Submersible Pump maintenance

Submersible Pump Types and Effective Submersible Pump Repair

Your pump represents a sizable investment in your water feature, so you may want to keep it alive as long as possible. There are a number of techniques to safeguard your pumps. Depending on the type of pump you have, some tips will be more critical than others, but all the techniques below will prolong the lives of any pump.

How to Perform a Submersible Pump Repair and Maintenance?

In order to successfully perform a submersible pump maintenance, it is important to know the different available drives, such as direct drives, mag drives or asynchronous hybrids. Always unplug the pump before the repair, and properly remove the blocking materials.

Types of Submersible Water Pumps

Direct Drives

submersible pump maintenance
Deposits Within the Pump

The first submersible pumps used for water gardens in this country, Direct Drives, were originally developed for sump and sewage duty, and are still a favorite of contractors for their strength and durability. These pumps are called Direct Drives because the impeller is directly connected to the electric motor via a shaft. The impeller has to be in the water, and the motor has to stay dry, so the shaft needs to have seals, usually two or three, that keep the water out of the motor. The seals have to work whether the motor is running or stopped, hot or cold, and the impellers are typically heavy, so the motor has to be strong enough to overcome the resistance of the seals and impeller, and that takes power, which costs money. Still, if you need a pump that can chop through algae, or can pump to very high heads, Direct Drives are the way to go.

These strong, durable pumps are a favorite of contractors because they withstand abuse and neglect pretty well, but there a couple of situations that will shorten their lives quickly. Most damaging are conditions that lead to overheating. Direct Drives in skimmers are especially vulnerable to overheating when the filter media, whether bags, mats or pads, are neglected. Left too long between cleanings, clogged media block the flow of water into the pump chamber; the water level around the pump drops. Air around the top of the pump removes heat 100 times less efficiently than water, and the pump starts to overheat. Most pumps are protected with a thermal switch that turns them off when they’re about to melt down, but the switches have a limited lifespan; after a certain number of cycles they fail, and that’s the end of the pump. This is the number one cause of skimmer-mounted pump failure.

Mag Drives

If you don’t need high head capacity, you can save operating costs by lightening the impeller and eliminating the seals, and that’s exactly what Magnetic Drive pumps do. Imagine taking a ‘doughnut’ of copper wire and ‘frosting’ it with a waterproof icing. If you suspend a magnet inside that doughnut and connect the coil to power, the magnet will spin, by magnetic induction. Attach an impeller to the magnet and presto! You have a Mag Drive. The pros are: there are no seals to deal with; energy consumption can be very modest and the simple impeller is easy to replace. On the other hand, Mag Drives don’t have the power to produce a lot of flow or head pressure, so they’re mainly useful in smaller ponds, under 500 gallons. One other quirk — that magnet that spins when the coil is energized? Well, you never know which direction it’s going to turn on startup, so the impeller has to be able to work in either direction.

These little pumps are almost maintenance-free. They are hard to overheat as long as they are kept submerged, and can run for years without failure — IF they are kept clean. Two things will kill them; one can be repaired, one can’t. The first situation is pretty common – a small piece of mulch or twig gets past the prefilter and jams the impeller. When the flow stops, most folks’ first impulse is to unplug and re-plug the pump, to free the impeller, but this can backfire and snap the ceramic shaft that the impeller spins on. Luckily, the shaft, impeller and magnet assembly can usually be replaced at a modest cost.

The second situation that’s especially damaging to Mag Drives is to have the pump sitting directly in the pond, down in silt or sediment. Constantly pumping abrasive grit can wear the bushings that the impeller shaft rides in. Once worn, the shaft will start to wobble and the Mag will start to fail. Usually, the bushings are difficult or impossible to replace, so that’s it for the pump.

If you can get the magnet to spin in only one direction, you can make a more efficient impeller and… enter the Asynchronous Hybrid Magnetic Drives.

Asynchronous Hybrids

By figuring out how to make the impeller spin in only one direction (so-called “asynchronous” rotation) you can combine the magnetic induction of the Mag Drives with the efficient, one-way impeller of the Direct Drives. The Asynchronous Hybrid Magnetic Drive pump combines the efficiency of the Mags with higher flows and head pressures of the Direct Drives, and have become the mainstay of the industry. ‘Asynchs’ excel at providing flows up to 6000 GPH, to heads up to 30 feet, at very low wattages compared to the other types of pumps. The catch this time? The high efficiency requires close tolerances inside these pumps, which makes them susceptible to clogging and scale buildup. They need to have good prefilters to keep debris out, and regular cleaning where lime scale and other water deposits are a problem.

The popularity of these pumps is well-deserved. They are quiet, powerful, efficient and can be long-lived, if a couple of precautions are taken. Their efficiency is gained through tight tolerances between the spinning rotor and the ‘can’ it sits in. Any debris or deposits that build up in the space between them will eventually cause the pump to fail, either by wearing off the stainless steel cladding surrounding the copper coils, or by cementing the rotor into the can. Deposits around the rotor are the single greatest cause of Hybrid pump failure. Luckily, there is a simple, effective way to avoid an early demise.

How to Maintain a Submersible Water Pump?

  1. Keep the Pump Under Water: Keep the bags, mats or pads in your skimmer clean, to keep your skimmer-mounted pump fully submerged at all times. Alternately, use a skimmer with brushes, which allow water to bypass between them when full of debris, keeping water flowing to the pump at all times.
  1. Make Sure that the Impeller Can Spin Freely: When flow stops, unplug the pump, check for blockage and make sure the impeller can spin freely BEFORE plugging the pump back in. Use a pencil or screwdriver to rotate the impeller one full turn. If it doesn’t turn freely, remove the impeller housing, find the debris and remove it. This goes for all pumps.
  1. Keep Sand out of the Pump: Either mount the pump in a skimmer, or keep any pump that’s sitting in a pond a few inches off the bottom, on a flat stone, to keep abrasive sand out of the pump.
  1. Clean the Pump Regularly: Open and inspect the pump after the first month of operation, especially in areas of hard water. If there is any evidence of hard water deposits, undiluted white vinegar should remove them with little effort. Check the pump again after another month to see if the pump will require monthly maintenance, or can go longer between cleanings. Although it does take some time and effort, regular cleaning will keep your Asynchronous Hybrid pump alive and well for years.

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