Plumbing & Pipes for your Pond
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Before we talk about pumps, we feel it’s important to discuss the plumbing of a pond, since the choices made in the plumbing design will definitely affect the size of pump you’ll need. Some people skip this step of the pond design process thinking it doesn’t matter that much. While it’s definitely possible to slack on the plumbing design and still have a functional pond, the pond will likely be less efficient. As we’ll see in an example later, poor energy efficiency in a pond can lead to significant operational costs over the long term for the pond owner. With rising energy costs, we think it’s worth the time to put a little extra thought into proper plumbing and pipe design to help make the pond more efficient and streamlined.
What do we mean by plumbing?
When we say “plumbing” we are mainly referring to the pipes in a pond that carries the water from the pump to the filter, and then back to the pond. Sometimes when people refer to the “plumbing system,” they are talking about the pump as well. However, in this section, we’ll mainly discuss the choosing and placement of pipe for maximum efficiency.
Types of Pipe
There are two types of pipe we can use when plumbing an ecosystem pond: rigid PVC pipe and flexible PVC pipe. Like everything else in a pond, both have advantages and disadvantages. Let’s have a closer look:
Rigid PVC Pipe - advantages vs disadvantages
Most larger ponds or koi ponds will use either PVC or ABS rigid pipe rated for DWV (Drain, Waste & Vent). Schedule 40, which refers to a measurement of the thickness of the pipe wall, is the standard size for pond applications. PVC is the most common rigid pipe for ponds and is rated for pressure as well as DWV. ABS pipe is also rated for DWV, and while it is strong enough for pond applications, it isn’t usually rated for pressure. Some US states may not have ABS pipes readily available due to state specific building regulations. If ABS is available in your area, you’ll likely find it’s a little cheaper than PVC. In our opinion, PVC is a little better since the glue up area on fittings is a little larger, which helps when joining to flexible PVC pipe. In addition, PVC can be heated up and then bent to make sweeping bends and corners if desired. You can also connect PVC and ABS pipes together, as long as you make sure to use special glue called “transition glue.” Another trick we’ve discovered is that Schedule 40 PVC pipe from the electrical section will also work great in a pond. The benefit of electrical PVC is that it’s available in long sweeping sections that allow bends without sharp corners. For example, sweeps up to 60-degree corners are available in lengths from 1’ to 5’. As you’ll see later, the less abrupt a corner is, the more efficiently water will run through the corner, which in turn reduces the head pressure. The less head pressure, the smaller a pump you’ll need. We’ll delve more into head pressure soon.
Flexible PVC Pipe - advantages vs disadvantages
You might be wondering why someone would even consider using rigid PVC if flexible PVC is so much easier to use. Flexible PVC has some downsides that are more of an issue on large pond installs:
1) Extra friction.
With flexible PVC pipe, the walls are slightly ribbed to allow the pipe to bend. This means you’re going to end up with a little more friction in the pipe. Most people measure this to be around 5% to 10% less efficient than regular rigid PVC. More friction equals more resistance that the pump must overcome. For the main pipes and longer runs where you don’t really need the high flexibility, most contractors choose to use rigid. For our ecosystem pond, because the pipe runs aren’t that long, and we don’t have a lot of complicated filtration equipment like in a dedicated koi pond, we like flexible pipe. Although we will lose a little bit to friction using flexible pipe, for most ecosystem ponds it’s not really enough to worry about.
2) Flexible PVC isn’t as strong as rigid PVC.
If enough weight is put onto a flexible PVC pipe it can begin to “squish.” This is another reason many contractors still prefer to use rigid PVC—it can be buried with quite a bit of force on it and it’s not going to bend or break. In the past, flexible PVC pipe wasn’t good enough to run underground, which is why many people still don’t like it. However, the newer flexible PVC available can handle being buried with some weight on it, as long as the ground around the pipe is well compacted. It obviously still can’t handle as much weight as rigid PVC, but it’s enough for our ecosystem pond purposes.
3) Termites.
We have heard reports of termites eating through flexible PVC pipe in certain areas. If you believe you might have a termite problem where you live, you may want to consider rigid PVC instead, since the termites aren’t able to eat through the hard plastic as easily.
4) Flexible PVC needs PVC fittings (not ABS fittings).
This isn’t as much a disadvantage as just something to keep in mind. When choosing fittings to use with flexible PVC pipe, we find it’s better to use PVC pressure rated fittings rather than the ABS fittings mentioned earlier. The main reason is that schedule 40 PVC fittings are rated for pressure, and as a result have a larger gluing area. The ABS fittings have a smaller gluing area, which is fine for rigid pipe but is too small to get a good connection with flexible pipe.
Which pipe should I use then?
Even though flexible PVC has some downsides in certain situations, when used in the right place it can replace multiple rigid PVC or ABS fittings because of its high flexibility. As you’ll learn in the upcoming friction section, pipe fittings add resistance to the pumping system, so anytime you can avoid a fitting you’ll save on efficiency. Overall, for most DIY homeowners building an ecosystem pond, we recommend using flexible PVC because it’s so easy to use and install. Even in the worst case where a problem did pop up with the flexible pipe—say it got squished or kinked from too much weight, or a termite put a hole in the pipe —it wouldn’t be too hard to dig up the pipe and replace it down the road if necessary.
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