EHEIM Reservoir Mod

Water Cooling System

I really like the Eheim water pump, but I’ve had a difficult time with the intake metric fitting and threading. In my setup, a 90° angle 3/8″ return was needed to keep things simple for maximum space utilization.

My first brass fitting cracked the intake horn because of the MPT taper; Permatex Cold Weld was used to repair the crack and bond the fitting to the intake. This setup was closed loop without a reservoir and would run fine for approximately one month before air began to infiltrate the system. These problems prompted my quest for a cheap, space efficient reservoir.

A trip to the local Lowes store would supply the necessary PVC fittings, one 3/4″ street elbow, one 1″ x 1″ x 1/2″(threaded FPT) tee, and a 1″ bushing with 1/2″ FPT. Brass fittings include 1/2″ to 1/4″ bushing and 3/8″ elbow with 1/4″ MPT, and a 1/2″ brass plug. With glue all this cost about $5-$6.


I tested the cement on an old intake to see if it would activate the plastic and sure enough, it did. The street elbow required some sanding to fit the intake horn and aligning the parts is critical. My suggestion is to dry fit all components and place in the proposed mounting location prior to cementing because there is no going back without a new cover from Hawaiian Marine Imports (1-800-99-EHEIM). New cover are cheap BTW – about $4.

Filling and bleeding are much easier than the way I used to do it (submerging the entire pump in cooling fluid containing RedLine, not much fun). Trapped air is removed quickly. Also check out the Molex connector in the pump cord – makes removing the entire cooling system in one piece manageable (soon a relay will control the pump and will connect through that point).

I ran into one problem with the 1″ tee that wasn’t present with the 3/4″ tee version; the return jet can cause a whirlpool strong enough to suck air down into the intake.

I used plastic screen running around the inside diameter of the tee to break up the return flow but other means could be employed to do the same. Also, I cut off some length from the street elbow so the tee mounts as close as possible to the pump, and cut some length from the 1″ bushing to increase the internal volume of the reservoir.

The tee could be shortened to reduce overall height, not needed in my case. The 1″ setup holds about 3oz fluid.

Paul Glosser

Be the first to comment

Leave a Reply