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Solar Water Features: What size solar pump should I get?

#1 · 14th January 2022, 2:32 pm

Hi, I've decided to install a 60cm granite sphere water feature in my garden, but I cannot find a definitive answer to what size solar pump I will need. The solar pumps run on litres per hour, but I suspect I will need a stronger solar pump than an equivalent electric pump. Does anyone have any experience or advice on this please?

#2 · 16th January 2022, 11:22 am

Hello Jini,

Your installing Granite Sphere which is 60cm, in old money this is 2 Foot, being an old codger I like feet and inches, I know pump capacities can be shown in litres per hour, but you also need to think about the pumps maximum height.

Let me explain, you have your Sphere, under that Sphere you will need a container for the water, lets go silly, if your sump or water container is 5Ft deep, the pump has got to push the water up from the bottom of that container 5Ft, and through the hole in your Sphere which is 2Ft, therefore your pump has got to be able push water upwards comfortably to a height of 7Ft.

I would suggest that you buy a pump that is bigger more powerful for height and litres per hour than your requirements, I am not talking about a pump being bigger in actual size, I am talking fountain height and Sphere size, the reason being, some pumps when purchased come with a Flow Valve already fitted, this means you can turn the valve down, as in turning your taps indoors down, water flow/pressure “Down” to your requirements. It is no good buying a pump that will struggle only giving you enough pressure to push your water up 4Ft high.

So check the size of the sump/water container your going to purchase, this for under your Sphere, if it’s 2Ft deep (60cm) add to this your Sphere height 2Ft (60cm) you get a total of 4Ft (120cm) you need a pump that will give you a minimum height of 4Ft, better to get a pump that gives you 6Ft and reduce the pressure, its then not running flat out, as you are buying a Sphere you only require the water to flow out of and down the Sphere’s sides, I presume not coming out of the Sphere looking like a fountain.

So look for a combination Litres per hour and most pump manufacturers will also give, fountain or head height, remember go a bit more powerful than required, you can always turn the power down, hope it goes well.

Bob

Lee Garden Ninja has reacted to this post.

#3 · 16th January 2022, 12:05 pm

Hi Jini,

Fantastic advice as always from Bob one of the Garden Ninja sensei members!

I've very little to ad other than always working out the height the water needs to be lifted and also the diameter of the hole which with some maths can allow you to work out the litres an hour the pump can move.

How to choose a solar water pumps size?

I always buy a bigger size pump than I need as you will find over time it slows down. Also, the rates that pumps are sold at are for clean water with no debris. In real life, your pump and pond/reservoir will contain all sorts of bits and detritus that the pond pump filter will capture. However, that increases the resistance for the pump so bare than it mind.

With a solar pump, I always find their listed litres per hour are also based on direct maximum sunlight which most gardens won't get.

In most cases I would always recommend a wired mains pump for consistency but if that's not a possibility just choose a larger solar pump than you think you need. I would advise for this they will be at least in the £120 bracket if not more as guidance. A solar panel that has a battery to retain charge is also worthwhile vs a solar pump that only pumps when the suns out. ie no storage capacity.