All Pumped Up

Freshwater pumps require minimal care, but they sometimes need to be replaced. Here’s how.

One of the most common plumbing complaints boaters have is a badly behaving freshwater pump. Whether the problem is noise, a leak or “no water,” some cruisers believe pumps just suck. Fortunately, these pumps don’t require a lot of attention to keep them going, but the care they do require is important, and sometimes critical.

The most common pumps on recreational boats are the diaphragm style used for pressurizing freshwater and deck washdown systems. Most of them use an electric motor that drives a rotating eccentric cam or plate to actuate three or more neoprene-capped pump chambers. Each chamber is equipped with an inlet and outlet valve to ensure a positive, pressurized fl ow of water. The only maintenance that diaphragm pumps normally require is a regular cleaning of the strainer between the pump and the water supply. The task is important because tiny bits of foreign matter can lodge in a pump’s valves and cause them to leak, resulting in a loss of pressure and excess cycling of the pump. If your boat doesn’t have such a strainer, make it a priority to install one, but make sure the strainer’s flow rating matches the pump’s rating, to avoid restriction.

Another type of diaphragm pump has a single, large pump chamber whose diaphragm is operated by a crankshaft and connecting rod arrangement mounted above it. The crankshaft is powered by an electric motor that may drive it directly or by means of a miniature rubber belt. Single-chamber diaphragm pumps tend to have a high capacity and are often found on larger boats, but their inlets must still be effectively filtered. Rubber belts, if present, should be periodically checked for wear or damage. And an extra belt should be part of your spares kit.

Normal maintenance won’t always keep a pump operating effectively. That’s why most manufacturers offer inexpensive rebuild kits for their pumps. These kits contain all the replacement parts normally required to return the pump to its original performance.

Aboard Easy Goin’ we’ve elected to carry a spare water pump rather than a rebuild kit. For us it’s easier to replace the pump and take the failed pump home and rebuild it. Pulling a defective pump out and slipping in a new one isn’t a difficult task and takes less time than undertaking a rebuild.


On-the-Spot Replacement

First, figure out if the boat’s freshwater tank is higher, lower or on the same level as the water pump. Unless the tank is much lower than the pump, or it is equipped with a shut-off valve, you need to drain the tank so water doesn’t adhere to gravity’s call and rush into the boat.

With the pump’s master power switch turned off and all the water drained from the freshwater holding tank, it’s time to tackle the removal portion of the job. Disconnect the leads that run directly into the pump, which are typically red and black in color. Some have push-on connectors and others may use heat-shrink crimp connectors. Cut the wires as close to the connectors as possible.

Next, use a wrench or possibly “water pump pliers” (aka Channellock) to remove the waterline fittings from the pump. Have a towel or absorbent rag at hand, because there will likely be some amount of water in the lines that will drain out when the fittings are disconnected.

Water pumps are usually held in place either on a bulkhead or horizontal surface with three or four screws running through a rubber “foot” that absorbs vibration and cuts some of the noise. If the replacement pump’s footprint is identical to the old pump, there will be no need to drill any new holes for mounting. With the old pump out of the way, clean the area, clearing away any water and debris.

Replacing the old pump with the new one is basically a “reverse order” operation. However, give thought to the mounting screws that hold down the pump. In one instance I found the old pump screws had square heads. As much as I like using this style of screw, the pump was tucked back in a dark corner with little clearance. Since I couldn’t see the screws to appropriately line up the driver tip to get them out, there was a lot of grumbling frustration before I completed the task. When the new pump went in, I mounted it with Phillips head screws; it should be easier to remove, if there’s a next time.

In this same vein, don’t overdo it on the torque when you reattach the waterlines to the pump. Simply hand-tighten the fittings, then give them a little snugging with the wrench. Then, put some water in the tank, flip the switch and check for leaks. Tighten any fittings that leak only enough to get rid the leak. Overdo it and you may crack the plastic fitting.