Will Swimming Pool Pumps make good garden pond pumps?

Selecting garden pond pumps for my backyard

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I found two potential pond pumps while searching for recycled items for my DIY Backyard water feature. These pumps were previously used for a swimming pool and came with one sand filter and one cartridge filter. This leaves me with the questions

Do the pumps have characteristics that I can use?
Are the filters of any use to me? If not I will 'freecycle' them again.

Both these pumps are not submersible and therefore cannot be hidden at the bottom of my garden pond or recovery drain pit and they'll need some protective housing.

I plan to use pond pumps to return water from the lowest part of my garden to the water tank and to supply sufficient pressure to operate my waterfall and/or fountain. The key characteristics to consider in this situation are flow rates, head of water (how far does the water need to be lifted vertically), noise and duty cycle.

Pump manufacturers usually supply graphs with pump performance curves showing head vs flow. As I don't have operating manuals for these old pumps (and they're not available online) I've looked at their specification plates and noted their rated power in watts and speed in rpm.

These are:

Pump 1 (Model 4145) 550w 2800 rpm

Pump 2 (Filtrate) 360w 2750 rpm

Next I've looked at a catalogue of OASE pond pumps that I picked up at a local water garden center and found filter pumps with similar characteristics. I measured the maximum vertical height from my water collection point to my storage tank inlet at 2.6 meters. By locating the point on the curve in the catalogue that corresponds to 2.6 meters I see that the smaller pump can deliver a flow of 120 liters/ minute. Keeping in mind that my water storage tank only has a capacity of 250 liters I should be able to refill it in 2 minutes.

To verify that my ex-swimming pool pumps can actually perform as pond pumps with this flow I have decided to test them by buying and attaching a hose with the same diameter as the pump outlet and seeing what sort of flow I get after lifting the loose end 2.6 meters!

I get 'Expert' advice.

Today I visited a water garden supplies retailer to seek advice on some of my water feature plans. I discussed some of them with their consultant who had worked in the industry for many years.

His reaction to my intention to use recycled swimming pool pumps as pond pumps? "You can't use them!"

Me - "Why not?"

Expert - "Well for starters they'll cost you an arm and a leg in electricity charges,[roughly a dollar a year for every watt of their rating - so if your swimming pool pump is rated at 1,200w then you'll be up for $1,200 a year, whereas a good purpose built pump will only use 400w meaning a saving of $800 per year]. Secondly swimming pool pumps aren't designed for continuous running. They are noisy so will not fit it with the tranquility you want from a "babbling brook" water feature. Also because they are not submersible you are going to need some sort of enclosure to hide and protect them - 'proper' pond pumps are not seen or heard".

Me - "But I'm not planning on running my waterfall continuously - only when I'm in my backyard."

Expert - You'll need to keep it flowing for the health of your fish and pond plants."

Now I don't plan to have fish but I do plan to have pond plants and I recognize I'll need to have some periods of water flow - but how much? - surely not continuously - further research needed!

I figure if I run my pond pumps for an hour a day to refill my water storage tanks and then allow a lesser flow from the waterfall to occur with gravity then this should suffice.

One possible scenario: Allow for 'trickle' flow for 8 hours per day (9am to 5pm when pumps wouldn't be heard by neighbors absent at their workplace) where trickle flow is 25% of pump flow. This would mean the pump would operate for a total of 2 hours per day which should be fine for my pumps designed to filter a swimming pool.

Unless my recovery pool (from where the water is pumped back) can store the same amount as the rainwater collection tank at the top of the garden (2 x 250 liters = 500 liters) then I will need the bottom pump to operate frequently to prevent the recovery pond from overflowing.

For example: If the pump has a flow rate of 50 liters a minute and the recovery pool has a capacity of 200 liters then the pump would empty the pool in 4 minutes. If the waterfall and stream have a flow rate of 12.5 litres per m inute then the bottom pond will fill in 16 minutes. This would mean a continuous cycle of 'pump on' for 4 minutes (less to prevent dry pumping) and 'pump off' for 16 minutes - 24 cycles every 8 hour operation. To regulate flow between no operation, trickle flow and gushing (for showing off to visitors) I'll use a faucet on the top storage tank.

If I do not have fish and can keep the water reasonably clean then I'll not need the swimming pool filters. I'll need to avoid disturbing silt with gushing water and diverting other ground water from my system. You'll find a more general discussion of how to select new pumps suitable for your water feature here.

To learn more about other water features for indoor and garden visit my home page.