater durability and higher pressure tolerances as well as greater cost. Wall thickness does not affect line size (diameter). 1/2"/ 15mm L copper (thin-walled) has the same outer diameter as 1/2"/ 15mm K or M (medium- or thick-walled) copper. The same applies to plastic. The diameter stays the same on the outside, but the inside gets smaller as the walls get thicker. As a result, water volume in the line will decrease slightly as wall thickness increases. This may be helpful to be aware of, but will have little effect in a misting system.

Style: Flexible or Rigid

Flexible lines can be very easy to work with and install. They need no special tools and allow for virtually any nozzle spacing -- just cut the line wherever you want to place a nozzle. They can also be a perfect choice when setting up a misting system in hard-to-reach areas, or is situations where the tubes must make several bends and turns. Flexible tubes also allow for flexibility in the overall design of the misting system because nozzle spacing can be decided on the spot, and because sections can easily be removed and re-configured.

Flexible materials may be made of various plastics or nylon and might or might not be reinforced with braiding. With any flexible tube, be careful not to bend it into too tight a curve. It can kink the tube and diminish or completely shut off the water flow. Flexible lines are available in stock lengths as short as 24 inches / 61 centimeters or as long as 500 feet / 152 meters. Some are treated to withstand outdoor exposure by being treated with a UV protective coating. Flexible lines cannot be painted, but are often available in more than one color to blend with the surroundings.

Rigid lines range from plastic, such as PVC to copper to stainless steel. Rigid lines make a neater looking installation and can be painted or powder coated to blend in to the surroundings. Rigid lines also stabilize the nozzles so origin of the spray remains constant. Rigid lines can be compression fitted like flexible lines, or solvent welded for long-lasting leak-free connections. Often a combination of flexible and rigid lines are used -- flexible around obstructions and rigid for a neat appearance where visible.

Line Materials

The selection of line material is based on water pressure, flexibility needs and durability requirements. All are rated to withstand certain ranges of water pressures. Some of these can only be used with Low pressure, but others can be used with Medium or High pressure. Make sure your choice is rated to work with your misting system's pressure.

Following are some materials that may be used for lines in a misting system.

Plastic / Thermoplastic

Compared to copper lines, plastic is lightweight, easy to work with, doesn't corrode and may be priced about 75% less. Most plastics stretch and contract to accommodate variations in water temperature. Plastic lines, especially flexible lines, are great for a portable misting system because of their light weight. Some plastics can be joined with solvent fittings, other can only use push-in fittings or compression fittings. There are many kinds of plastics used for these lines. Here are the most popular:

PVC (polyvinyl chloride) and PE (polyethylene) lines are ideal for outdoor misting systems. PVC lines are rigid, PE lines are flexible and cannot be solvent welded. Both are low-cost and very easy to install. They will not rust or corrode; and have insulative qualities that prevent condensation from forming on pipes carrying cold water.

CPVC (chlorinated polyvinyl chloride) is another rigid plastic used for water supply lines that handle low water pressure loads. CPVC will last a long time, though is not quite as tough as copper, and can stand up to water with corrosive minerals.

PVC, PE, and CPVC are available in different wall thicknesses called "Schedules". The most commonly used wall thicknesses for a misting system are Schedule 40 (rated at about 300 psi / 20 bar), and Schedule 80 (rated at about 500 psi / 34 bar).

PEX is remarkably durable within a wide range of pressures. Flexible, it can be installed with fewer fittings than rigid plumbing systems. Works well for corrosive water conditions.

Kitec is a multipurpose pressure pipe that combines the advantages of both metal and plastic. Made of an aluminum tube laminated to interior and exterior layers of plastic, Kitec provides a composite line material for a wide range of uses, often beyond the scope of metal or plastic alone. Kitec is non-corroding, and stands up well to a variety of water compositions and extreme outdoor conditions.

Nylon

"Virgin" nylon is newly manufactured, which is much stronger that recycled nylon. Often UV protected, virgin nylon will withstand the most demanding outdoor conditions. Often used to route high pressure water from pump to copper or stainless steel mist lines, this flexible line can be directly clamped down or fished through conduit in the structure, in the ground or under concrete. Like other flexible lines, nylon can be fitted with simple push-in fittings or compression fittings. Nylon is typically rated up to 1000 psi / 70 bar, and is available in cut lengths, or in rolls from 100 to 1000 feet / 30 to 300 meters.

Copper

Both rigid and flexible copper lines are available. Rigid copper makes a neater installation for your misting system, but is much more difficult to install than flexible copper. it cannot be bent and must use elbow fittings to go around corners or obstacles. Flexible copper line is good for running around obstacles without connections or cuts. It can be joined by several methods, and is the only type of copper line suitable for flare connections. Pre-fabricated copper line is designed for quality and versatility and is a good choice when rigid lines and on-the-job customization are required.

