First Watercooling Loop

Reservoirs

Reservoirs are not necessary but are so useful that they are essentially a necessity to buy. Reservoirs help primarily with filling and bleeding the loop, particularly when coupled with fill and drain ports mounted to the outside of the case.

There are two main types of reservoir:

Cylinder reservoirs are large and can usually be mounted horizontally or vertically. The larger the length or fatter the diameter the more coolant they can hold. Like any reservoir the more coolant that can be held the more useful the reservoir is (up to a point). Vertically mounted cylinder reservoirs with a pump directly underneath are my favorite because of how easy they make it to bleed and fill the pump. The large volume of water above the pump provides a pressure differential and easily frees any air from inside the pump enabling it to start pushing water through the system. I would always recommend the largest vertical mounted cylinder reservoir you can fit (while still allowing space to easily fill it). Plus vertical reservoirs can look cool in cases with a window. Bear in mind that this usually requires a larger case. Space savings can be had on some versions by having the pump mate directly to the bottom of the reservoir. This can also save the cost of a top, but can also hurt performance. Example of a dual loop, dual reservoir setup mounted next to the motherboard:

The next most common reservoir is a bay reservoir. This typically will be a dual bay type which will take up two 5 1/4″ bays in the case. Some (but not many) cases may need to be modified slightly depending on the design. Most bay reservoirs are designed to save space and therefore normally try and integrate the pump into the back of the reservoir. This is very efficient space wise, but bay mounted pumps are notoriously difficult to fill and bleed. The case will usually require shaking in order to burp air out of the pump and the reservoir will need filling a bunch of times. Air will typically bleed poorly and performance of the pump itself maybe compromized by virtue of trying to fit so much in a small space.

Another reservoir that is worth a shout out would be something like the Swiftech micro-res – designed for small cases where a real reservoir can’t be fitted.