Pumps II


Premium Member
Rex - I enjoyed reading part II of your article. I can't stress how important frictional losses are when picking out a pump for a return. So many people over look this critical step during the process and wonder why their return rate is so poor!

I would have spent more time on the subject myself. :d

I believe some comparisons would have helped you to bring your point across. Some people "understand" the point better when the data spelled out for them.

Also, frictional losses have their limits as well. There's a point of "diminished returns". Friction will always occur, no matter how smooth or how large the pipe diameter is.

I know most people use the "one size above your outlet" rule; this however really doesn't work in most cases. The velocity of the water being moved needs to be considered as well. Two sizes above the outlet usually works the best, again, not in all cases.
Your right of course concerning the importance of plumbing losses and I tried to stress the importance in part II of keeping the pumps flow velocity down to help control this (and will again in part III). And yes, other factors effect the pumps equivelent output head as well (e.g. number and type of turns, run lengths, etc.) but I did not want to get too technical and lose much of my intended audience so I mearly mentioned some of these in passing (I had to split the thing into three parts as it was).

I suspect your already aware of P. R. Escobal's book "Aquatic Systems Engineering" but if not and for others that might be interested in more detail in understanding and/or estimating their plumbing losses, this is the book to get (Dimensions Engineering Press, 1996, ~$30).

Your point on using larger diameter plumbing is also valid, though my personal preference and indicated as such in part III of this series is to split a pumps return into two or more lines which also reduces flow velocities (and thus effective pump losses) and additionally gives more flexibility in controlling circulation flow patterns in the tank through having more than one return.

If one uses his or her imagination there are all sorts of plumbing configurations you can come up with to improve both your circulations reliability as well as quality and I'll talk more about this in the next article, though by no means with this be meant to be more than an brief introduction to some of the possible configurations. My goal here is to get folks to start thinking more about some of these ideas/concepts and doing so hopefully come up with their own solutions to best fit their specific requirements.

Thanks again for the encouraging feedback, RN