Copper is available in stock lengths of 10 or 20 feet / 3 or 6 meters, and is also available in custom lengths. Copper is highly resistant to corrosion, but is becoming very costly. Copper line is available with three wall thicknesses: Type M is thin-walled, Type L is medium-walled and Type K is thick-walled. In most cases, Type L is used for misting systems and is rated about 1000 psi / 70 bar.

Copper should not be used if the water has a PH of 6.5 or less. The majority of public utilities supply water at a PH between 7.2 and 8.0 but private well water systems often have a PH below 6.5. When this it the case, installing a treatment system to make the water less acidic is a good idea.

Stainless Steel

Stainless steel lines are rated to 3000 PSI and are the ultimate for quality and durability. These lines can be powder coated and painted to match the surroundings.

Fittings / Connectors

A fitting isn't necessarily a physical piece of plumbing, but is a general term to describe any of a number of ways that sections of line are "fitted" or joined together. Fittings link together individual sections of the line, link the line to the water supply or pump, and link the line to the nozzles. Typical methods of fitting used for misting systems are:

Compression fitting is the kind that "screws" on with spiraling "threads" which are shaped at the ends of most water lines. These are perfect for the do-it-yourselfer. Compression fittings commonly have an outer compression "nut" or connector, and a "ferrule" or disk (also called an "olive" in the UK) that fits between the nut and the line. When the nut is tightened, it clamps down on the ferrule, forcing it to conform to the shape of the line and eliminating all space in the joint.

Over-tightening is the most common cause of leaks in compression fittings. If the fitting is overtightened, the ferrule will deform and cause leaks. As a general rule, a compression fitting should be hand tightened.

Compression fittings are easy to use and require no special tools or skills to put together, yet still provide water-tight seals that can withstand the pressures of a misting system. Compression fittings are especially useful when occasional disassembly or partial removal is needed, such as in temporary installation, since these joints can be disassembled and remade without affecting the integrity of the joint. Compression fittings are a good choice in confined spaces where soldering would be difficult or dangerous. But they are not as durable as soldered fittings, and should not be used where the fitting will be subjected to repeated flexing or bending.

Make sure compression fittings for all connections are properly rated. Secure all these fittings with Teflon tape. Check that all fittings are properly tightened.

Some compression fittings use "push-to-connect" or "slip-to-lock" hardware, which combine the compression nut and ferrule into one piece. They are simply pushed onto the line to form the connection. These are quicker and easier than standard compression fittings, but may be less secure.

Solvent fitting is typically used for plastic / thermoplastic lines. It uses a solvent matched to work with the specific type of plastic used for the line. The solvent is applied to the outside of the line end and the inside of the connector, and the two pieces are joined together while the solvent has temporarily dissolved the plastic of both pieces. When the plastic has re-hardened, the two pieces will have been permanently "melted" into a single water-tight unit. These fittings can be more water-tight and durable than compression fittings. Some plastics cannot be solvent welded and must be compression welded.

Crimped or pressed connections use special copper fittings which are permanently attached to rigid copper lines with a powered crimper. The special fittings, manufactured with sealant already inside, slide over the tubing to be connected. Thousands of pounds-force per square inch of pressure are used to deform the fitting and compress the sealant against the inner copper tubing, creating a water tight seal. The advantages of this method are that it should last as long as the lines, themselves, it takes less time to complete than other methods, it is cleaner in both appearance and the materials used to make the connection, and no open flame is used during the connection process. The disadvantages are that the fittings used are harder to find and cost more than sweat type fittings.

Sweat fitting is a means of joining copper tubing using "solder" (a fusible metal alloy) like a metal "glue". A sweat fitting is a smooth disk that easily slips onto the end of a section of the water supply line. The joint is then heated using a torch and solder is melted into the connection. When the solder cools, it forms a very strong bond which can last for years. With experience, sweat connections are quick to create, and when many connections must be made at once, sweat fittings can be quicker to join than compression or flare.

Flare fitting spreads the end of a line section be outward into a bell shape using a flare tool. Then a special "nut" compresses this bell-shaped end onto the next section of line. Flare connections are very durable and can remain water-tight for many years. But they are labor intensive and can be used with only a few misting line materials.

Interested in learning even more?

  • To learn more about how misting fans work with the weather, see our page on evaporative coolers.
  • To compare misting fans with other outdoor coolinsg solutions, visit our comparison page.
  • To shop for misting fans, visit our shopping page or these selected retailers:

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