Ponds Waterfalls, Longer Streams and Pumping Power
Hi Peter, Well I visited a pond supplier over the weekend who also builds ponds and waterfalls. There were a couple of water features on display, one in which I'm thinking on building. It starts with a waterfall and disappears into the ground once it reaches the bottom of the falls. He said he's got a flexible liner filled with 1/2 " washed gravel, which acts as a reservoir and also as a filter. Inside of the gravel he basically has a bucket with a pump inside with another bucket turned upside down fastened to the bucket on the bottom. This casing, which holds the pump, is then drilled with 1/4" holes to allow water in to run the pump. There is a hole out the side for the flexible water line and power. Have you heard of this and if so how does it work?
Here is where I'm at. I want to build a small waterfall, approx 2-3 feet high, that flows into a creek that is 18-20 " wide and 2-4" deep. The length of the stream from the falls to the reservoir is 50' (that is in a straight line.) My stream would have 2 slight bends in it, which will make it's actual length longer. The problem I am having is how big do I need to make my reservoir? I understand that when the pump is shut off it (reservoir) needs to hold all the water in the stream.
I have also seen where instead of doing as described above they use a wire mesh over the top of the reservoir and cover it with smaller rock. How does that work? The water feature above has a submersible pump that pumps 4000 gph,with 2 inch flex.It has quite a bit of water. If you could, could you tell me what size of pump I would need? Thank you for your time and effort.
Shawn.
The method of filtration you mention at the beginning was a popular method of filtration some years ago and evolved into what is commonly called 'the spider filtration system'. It works in the same way as a biological filter in that a colony of oxygen dependent bacteria build up in the gravel over a period of weeks that digest any detritus or organic matter in the water as it gets trapped trying to pass through to the pump. It works brilliantly if it runs 27/7, but if you turn it off for more 2 hours the bacteria begin to die and the process of building up the bacteria has to start again. This then means that the filter system clogs up with too much crap and you are forever cleaning it out. It should only need rinsing through with rainwater or pond water once every six months at the most.
However your proposed creek could be an algae factory, depending on how hot it gets round your way and or how much sun it gets and also how much detritus will fall into it. My guess is that you will need as much filtration as you can get.
You don't tell how much of a drop the creek has from one end to the other. Lets guess that it is about 1 foot, in which case you will need a pump capable of delivering 2000 gallons per hour to that height to get a nice even flow over the water falls and down the stream. ( You are dead right - the stream and the header pool in the water falls should hold water when the thing is turned of. Effectively the stream is a one long, or a series of, long header pools. Its all in the 'Perfect Pond recipe Book').
To get the water delivered to over 50 feet away you will lose approximately 1000 gallons per hour worth of power (that is delivery from the pump) and then give or take the head at 4 ft the 4000 gallon per hour pump mentioned below would do nicely.(The 2ins hose is good too - keep the hose the largest the pump can take and keep fittings to a minimum unless you want to throttle back the pump.) The minimum size of pump required would be 3500 gallons per hour.
When you turn this thing on over 100 gallons (104) is going to disappear before you see any water coming back down the stream. When it is in full flood, you may find 200 gallons are required to just cover the pump or the filter bed. I'd be inclined to double that to be on the safe side and double that. It would take care of evapouration and some of the imponderables that haven't occurred to me. So if you had a reservoir 5ft x 6ft x 2.5ft that would give you a gallonage of 468galls - as an example.
The pool above is just about small enough take a grid of metal or weld mesh. It can be cut to fit and can be held in pace with edging rocks or hooks or brackets embedded in the structure of the pool skeleton (which can be blockwork or timber).You can cover this with rocks pebbles and gravel . If the gravel is fine, a fine net mesh can be put over the metal grill. Cut a way a fairly large square in the grill to gain access to the pump quickly and efficiently. Use and offcut larger than the square to make a trap door over the hole, hinged in place with wire loops or cable ties.