Side view of MCP600 pump with attached tubing
SwiftTech MCP600 (cola can for scale)
click photo to enlarge

THe pump I chose to use is the SwiftTech MCP600, a pump specifically designed for continuous use in computer water cooling. The main housing of the pump is machined aluminum with a very nice metalic-flake blue paint. It feels very solid and well made. The impeller housing is made of a very solid and durable plastic, and allows for a completely nonmetalic water path (important for corrosion resistance). It is designed for continuous inline operation (not submerged). The basic specifications are:

Nominal voltage: 12V DC
Nominal power: 9 W
Maximum head (force): 2.2m (7.2ft)
Maximum discharge (flow rate): 600 L/hr (160 gal/hr)
Hose connections: 1/2 inch hose barbs (~10.5mm I.D. / 12mm O.D.)

Among pumps of its size the MCP600 is actually fairly powerful. It may not have the fastest flow rate, but it has plenty of force. The following photographs show some additional views. The soda can was placed next to it so you can get a sense of scale. The pump itself is roughly 4x4x3 inches, or 100x100x75mm.

Top view of MCP600 pump Face view of MCP600 pump with attached tubing

Preparing the pump for its breakin period

The pump should be run for a while before it is actually used to cool your computer. This is to test it not only for leaks or defects, but also to allow the bearings a breakin period. The bearings actually may be a bit noisy until broken in, which Switech says can take up to 24 hours of operation (I'll have more on that later).

I found the easiest way to break in and test the pump is to do it outside of the case and keep it as simple as possible. Besides the pump you will need a few feet of tubing (1/2in I.D.), a jug of either distilled or dionized water (not spring or generic bottled water, and not tap water), an ATX power supply, and a large bowl. The following shows the setup I used (the power supply is out of picture).

Initial pump priming setup

You will want a fairly short piece of hose (1-2ft) to attach to the pump intake (the horizontal inlet going into the center of the housing). Attach the rest of your hose to the outlet (the vertical pipe tangential to the housing edge). Clamp both hoses securely with the metal worm clamps that came with the pump.

Since this pump runs off your power supply rather than a wall outlet you will need to have an ATX power supply nearby. The tricky part is that ATX power supplies are designed not to turn on unless there is a motherboard attached to them. But it is fairly easy to trick it with a simple paperclip. Find the ATX motherboard plug (the biggest one with the most wires) and you need to short circuit the only green wire with any of the black ground wires.

Bypassing an ATX power supply no-load detection to force it on

Do not turn on the power yet. With the power supply ready and the tubing all connected you are now ready to prime the pump. Priming insures that when the pump is first turned on that it's impeller wheel is sitting in water and not air. You can very easily damage most water pumps, including this one, if you run it dry (meaning just pumping air). There are two common causes of dry pump damage: the motor turns too fast without the resistence of the water, or the pump relies on the water for its own cooling or lubrication. Besides, water pumps are very poor at pumping air, so if the intake tube is not already filled with water the pump won't be able to suck hard enough to bring it in.

Side note: initally I had planned on using an old junk 200W ATX power supply. However I found that it could not power the pump. Like most electric motors, the pump will draw a very large surge current the moment it is turned on, and that was enough to cause this poor power supply to go into automatic short-circuit protection shutdown mode. Nothing was damaged, but I had to get my newer larger power supply to make the pump work.

Priming and turning on the pump

Put the end of the discharge hose in the bowl, unless you feel like flooding the room. Then mostly fill the bowl with distilled water (but not to the top or you'll make a big mess). Now hold the intake hose up so it's end is higher than the pump. Fill the tube as best you can with water, making sure that the whole tube all the way to the pump intake is filled. Having small bubbles is okay, but you don't want any large air pockets (areas where the whole cross section of the tube is just air). While you do this some water will leak through the pump and start coming out of the discharge hose. This is fine, but just means you'll have to pour fast enough to keep up.

When the intake hose is completely filled seal the end with your thumb to keep air from entering. Then place the end down in the bowl so it is below water, at which point you may remove your thumb. The most important thing throughout this whole process is that you should never let the intake hose suck in air! So be sure it is held under the water line securely and that the bowl has enough water to finish filling the rest of the discharge tube and not become empty.

You are now ready to turn on the power supply. Be sure you're holding the hoses so they don't go flying out of the bowl, and always be ready to immediately turn off the power if the pump starts running dry. Also don't be surpised at the flow rate, it will be fairly fast, so it you aim the hoses upwards you will spray you walls. Rated at 160 gallons per hour, thats quick enough to fill a gallon jug every 30 seconds or a liter bottle every 10 seconds.

When you turn on the power things will get moving. Initially there will be a racket as the hose and pump housing will still have small air bubbles in them. This will sound like loud gurgling or growling, but should start to smooth out in a minute or so. Small bubbles won't hurt, as long as water is still flowing. I found that you may need to rotate the pump around a bit to help get all the air out. Also for this pump it also helped to turn of the power for a few seconds several times, as it seemed that some air bubbles were trapped inside the pump and would not come out while it was operating.

Eventually nothing but water will be flowing and you should not see any air bubbles traveling throught the hose. In fact it should be difficult to even see fluid movement inside the hose itself. However the bowl will be quite agitated. After everything calms down just let the pump run for several hours. Do however keep an eye on it, because if that intake hose ever pops up above water it won't take long before your pump is killed.

Water turbulence in bowl during pump priming

What about the noise?

The pump may make some unexpected noises during this initial breakin period. Once you get all the gurgling noises caused by air bubbles gone you will then be able to hear the motor and bearings. Mine had an unusual rhythmic pattern that alternated between loud and quite every second or two. But it slowly became quiter and went away altogether after about an hour. After that the pump was just making a solid continuous mechanical-sounding hum. This hum will always be present, but will continue to decrease in volume over the next several hours until it is comfortably quiet.

Do realize that the pump will sound louder as it sits out in the open on a table than when you eventually mount it away inside your computer case.