A Laing D5 was installed in place on the reservoir, and this reservoir/pump was connected to a very simple loop consisting of it and tubing/fittings connecting the marked outlet port to a calibrated liquid flow meter and back to the marked inlet port, and a Dwyer 490-1 wet-wet manometer with the high pressure and low pressure ports between the inlet and outlet of the pump to measured the pressure drop across it (the loop had a valve to help increase/decrease liquid flow restriction easily). Distilled water used for testing and the pump was fed 12 VDC constantly. In order to test how good the Alphacool top was, the same P-Q tests were performed except with the same D5 pump with different D5 pump tops:
The D5 top in the Heatkiller Tube is a good performer overall, better than the stock Laing top and offering very good max head pressure while having a lower than average max flow relative to other aftermarket pump tops. It will fare well with slightly more restrictive loops than other D5 tops, but not enough to where it alone merits a strong consideration. For those looking to save space by having an integrated pump top in the reservoir, this will do just fine.