Anyone help with water feature problems

[ged.clink]

Installed a water feature for the missus. It's essentially a 2 foot high gargoyle that spits water out of its mouth into a sunken pool ( covered with wire grid and stones). The water is then recirculated via the pump, up into the base of the gargoyle then back out of its mouth.

We saw the same set up in a local stockist and the gargoyle was sitting on the ground, throwing water out about 14 inches from its mouth. We wanted it to sit higher so the stockist ( who casts all their own products from concrete ) threw together a large upturned planter made of concrete and sat the gargoyle on it. Turns out he had never done this before i,e sat it up higher so it was a bit of trial and error for him

Connected it all up. Put the 12v pump into the plastic pond and turned on. Water came out about 3 inches then started to drop. It barely cleared the planter base and just made it into the pool. Given the plastic bucket is about 14 inches by 30 inches and the gargoyle sits at the end of it, I was looking for a throw of around 15 to 20 inches to hit the middle of the pool.

So back to the shop and he gave us a 750 litre and hour pump..We originally had been given a 650 lph. No difference.

Upto a 1500 lph.. No noticeable difference

Now onto a 2000 lph and it still just about makes the pond but not by much!! The shop owner is stumped...The plastic pipe going from the pump to the gargoyle is about 12 mm diameter. The connector coming out of the pump is about 20 mm diameter so I have used lots of gaffer tape to make up the difference. No leaks there.

The gargoyle has what looks like thinwall copper pipe inside the cement casting - placed in there before pouring. It looks like old microbore copper pipe for central heating.

If I take the pipe directly from the pump and hold it beside the gargoyles exit hole ( 1.2 metres above the pump ) it lands just about where I wanted it. Stick it into the gargoyles base and it falls short by about 10 to 12 inches??

Given this pump is meant to be shifting about 2000 lph then is it to do with the diameter of the plastic piping and diameter of tube inside the gargoyle that is creating the restriction?? Any ideas why I have noticed almost zero difference between a 650 lph pump and a 2000 lph pump??

I have worked around this temporarily by squeezing the copper tube at the exit point with pliers and this has the effect of firing a thinner stream of water into the correct part of the pond but it just isn't perfect.

Any clues or tips?

Thanks

Ged

[The3rd Earl Of Derby]

Yes the Microbore piping in the Gargoyle. :-)

-- Sir Benjamin Middlethwaite

[Clive Dive]

I feel your gargoyle is in need of an enema [orally administered]. try one of those 'net curtain wire' things and give it a good 'Barrymore-ing' ;-)

[david lang]

Hi Ged

Therein lies the problem. Impeller pumps loose flow when the pipe diameter is restricted. I reckon if the microbore pipe were the same size as the rest of the pipework all would be OK.

Dave

[meow2222]

What you need is not more flow but more pressure. Probably the output pressures of all your pumps are close to the same.

The usual type of water pump actually loses pressure when flow is reduced, so the bigger pump will be more compromised re outlet pressure.

The feature simply needs more pressure to get through its small piping with adequate flow.

One way to achieve this is to put 2 pumps in series, this will double the pressure. Work out what flow rate you need and no need to exceed this on pump rating. To do this, get the thing flowing as you want by any means, and use a bucket to measure the output per minute, and calculate accordingly.

A pump flow spec on its own means little, as it only applies when there is nothing on the pump outlet, no back pressure. This will not usually be reached IRL. What is more useful is a flow vs head graph.

NT

[Harry Bloomfield]

[e-mail] submitted this idea :

The higher you try to pump, the lower the flow rate.

Are you also uprating the 12v tranformer to match the larger pump?

If all the pumps provide similar pressure, then they will produce the similar output if the pipe sizes are similar. You would only see improvements if the first pumps output (lph) was not adequate.

Check the copper pipe is clear of obstructions, any restriction in the pipe will reduce the 'throw'. Also make sure the narrowest part of the system is at the output (the mouth), where it needs to build up pressure to produce the speed of flow to 'throw' the water.

[The3rd Earl Of Derby]

[e-mail] wrote: [snip]

Total ballcocks, he needs to widen the pipe in the gargoyle somehow.

-- Sir Benjamin Middlethwaite

[DJC]

The varous pumps are only improving the flow, what you need is higher pressure. You could try raising the pump so the flow from the pump isn't uphill.

[Set Square]

That would certainly help - but the comments made about pressure are *also* true.

This type of pump has a performance curve which starts at a finite maximum pressure at zero flow and ends at a finite maximum flow at zero pressure. The *actual* operating point for a specific application is somewhere in the middle - depending on the height to which the water is to be lifted and the flow resistance presented by the pipework.

The max pressure determines the max height to which you can lift the water - for it to just dribble out. It sounds as if the elevated gargoyle is using most of the available pressure to raise the water to nozzle height - leaving very little in reserve to induce a decent flow rate.

As someone else has suggested, putting two pumps in series may well be the answer.

[Set Square]

Unless he raises the basin from which the pump gets its water, that will achieve nothing - the pump still has to lift the water through the same vertical distance.

[meow2222]

If a pump is lifted above the water its pumping, it will airlock sooner or later. Including whenever its switched off. Only self priming pumps should be used this way.

NT

[meow2222]

It would help if its possible, I just assumed it would be impossible. But even then it may not make much difference, all depends what the main obstacle is, the narrow pipe or the extra height. Since the gargoyle is most likely designed to run on standard pond pumps, and does happily at its intended height, I would say the problem is mostly the extra height and the lack of thereby needed extra pressure.

NT