11 messages
12/10/2013 at 14:12

hello I'm creating a water feature in which I need a constant downward stream of water of relativley low pressure. I'm imagining I'll have a pump in the lower body of water pumping water up a pipe which then bends round to ermerge over the lower body of water , creating a cycle. This is actually for a multi-meida project so the water doesnt need to be filtered or anything I just need a pump that will pump a constant stream of water that is relativley cheap. the stream will be about the pressure of a tap turned to half power.

 

my question is , which pump do I buy ?

 

thanks , sam 

12/10/2013 at 14:27

Hello Sam, we made a similar feature with an imitation spring arising out of a rocky area. We buried an old black bin in the ground to provide the reservoir and then fitted a small pond pump onto a raft of wood that we fixed to the top of the bin. You don't need a lot of power, maybe only 350 to 400 litres per hour. Very cheap. Fix an adaptor at the plug end to cut out in the event of a power failure etc. You do have to top up the reservoir from time to time as the water evaporates/blows or splashes away.

12/10/2013 at 14:33

ah thanks watter butts , does it matter too much which pond pump ? I was worried that i'd buy one that had a pulseating flow by accident. I read up allot on pumps on engineers toolbox but it hasn't actually helped me pick one !

 

Also what was the emerging stream like , were making a kind of water harp so we want one thats qiute narrow and static , was yours like that ?

thanks , sam

12/10/2013 at 14:38

I'm afraid it's been buried so long I can hardly remember. It was a Hozelock one, I know that. Trouble free. It came with various attachments to make different types of spray shape. I think one was a fan shape, but we never used any of them. We just drilled a hole in a large stone with a masonry drill and put the hose through it. It just bubbles out of the "ground". No pulsation so far as I can tell. No noise either.

12/10/2013 at 14:48

ah thanks very much , I'll look inot that 

19/10/2013 at 18:57

Most pumps you will buy from a pond/water garden place will likely be a rotating impellor type (centrifugal), the water flows in to the centre of a rotating disc with vanes and is then squeezed through a chamber that is actually smaller than the inlet leaving at a tangent creating pressure. Some pumps will come with a fountain and waterfall attachment allowing you to pump water to another location whilst having a fountain close to the pump, you can sometimes vary the flow that goes to either the fountain or down the hose. This is great for what you want, you don't need to use the fountain attachment, but by opening or closing this valve it will change the amount of water going through your feature, the remainder will just be recirculated in the sump or pool or whatever you have feeding the feature.

Something like this might be okay, and at £35 ain't going to break the bank - http://www.worldofwater.co.uk/products/Hozelock-Cascade-700-Pond-Pump.html - one word of warning, remember that the greater the height difference between the pump and the outlet of your feature the lower the flow rate will be. Also, your pump has to be below the level of the main reservoir, you can not mount it next to the outlet, if this is above the water reservoir, pumps don't suck, well not this sort anyway.

rich

21/10/2013 at 13:10

cheers for the exhaustive reply , I was actually on the verge of ordering the one directly below that (the hozleock cascade 450). seeing As im gonna need my outlet to be about 0.65 meters above my main revoir and I want the pressure of the stream to be about 2bar do you think 450 litres perhour is enough. 

21/10/2013 at 18:40

I don't think you want the pressure of the water to be 2 bar, that is a lot, the 450 litre pump has a 1m head, this means that the pump can pump water up 1m, this is equivalent to 0.1bar. If you want to generate 2bar pressure you are looking at something considerably larger than a pond pump, you need something capable of pushing water 20m up a vertical pipe, bearing in mind of course that there will be no flow at 20m up, the pump impellor will literally be spinning in the pump pushing water out as fast as gravity is trying to pull it back down.

If the water feature is an open pipe then there is no pressure to speak of, you only generate pressure when you restrict flow. You need pressure to overcome gravity, to lift the water the height that you need and have sufficient energy left to give you flow.

http://www.hozelock.com/uploads/pdf/Aquatic%20data/Cascade/Cascade-performance.png

With the chart linked above, if you lift the outlet of the hose 1m above the pump then there is no flow on the 450 pump. If you mounted this pump level with a gallon bucket then it would take just under 1 minute to fill, the minute you lift the bucket it takes longer.

Think more about what you want the feature to look like and then work from there.

21/10/2013 at 22:44

I now know who to ask about water features 

22/10/2013 at 10:05

ah okay thanks , your right 2 bar is too high , the one thing that i'm a bit worried about is theres no description of the degredation to flow rate at different heights of under one meter. I think i will buy one and test it out. cheers

22/10/2013 at 19:21
Farmergeddun wrote (see)

I now know who to ask about water features 

Ask away, although probably best to message me, not always around. I am no expert on water features, but I did study Chemical Engineering for 4yrs and then spent 13 yrs working with systems to move, spray and control fluids, I can not claim to be an expert though.

sam hallett wrote (see)

ah okay thanks , your right 2 bar is too high , the one thing that i'm a bit worried about is theres no description of the degredation to flow rate at different heights of under one meter. I think i will buy one and test it out. cheers

I wouldn't worry too much about flow loss below 1m, if you have a pump that can deliver the flow you want at 1m  then you can always set up the system and then either restrict the flow by perhaps tightening a jubilee clip around the discharge hose or even make a number of small holes in the pipe close to the pump, the more holes the less will make it to the outlet at the water feature.

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