Potted Eheim Pump Housing

Date Log; December 26, 2005

Most people who have been involved with liquid cooling their computers will have heard of the Eheim range of pumps. For many years Eheim have been held in high regard for their reliability and rugged construction. It is this reliability, created by Eheim, which has become a standard for others to follow.

Liquid coolers have in the past predominately favored the Eheim 1250 and 1048 models. These are 240 volt models and of course require a separate plugged connection. In recent years the emergence of 12 volt pumps which can be connected to the power supply have become popular. Eheim themselves have started to develop and market limited model versions of these types of pumps. Despite this there remain some passionate followers of the Eheim brand name who continue to rely on the 240 volt versions.

Eheim some time ago recognized the need for a smaller more compact range of aquarium pumps and started to produce the "Compact" range. The name of these pumps was graded by l/ph flow rate and head. These were set at 300l/ph (0.5 M head) 600l/ph ( 1.3M head) and 1000l/ph (2M head). Measuring in at a meager 90mm high, 40mm wide and 65mm long the Eheim compact series are tiny in comparison to their larger brothers the Eheim 1250 and 1048. Despite their small size these pumps pack a fair amount of pumping power into their small frame. By way of example we have had these pumps operating at -20 degrees Celsius during our water chiller trials and they came through that punishment without any adverse affect.

In Europe these smaller Eheim models seem to have caught on with the liquid cooling scene much more so than here in Australia. These pumps underwent quite a bit of a face change with the inclusion of modifications to convert the submersible Eheim Compact pumps to inline units. Some of the other modifications included the placement of the Eheim Compact pump in a small reservoir much as we have done here. This later modification was probably carried out to facilitate the filling and bleeding of the water cooling system.

The problem of filling and bleeding non reservoir connected pumps has plagued liquid coolers now for some time. This has put off many new liquid coolers as the complexity involved in filling and bleeding out the air often lead to discouragement and finally the abandoning of liquid cooling completely. Many of the larger manufacturer have recognized this issue and have attempted to solve the problem with pumps which have very small reservoirs attached to them. The problem with these is that they are often more of a hindrance than a help. To make the pump and reservoir compact enough inside the case the reservoir has had to shrink to levels where often it contains less than 100mls of coolant. Not much of a gain there.

We have looked at putting the pump and the reservoir together for a number of reasons. The first reason is to avoid the piddling little reservoirs, mentioned above, that are of little functional use. The second reason is that we wished to take any heat generated by the pump to the outside of the case where it can be displaced into the air flow. Some may say that this is an inadvisable move but we are of the opinion that the radiator size used with current liquid cooling is sufficient to warrant such a move.

The other reason for our interest in this range of Compact Eheim pumps is the need for a multi adaptable support pump for our testing. More than that we wanted to have a pump which would allow us the freedom to change barb size and mix and match the barb sizes used to evaluate flow rates and such like. With this type of arrangement we are also able to measure water flow temperatures inside the reservoir at will. Finally, we also wanted to be able to supply a pump which could be adapted to fill the need for a replacement pump in other less robust kits on the market today.

We started out, as we have previously stated, with the view that this pump could not be simply modified to "inline" as this would only provided us with a single option for barb size. This was due in part to the small surface area of the pump and the availability of barb sizes which would physically fit into this area. Simply put we could achieve some of our objectives by in line modification but this was not going to be sufficient for our needs. What we did come up with was this the prototype "Potted Eheim".

Fitted with 1/2" barbs

Fitted with 3/8" barbs

Fitted with 10 mm Compression Fittings

There would appear to be no reason why even smaller 1/4" compression fittings could not be used with this pump.

Filling

One issue with pump management that is really problematic is keeping the reservoir filled in those first vital seconds when filling the cooling system for the first time. Lets face it the liquid is there to cool the pump bearings...no liquid...no bearings and a dead pump. Simple really. You would be surprised at the number of emails we get from people who have burnt out their 12 volt pump this way and are looking for an Eheim to replace it. Eheim's will run for a limited period dry..............limited means that they will not run dry for long. They are, however, far more forgiving of abuse than their 12 volt counterparts.

To avoid this issue of running dry and potentially risking killing the pump we looked at a number of very sensible and simple alternatives. Rather than constructing one of those useless top fill seals to the pump enclosure we decided to add another tapped thread barb fitting point to accomplish the filling process. Now it is easy to install a barb into the threaded hole provided and with a funnel attached to a small piece of tubing the reservoir can be kept topped up during the early stages of the filling process.

When filling is completed the barb can be removed and the top seal can be replaced.

Performance

Before we go on to look at performance it may be relevant to add a timely warning and review a rather interesting feature of the Eheim Compact range of pumps. The Eheim Compact pumps have an inbuilt sliding flow regulator built into the bottom housing of the pump head. This is shown in the picture below as the light gray colored plastic part.

No doubt this was originally put there for aquarium use. If you purchase one of these pumps be aware of the feature or you can be left wondering what happened to all of your flow rate and head.

Next............................Performance and flow rate