VEGEPOD The best veges you will ever grow

Vegepod Raised Garden Bed Kits give you the best of both worlds and more. You get the size of a raised garden bed with all the benefits of container gardening. Not only that, you also get the benefit of an Raised Garden Bed Cover that extends growing seasons and accelerates plant growth.

Garden maintenance is minimal and watering is only required during the early stages of plant growth. Vegepod Raised Garden Bed Kits are simply the easiest way to grow your own vegetables.

Available now in store.

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Pipe Sizing - Fact or Friction?

What size pipe should I use? What do the stripes mean? Does a smaller pipe give me more pressure?

What is pipe friction? 

So many questions! And so many myths, rules of thumb, misinformation and confusion. Let’s go through it step by step and lay out the facts.

Pipe types.

I’m going to keep it simple and just talk about polyethylene (poly) pipe. But the principles are the same for PVC pipe, steel pipe, garden hose and all types of pipe. The main types of poly pipe are

Low Density, Rural and Metric. Common sizes for Low Density pipe are 13, 19 and 25mm. It is generally rated at 40-50psi. Low density pipe does not normally have a stripe.

Rural poly pipe is an old standard which remains popular with farmers and irrigators. It is often referred to as B Class poly and generally has a green  stripe. Rural pipe sizes are 3/4”, 1”, 1 1/4”, 1 1/2” and 2”. It is rated to 800kpa (115psi).

There are several classes within the Metric pipe range each with a different pressure rating and wall thickness. It is often required for domestic plumbing with a mains supply. Metric pipe ranges from 16mm up to 110mm and beyond (16, 25, 32, 40, 50, 63, 75, 90 and 110mm) and have a blue stripe. They typically have pressure ratings of 800kpa up to 1600kPa (PN8, PN10, PN12.5, PN16).

Pipe Sizes.

Thist can get confusing. The nominal size has little resemblance to the actual measured size. Also, Low Density and Rural poly pipe are measured by their inside diameter, while Metric poly is measured by the outside diameter.  For example, 1” Rural poly pipe has an OD of 29mm and an ID of 24mm, while 25mm PN12.5 Metric pipe has an OD of 25mm and an ID of 20mm. If you aren’t sure cut a small piece and bring it in.

Friction.

Here is where it all comes together. Friction is the resistance that a pipe imparts on water as it moves through. It’s a bit like putting your hand out the window of your car. When you are stopped there is no resistance, but the faster you go, the more resistance there is. It is also similar to voltage drop in an electrical cable. In essence the faster water moves through the pipe, the more resistance there is. The resistance is called pressure loss or pipe friction. For example, if we are moving 100L per minute through both a 2” pipe and a 3/4” pipe, the water will be moving faster in the 3/4” pipe - and hence there will be more pressure loss (friction) in the 3/4” pipe. Additionally, it makes sence that water flows quicker through a 1m hose than a 1000m hose. Friction works on a per meter basis. So, the smaller the pipe  and the longer the pipe, the more friction (and thus less flow) will result. We have charts and software to help work through this, so feel free to come in and get the right pipe first time.

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Twin Impeller or Single Impeller Firefighter?

This is possibly the single most misinformed subject that we come across in our business(apart from the one where a smaller pipe gives more pressure). So often we have customers coming to us with the intent of buying a twin impeller firefighting pump. When we ask why, the answer is always "Because you get more water don't you."

Don't you?

Well, maybe you do. And maybe you don't. Ask yourself this: Is a 4WD faster than a 2WD? It certainly is up a muddy steep climb or through a boghole. But probably not for a trip to town.

So let's take a closer look. What is an impeller? What does the twin impeller do?

Impellers are the spinny thing at the heart of your pump. As it spins it draws water into its centre and throws it out through its vanes, creating both pressure and flow. They come in lots of different diameters and widths and can spin at different rates. The diameter of an impeller will affect the pressure while the thickness will affect the flow rate. Extra impellers, in series, add pressure to each other, but do not increase the flow rate (in fact the flow rate decreases). So a twin impeller pump will deliver higher pressure but lower flow.

So, which pump do you need?

Take a look at the pump curves below. The single impeller pump delivers better flow rates below 40m of total dynamic head, while the twin impeller delivers more above 40m. So for general purpose pumping a single impeller pump will generally suffice. However for high pressure situations the twin impeller pump will be the best choice. Don't forget the pipe friction. In some situations the pipe friction will add up so that the total dynamic head is greater than 40m.

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