Pump Top Testing

With the pump isolated and tested, it is now time to see how the Bitspower D5 top itself performs. To do so, I used the same pump on various Xylem D5 tops from various companies; some standalone, some integrated into reservoirs. The testing methodology to generate a P-Q curve was the same as before, though with only a 100% PWM duty cycle this time around.


There is a fair amount of variation from top to top, with some focusing on providing a higher maximum head at the expense of flow rate and others going the other way. A good balance of the two overall ends up being the best in realistic scenarios, and it is here the Bitspower D5 top disappoints. I will say that the first Bitspower D5 mod top I tested a few years ago consistently performed worse than every other top, including the stock Xylem top, so this is still an improvement. Regardless, I can only hope that the newer Bitspower tops perform better than this one.

A Realistic Loop Test

So far, we have seen the results for extremely controlled tests, often to minimize the effects of involved variables. However, this does result in an incomplete picture by focusing on the possible maximum as opposed to realistically achievable values. Take a pump's P-Q curve, for instance. The Xylem D5 is rated at 1500 LPH (liters per hour, 6.6 GPM) of maximum flow, which is great to look at but corresponds to an open loop with no liquid-flow restriction. Close the loop and it is reduces to a much lower value depending on which pump top is used. Add in your everyday closed-loop components and you are looking at a maximum flow rate of ~1-1.2 GPM for most people. This is where the budget pumps come in and why you should consider all options.

I used an XSPC Raystorm Pro CPU block, Swiftech Komodo R9-LE GPU block, Black Ice Nemesis GTS 360 radiator, and two sets of Koolance QD3 quick disconnects to go with six Bitspower 1/2" x 3/4" fittings and Primochill Advanced LRT tubing of the same size. The blocks are one of the least restrictive in each category, and the addition of the quick disconnects and more restrictive radiator brings the average restriction close to what most loops would have. I have tested the aforementioned pumps, including the Swiftech MCP50X which makes a comeback here. At the same time, I measured pump noise alone by placing the setup inside an anechoic chamber at 19 dBA, with a sound probe 6" from the pump. No other sound source was inside the chamber when these measurements were taken.


Things get a lot closer here, and the Bitspower D5 Vario does a good job at keeping things flowing at a low noise level. It is bested by the Alphacool VPP755 at the higher end, also terms of noise, but the Alphacool VPP755 does not have the proven long-term reliability the Xylem D5 enjoys yet. There are a few more budget pumps that do a decent job on a performance/noise basis, but those wanting the best-possible performance at reasonable noise levels will look at the Xylem D5, which makes the Bitspower offering a strong option.

Given the nature of so many moving parts inside a pump, reliability is hard to talk about within a review's time frame. It is thus helpful that the Xylem D5 and DDC have both been in use for years in some of my systems and that of others. The D5 especially has lasted through the test of time, and this is another plus for this Bitspower product. Since there are so many hard-to-quantify variables when it comes to a pump, I will refrain from making an attempt at a relative performance chart and, as such, a price-to-performance chart as well.