A very common question we get asked is, "What are the differences between aerator class pumps and reversible pumps?" More often the question is actually phrased more along the lines of "Which type of pumps is better". This article will outline the pros and cons of each type of pump, as well as some potential applications to help you decide which one is best for your application.
Aerator Ballast PumpsFirst off, let's take a look at aerator class pumps. These pumps can also be referred to as Livewell or cartridge type pumps. Fundamentally, the most important thing to know about an aerator class pump is that they only run in one direction, so to fill and drain a ballast location will require the use of two separate pumps, one for the fill side and one for the drain side.
The other thing to be aware of when it comes to aerator class pumps is that they are not a self priming pump, which means that they're not capable of pulling water into where the pump is; they can only push water out from where the pump is located. That means there are more constraints regarding the placement of aerator pumps within the ballast system to ensure that everything functions correctly.
As long as those constraints are met though, aerator pumps are a very reliable option because of the fact that they have a rigid impeller which doesn't contact the walls of the housing of the pump. As a result, the pump is not susceptible to run dry damage, is incredibly durable and they're also quite inexpensive for the amount of speed that they provide.
One thing to note when it comes to real world applications of aerator pumps is that typically the rated capacity of the pump will be substantially higher than the real world capacity of the pump. When we add in things like back pressure from the additional fittings in the system and the amount of work that the pump will have to do to overcome gravity to lift the water to the top of the ballast bag.
In an aerator pump based ballast system, typically the fill pump will be mounted directly at the intake from the water source and will connect to the top of the bag, so it fills through the top of the bag while the drain pump would be mounted directly to the bottom of the ballast bag and will drain through a thru-hull connector on the side of the boat. Additionally, you'll need a separate vent overflow connection, leaving you with three total connections to the ballast bag and the accompanying hose and fittings necessary to support those connections.
Reversible Ballast PumpsFlexible vane impeller pumps, on the other hand, which are also known as positive displacement pumps or reversible pumps, are a pump that can be run in two directions by simply switching the current, the direction of the current going to the pump. So if you provide positive on one wire and negative on the other wire, the pump will run in one direction and if you reverse that, the pump run in the opposite direction.
This gives you the advantage of being able to both fill and drain with a single pump, reducing the number of components in the system. Reversible ballast pumps are also self priming, which means that they're able to pull water into the pump; picture using a straw to lift fluid up out of the cup into your mouth. Reversible ballast pumps can do the same thing which gives you much more flexibility in terms of placement of the pump within the boat and some added flexibility when it comes to potentially filling and draining more than one bag with a single pump, which can be done with a reversible pump but cannot be done with aerator pumps.
The downside though for reversible pumps are that they are more expensive upfront, although that cost difference is mitigated by the reduction in the number of components that are required in terms of hose clamps and other hardware and that they, because of the positive displacement nature of the impeller and the fact that it is a wear item that's contacting all sides of the pump housing, they're susceptible to run dry damage if not protected by use of something like our Ballast Timer Module and the impeller is a wear item that will have to be replaced at some point. Lifespan depends on usage, we typically suggest customers swap that out every one to two years.
Because reversible pumps both fill and drain, we only needed to make a single connection to the bottom of the ballast bag to service that bag. A secondary connection on the top of the bag is used as the vent overflow connection that is attached to the thru-hull connector on the side of the boat, which means only two connections are needed in a ballast system that uses a reversible ballast pump.
When it comes to installing a ballast system, the first decision to make is which type of ballast pump you plan on using. This decision will impact the rest of the system design and layout, as well as the number of components required for proper functionality. There are pros and cons to each type of pump, which we have summarized in the following table:
|Pros||Reversible, acts as a check valve, self-priming, fewer components in system||Affordable, durable, compact|
|Cons||Cost more, need run dry protection, limitations to pump placement.||Two pumps required, installation limitations, require additional check valves|
|Example||Jabsco Ballast Puppy, Johnson Ultra Ballast Pump||Attwood T800, Attwood T1200|
So there's a quick overview of the differences, pros and cons between reversible ballast pumps and aerator class pumps. If you have any additional questions, feel free to contact a product expert by email firstname.lastname@example.org, phone at (888) 338-6085, or by using our live chat feature.