Water Pumps - Selection Guide.
Q. Why are there so many pumps choices?
A. Most pumps are specifically designed to perform a certain task. For example, a filter pump is designed to move solid waste to a pond filter, so this type of pump has large holes in the outer casing to allow the particles to pass through. A filter pump is therefore no good for use as a fountain pump, as any large particles would end up blocking the fountain nozzle attachment.
In the same way, a fountain pump shouldn't be connected to a pond filter, as the muck on the pond floor will simply get trapped around the fountain pump casing, rather than passing up to the pond filter - we receive a number of calls from people with clean filters, but dirty ponds - the wrong pump is usually the reason why!
Q. Fountain displays - which pump and what do i need?
Step 1. Measure the pond or the water reservoir length, width and depth. A fountain shouldn't go higher than half the narrowest point (for example, if your pond measures 5m x 3m, the fountain display shouldn't go any higher than 1.5 metres (half of 3m). The reason is to prevent water splashing outside of the pond on a reasonably windy day, if left unattended.
Step 2. Decide on the type of fountain display pattern. You can view a wide variety of Fountain Nozzles here.
Step 3. Click on the Fountain Nozzle picture and you will notice that we have already calculated the right fountain pump to suit the required display height. Simply click on the fountain pump for more details and pricing.
Q. Do you offer cheaper alternatives to the Oase Fountain pumps?
We do offer a cost effective range of pumps which can be used with our fountain nozzles. These can be viewed on the Watercourse and Cascade pumps page here. We tend to offer Oase equipment wherever possible, as this is the very best brand on the market, carrying long guarantees and offer reliable, consistant performance.
Q. Pond Filtration - which pump do i need?
Filter Pumps, also referred to as Solids-handling pumps, are purpose-build to force muck and debris from the pond, up to the filter. Debris is allowed to pass through the shell of the pump and the rotating impeller then forces this to the filter.
1. First, measure the pond Length, Width and Depth in metres. For this example, let's assume the pond measures L5m x W3m x D1m.
2. Convert the pond size into water volume by using the following calculation:
Length (in Metres) x Width (in Metres) x Depth (in Metres) x 1000 = Water Volume (in Litres).
In this example, the pond volume is: 5m x 3m x 1m x 1000 = 15,000 Litres.
3. As a rough guide, you should aim to circulate the entire pond volume once every 2 hours. This really depends on the type of pond filter used and also if the pond is purely ornamental or being used to stock fish or Koi Carp. In our pond example, the pump will therefore need to turn over around 7500 Litres per hour.
4. If you have already purchased a pond filter, then the manufacturer may state the maximum flow rate that the filter can handle. If this is the case, then it is important not to exceed this flow rate stated, as it may cause the filter box to flood over.
5. If you also need a filter, we recommend viewing our Pressurised Pond Filter Sets and our Gravity Pond Filter Sets. These filter kits include the water pump, filter box and UV Clarifier. We have already calculated which filter kit is required for specific pond sizes and we also account for fish stocking levels, so hopefully this will help in selecting the right choice of pump and filter for your pond.
6. Pump hose selection. Always try to use the largest diameter flexible hose to connect between the pond pump and filter. This is very important as when water is forced through a hose or pipe, it will generate friction. This friction, or resistance to water flow, will reduce the amount of water finally exiting the hose. The smaller the hose diameter and the greater the flow rate, the more friction created. This is a very important consideration and is often overlooked by many suppliers or is simply not understood.
Again, we receive numerous enquiries from people who have been poorly informed of correct hose selection, leading to wildly overspecified pumps (meaning high running costs) or poor pump and filter performance, simply because of the hose being too small for the task. For more details on calculating friction loss, please see the next section below.
Confused? Call on 02392 373735 and we'll do our best to help.
Q. Waterfalls, Streams, Cascades and Watercourses - which pump do i need?
The calculations used for pump flow rates on Streams (Watercourses) and Cascades (waterfalls) are virtually the same.
1. Firstly, measure the width of the stream at its widest point (i.e. how wide the water channel will be). For this example, let's assume this is 0.6 metres wide.
2. Measure how high the top of the stream is, above the pond or reservoir water surface level (not the bottom of the pond). Let's assume this is 1.5 metres.
3. Next, measure how long the flexible hose will be, from the submersed pump to where the water will exit at the top of the stream (the 'point of discharge'). It is better to over-estimate the hose length. Let's assume the hose measures 10 metres in length.
4. As a guide, you will need approximately 1000 Litres/Hour for every 10cm of stream width. In our example, the stream measures 60cm wide, so we need 6000 Litres per hour at the point of discharge. This will produce a gentle stream of water - if you require a more dramatic display, we suggest doubling or trebling this figure.
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5. Next, we need to calculate the friction losses through the hose. Let's stick with 6000 Litres/Hour (roughly 100 Litres/Minute) down the stream.
Take a look at the chart to the right. Let's compare the difference between using a 25mm (1")Internal diameter flexible hose and a 40mm (1 1/2") hose.
On the 25mm - 1" section of the chart, we need to look at the '100 Litres/Min' line. You will notice that the chart reads '0.34MWC. This essentially means that for every metre of flexible hose used, it is the equivalent of pumping uphill by 0.34m. As we have 10 metres of hose, this equates to a 'loss' of 3.4m.
Now, let's compare by using 40mm - 1 1/2" Hose at 100L/minute.
0.03MWC x 10 metres of hose = 0.3m loss. |
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6. Based on the friction losses, we can now look at selecting the most suitable pump. In this instance, let's use the 'performance curve' from the Oase Aquamax ECO pumps.
If we choose the 40mm - 1 1/2" Hose, we simply add the actual vertical lift (1.5m) to the Friction Loss (0.3m) = 1.8m total vertical lift. We need therefore need 100L/Min @ 1.8m Height so follow the vertical line at the bottom of the chart upwards until you reach 1.8m. You will notice that this falls between the Aquamax ECO 8000 & Aquamax ECO 12000 pumps.
Based on this, we would recommend the more powerful Aquamax ECO 12000 Pump, giving you a little more (rather than too little) flow, matched with 10 metres of 40mm (1 1/2") flexible hose.
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NOTE: If you now compare the 1" hose (1.5m actual lift + 3.4m Friction Loss = 4.9 metres total lift), NONE of the Aquamax ECO pumps are powerful enough!
This highlights the importance of selecting the biggest hose that the pump connection will allow, to get the very best performance from the pump. If 1" hose had been selected, the pump would need to be far more powerful initially, to combat the massive frictional resistance in the hose. |
Confused? Call on 02392 373735 and we'll do the head-scratching for you!.
