Overflow for a pond ? ... howto

[Rick Hughes]

I have been digging out to build a pond in garden ... it's around

600gall in size. It has filled and overflowed many times in past few months... so before I do the liner & edging need to consider a drain. Nearest drain is too far away to simply put in a gravity run .... would need to be pumped.

One thought is to create some form of sump, (plastic box) below ground level, arrange overflow pipe from pond - flow starts once water gets passed certain level.

Fit a float operated pump ... either a Hippo 2a

or maybe cheaper a bilgepump from a boat (I have 12V supply nearby) such as

Difficulty is how do I build in some form of hysteresis .. or it could be forever cycling pump. Wouldn't want a tiny amount overflow .. pump starts ... stops seconds later ... or do I have to just accept that. Tried the pond & garden groups .. they all rely on simply allowing overflow or have them built at a highpoint and a gravity drain.

Any ideas ?

[Owain]

Some form of tipping container that fills up slowly, then tips and dumps it all in the sump which is them pumped out.

Owain

[Toby]

The Hippo pump with the integrated float switch has hysteresis which is adjusted by the length of the cable you leave between the pump and the float.

I have a similar pump used to transfer water from a water butt over to some large storage tanks for rainwater - the water level needs to be about 6-8" above the pump to activate it, then it shuts off when there is bout 1" left in the barrel.

So if your bury your plastic box and link it to the pond at the top, it will gradually fill when the pnd is at max level, and then more water arrived, then the pump will purge the overflow box when it is nearly full.

If you use a short dip tube into the pond, and a longer one into the box (so an 'n' shape with a longer leg into the box) then the water should then fill up to the high point, and then create a siphon when there is heavier rain, to empty the pond to the level of the bottom of the pond side of the tube.

You will need to make sure that fish and other wildlife don't get sucked up though, as the pump will almost certainly terminate them!

[Bill Wright]

Use a timer relay that prevents switching more often than say, once an hour. Or use two float sensors at slightly different levels, the lower one for 'off' and the higher one for 'on'. Various relay configurations are possible if there are two switches.

Bill

[RobertL]

Since you are digging the pond, what is wrong with digging a pit under the pond and filling it with rubble (or one of those fancy plastic hollow boxes made for the purpose) and having the pond overflow into that?

Robert

[Rick Hughes]

have you seen such ? or ideas what they would look like ?

[Rick Hughes]

Is this what you mean ? ....

[Rick Hughes]

pond and filling it with rubble (or one of those fancy plastic hollow boxes made for the purpose) and having the pond overflow into that?

Won't cope with the water

The pond is not lined now ... and it fills & overflows regularly ... i.e ground does not allow it to soakaway ...

So digging a hole underneath even if it had a full land drainage crate would not work. Unless I put a hole in much bigger than the pond.

The ground here does not support soakaway construction ... it does not drain.

[robgraham]

the pond and filling it with rubble (or one of those fancy plastic hollow b oxes made for the purpose) and having the pond overflow into that?

This is clearly one of those evenings when everyone else seems a wally.

I have a bit bigger pond, and unless I live in an area of the country (Scotland!) which is seriously drier than yours, then a damp or bog bed is the solution. There are lots of plants that are well worth growing that love damp ground and all you need to do is to research how to make such a bed - I did so before the internet was the choice of information and I've had absolutely no problems whatsoever with maintaining the water flow through my pond system.

I know this may not seem to be in the ethos of "get-someone-else-to- tell-you-do-to-it", but I've given you the solution - now go and work out how to do it, as I had to.

Rob

[Rick Hughes]

But ... I don't want a damp or bog ? ......... I am building a pond. Nothing will grow in this ground it's an infill site, about 30' above natural ground level (they filled in a valley floor) mainly of waste from the steel works in the 40's & 50's

[gb]

Why do you think an overflow is needed?

If it is filled by rain water, then no more rain will fall into the pond than would have fallen on the area it occupied before the pond was dug. The rain must have run off somewhere so it will carry on doing the exactly that.

If the pond is stream or spring fed, a run off area must have existed before the pond. So again - no extra work is needed. Just dig the hole, stock it, and enjoy.

[Rick Hughes]

Because it fills with water, then overflows, any pond life would simply overflow out of pond.

