Friday, March 29, 2019

Repairing And Maintaining A Cast Iron Water Pump

For all the readers who have asked, this is a primer on basic repair and maintenance for a cast iron water pump on a preschool playground.

We've had a cast iron water pump around the school for the better part of two decades, but only as a "permanent" installation for the past ten years. I use quotes around the word permanent because ours is actually mounted on a piece of wood that we sit over a large plastic tub that acts as our cistern. Perhaps a less transient arrangement would be more aesthetically pleasing, but the advantage is that it makes it far easier to service and repair. And if you're going to have a cast iron water pump on a preschool playground, it will require occasional, if not frequent, maintenance. It's worth the effort given that our pump is probably the single most used item on our playground, year-after-year, but it's important to know what you're getting into.

The biggest challenge is that debris like sand, wood chips, pebbles, and small toys find their way into the top of the pump. By this point in the year, even most of the two-year-olds have internalized our mantra, "If you put things in the top of the pump, it will probably stop working," but whether done intentionally or inadvertently, it still happens.

When the pump stops drawing properly, I lift the pump from the plastic tub and carry it, wooden platform, intake pipe and all, down to the workbench. I almost always do this when their are children around to watch and they tend to follow me down the hill and gather around asking questions. I carrying on a running commentary about what I'm doing and why for their benefit. I mention this by way of apologizing for the blurriness of a couple of these photos: I was being jostled by the crowd as I took them.

The only tool you need is a wrench. I usually start by removing the top of the pump which is held on by a single bolt located under the pump handle.

I loosen the bolt, then lift the handle, top, and plunger off all in one piece. 

I examine the plunger for any debris.

More often than not, I'll find that the culprit is a wood chip that is trapped between the plunger weight and the plunger cage. Here's a picture of what I'm talking about. This is the "cage" with the weight in its center . . .

. . . Here I'm using my finger to lift the weight to show you what I'm talking about. If debris is trapped between the weight and the cage, the pump won't work effectively. Usually, all I have to do at this point is to remove whatever is stuck in there and put the pump back together. And while we're looking at this picture, I want to mention that the brown part my thumb is touching is called a "cup leather." Under normal use, manufacturers say that these need to be replaced once every 5-7 years. Under our playground use, we're replacing it at least once, sometimes twice a year. It's a simple process of unscrewing the large threaded nut at the bottom, pulling off the old leather, and replacing it with the new one.

Sometimes, however, the problem is at the bottom of the cylinder.

This might require removing it from it's base. To do this, you just loosen or remove the two bolts holding it together. There is one on both sides.

This will allow you to access what is called the base valve, but what I call the "flapper part." 

I call it that because it opens to allow water to be sucked up into the cylinder and closes to hold water in, flapping up and down as kids pump. Often debris will be trapped under the flapper. And again, while we're looking at these photos, I'll point out the brown part, which is piece called the "flat leather." We replace this as well once or twice a year, usually when we replace the cup leather. One need simply remove a bolt, take off the old leather, and screw on a new one.

Finally, I always check the inside of the uptake pipe (the pipe that goes down into the water in the cistern, to make sure there is no blockage. It's rare, but every now and then something get sucked up into it.

While I have the whole thing in pieces, I like to rub a nice glob of faucet grease inside the cylinder to make things work more smoothly, although it isn't necessary. I then reassemble the pump and carry it back to it's cistern. Sometimes you'll need to pour a little water into the top as you pump to get it drawing water again: this is called priming the pump.

If you have a cast iron pump or are considering one, you'll need to know how to maintain it or it will spend most of it's life as a useless relic. Like I said, however, it's completely worth it and after you've done it a few times, it will seem simpler that perhaps it does in this little primer.

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