do pumps get weaker over time?

[sam75]

Do submersable pumps (ones with a magnetic impeller) get weaker over time? I know they need to be cleaned occasionally, but does the impeller become demagnetized/wear down eventually? Seems like several of my pumps are not near as strong as they used to be.

[jason the filter freak]

Do submersable pumps (ones with a magnetic impeller) get weaker over time? I know they need to be cleaned occasionally, but does the impeller become demagnetized/wear down eventually? Seems like several of my pumps are not near as strong as they used to be.

Simple answer is yes of course.

[Chad]

^I concur, and if I were to list the causes it would be in this order: 1) increased hydraulic friction caused by internal fouling of surfaces with organic mung, 2) increased tolerances between parts caused by wearing down of various surfaces (impellors, shafts, etc. 3) a decrease in the magnetic field doesnt really strike me as an issue unless overheating becomes chronic and insulation breaks down.

[Integral9]

If you have had the pumps running for a while (years if not a decade or more) I believe this can happen.

 

eg: Ever magnetize a paper clip, then use it (w/out the magnet) to pick up other paper clips? How long does that last? Granted these are weaker magnetic fields, but the principle is the same.

 

In the paper clip, the magnet causes the molecules in the paper clip to temporarily realign to produce their own magnetic field. However, due to most of the molecules not being aligned, this falls apart quickly.

 

In the pump, the electromagnet turns the ferrous magnet by reversing the magnetic field over and over again. This has the opposite effect of the paper clip and instead of the molecules in the magnet being realigned to produce a field, the opposite field from the electromagnet pushes the molecules out of alignment. Depending on the field strength of the two magnets, this takes a very long to time to happen as most of the molecules in the magnet are already aligned to produce the magnetic field and this helps to hold them in place and resist demagnetization. However, given enough time, all magnets will demagnetize on their own, but probably not in our life times. However, if the pumps have ever run dry or overheated, this can happen much faster as the additional heat will allow the molecules in the magnet to be realigned easier.

 

If you want to be scientific about it, you should be able to measure the magnetic field strength of the magnets with a volt-meter (multi-meter) by measuring the induced voltage from the magnetic fields across a piece of wire. Then compare that to the reading you get from a new magnet off a new impeller.

[Glenn]

Seems like several of my pumps are not near as strong as they used to be.

 

You don't actually state it but I'm guessing that you mean the waterflow from the pump to the display-tank is not near as strong. While the pump will definitely have a lot to do with this, don't forget that "stuff" will also be accumulating in your pipe/flexible hose and that will also decrease the waterflow.

[sam75]

Thanks for the response everyone. So I guess the question is do you (or is it common to) replace impellers after x number of months/years or only when they break? This goes for fan type pumps as well such as koralia's and vortech's. I guess what I'm wondering is what percentage of flow is lost after a 2 or 3 year period (provided it's significant enough to make a difference)?

[Integral9]

I replace mine when the flow slows down or when they break. I don't have a set schedule for replacement. I do clean them about once a month though.