Yes - agree, but it fills with rain water, rapidly ! As it's lowest point in garden any surface water on rest of garden is free to flow into pond ... so it's effective area is much larger than that of the hole.

I have in effect a 4' deep hole x 6' long ... it has no stream, fills up from rain.

For example I pumped out over 2' deep of it today, couple of hundred gallons. When it rains it fills up, then overflows, it's a simple fact that it does not drain away at all.

Hence I need to allow for a pumped overflow.

[Tim Lamb]

They are in the pond because they like it. Why leave? Floating stuff like Duckweed will gather at the run off spot and raise the level a bit.

You really don't want that. Surface water will carry minerals into the pond and stimulate growth from green algae (Blanket Weed etc.)

That isn't a pond. It's a sump. Where does it overflow to? Can you not provide a simple drain to some lower place?

I made the mistake of lining part of a *drain* on my land. Worked fine all Summer. When the water table rose in the winter, the liner *floated* and displaced the pond water. Bags of sand helped as did raising the sides by 6". 15 years on, it has settled down.

[Rick Hughes]

Well ... I have a hole in the ground, and when it rains it turns into a pond :-)

Measurement above missed a digit ... it's 4' deep by 16' long

It does not overflow to anywhere, just floods surrounding ground ... there is nowhere lower ... the ground is not permeable so does not support soakaways.

Hence this post ... I need to pump it away ... no other way to achieve this. I do have surface water drain a few metres away so have somewhere to pump it.

[Tim Lamb]

And the surface water drain pipe is higher than the pond level you wish to maintain?

I think we are all trying to head you away from an installed system requiring a safe power supply (buried SWA cable), ELCB, pump and piping plus a sump and float switch.

If gravity can't be used then bury a largish galvanised steel tank next to your pond and create a channel such that the overflow fills the tank. As others have said, float switches exist with a built in hysteresis so that your pump doesn't short cycle. You might get away with a cheap pond pump but if you are dealing with 0.75" of rain/hour worst case you can calculate the pump rating required. Submersible sump pumps start around

70ukp and you need to consider frost damage!

[Toby]

Yes.

Water in the pond will fill up to the point where the pipe is horizontal, and if the water arriving into the pond is slow, will just trickle over, however, if you get a deluge of water, it should start a syphon, which will actively suck the water out, the longer the pipe that goes down into the pump side, the stronger this suction will be (unless it it too close to the bottom, then that will restrict the flow).

I am guessing that 32mm waste pipe would do the job here.

You will need to protect the pond end of the pipe, to stop stuff getting sucked out, maybe two of these attached to each other at the open end with cable ties, then a hole cut for the pipe.

Toby...

[Rick Hughes]

So ... (lining up thoughts here) if I arrange horizontal sect of pipe to be just above normal water level, and have a 2 vertical section in the pond, and then have a 300mm vertical section in 'sump'

How do the float switch work on Hippo pumps .. the catalogue pic looks like a rectangular box attached to a cable/pipe.

Understand it could switch on when water reaches it, but how does it get any hysteresis .. if you make it longer or shorter (not disputing just curious) Not even sure what it physically is.

[Rick Hughes]

Drain is higher than water level of pond ... so can't use gravity feed.

Was thinking of using a plastic cold water tank, in a brick lined hole. N shaped drain pipe to obtain siphon that Toby explained ... and a HIPPO submersible pump ... They can be had for £54 (or less ... have to calculate aprox flow reqd)

Or the alternative a 12V bilge pump, these are expected to short cycle as the float bounces around all the time on a boat.

12V would avoid any issues around power supply.

[Toby]

There is a weight in the rectangular box, and I think, a magnet, so it will hold off at the far end of the box until it is tilted towards the cable quite a lot, then the weight falls towards the cable end and activates the pump.

The cable can be clipped to the pump to adjust the length, so the pump comes on later or earlier, as a shorter cable will mean the angle is greater for a set depth of water.

[Tim Lamb]

Sounds fine. Maybe size it so a standard paving slab can act as a cover.

Consider pump head when doing the sums. Pumping uphill dramatically degrades the output performance of centrifugal pumps.

The siphon may not actually siphon but it is certainly better to take the overflow from below any floating crap.

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