These systems have the following advantages:

• They are simple, cheap and easy to install compared to most active systems.
• They offer more collector placement options than an ICS setup.
• They can run on a PV-powered pump.
• They are extremely efficient when in operation.

It's also important to consider the disadvantages:

• There provide no freeze protection at all.
• They are susceptible to mineral buildup from hard water.
• Some of the specialized components are less reliable than standard equipment.
• They waste a small amount of water every time they switch off.