Some pump and filter questions...

[Shelly]

Greetings Everyone. Thanks for allowing me to join this forum and seek advice. I'm planning a backyard waterfall and stream, and small pond. This will be my first.

Some info about my project:

Pond

> Roughly semicircular in shape. About 55 square feet of surface area. Two feet deep. On-line calculators suggest about 750 gallons.

> No fish, but some plants (lilies?).

Stream

> The stream will be built on a raised curved sandy berm about 15 feet long. The berm width varies from 3 to 4 feet, which provides some space to play with the direction and flow of the stream.

> The stream has an upper waterfall (a 22 inch weir plastic spillway with 2 inch hose fitting and max capacity of 7500 gal/hr), and a middle fall with 20 inch weir, and a lower fall with 48 inch weir. The lower fall is actually two separate falls which empty into the pond at two different locations. One of the lower falls has an 18 inch weir and the other has a 30 inch weir.

> The upper spillway is about 4 to 4.5 feet above the pond surface (water level).

> The length of the run from the optimal location for a pond skimmer to the vicinity of the upper spillway is about 17 feet.

> The stream and pond are in full sun. This Fall, trees will be planted. But, they won't provide significant shade for at least a few years.

> With no fish, I assume the water does not have to circulate 24 hr/day, so the pump would run off a timer. When the pump is off, water from the stream drains into the pond; there is no reserve tank.

> I'd prefer a high efficiency, durable external pump, but it would have to be located behind the spillway to keep it out of sight and to keep the noise to aminimum. It would be nice to have a variable speed (flow) pump, such that the pump output (flow) could be reduced or increased with a corresponding change in electricity usage. Variable output flow would help with "tuning" visual/audio experience. A submerged pump would be acceptable, but less desirable, because the pump and the hose might be visible and would require occasional retrieval from the pond to clean.

On to my questions:

> Using the 150 - 200 gal/inch of weir guideline found in various posts and articles, the required pump capacity calculates to 7200 - 9600 gal/hr for a 48 inch weir. Is this correct? Seems like a lot more than most builds I read about.

> Is this pond big enough to continuously supply the stream/falls at that rate of flow? Will the water level in the pond drop drastically when the pump is running?

> Any suggestions for pump brand and model? On paper, the Aquascape AquaForce Pro 4000-8000 has some nice features, even if it is a submersible type.

> I read that pumps push but don't suck water. If an external pump is used, with a swing check valve and priming pot, could such a pump be placed at an elevation above the pond surface water level (say two feet) or is elevating the external pump a bad idea?

> I'm doing a lot of reading about filtration too, but am totally confused about what's needed to filter a no-fish pond. Do I need a bottom drain? A skimmer? I'm familiar with sand and gravel filters used in swimming pools, would having only a pump leaf pot and SG filter work OK?

Anyway, thanks for taking the time to read my post. Any and all advice,
suggestions, cautions are appreciated.

Regards,
Shelly

 

[HTH]

The skimmer is mostly for stuff that falls into the pond so yes on that.

Bottom drain makes the pond easier to clean. Dead leaves etc all do down. I think you can do without.

Too much pump I think. The pond will be like a pot boiling then a peaceful water garden. OK but forget about lilies and any plant that floats on the surface.

 

[addy1]

If you have a check valve on the line going into your pump, you could have the pump higher than the water by 2 feet.

 

[HARO]

One question, if I may; does ALL the water go over the first two weirs before it hits the 48" combination? If so, you will have a veritable Niagara going over those two falls! In my experience, 100 gallons per hour per inch of weir width will give you a 1/4" sheet of water, which is a nice flow for most applications. So 4,800 gph would be appropriate for the lower falls. However, this would mean a sheet of water at least 1/2" thick over the two upper falls, which may be a bit much. And 9,600 gph over a 22" falls would be water an inch deep! It may be more than you need.
John

 

[Shelly]

Thanks HTH, addy1, and HARO for the advice.

It's good to know that if needed, the elevation of the external pump can be a few feet above the intake in the pond.

Yes, in theory all the water would go over the 22 inch spillway and then the middle (20 inch) fall and then flows over the 48 inch spilt lower falls.

However, the valuable feedback you guys are giving me is 7200-9600 gal/hr is too much water flow. Maybe it would be better to target 100 gal/hr and reduce the size of the weir of the split lower falls maybe (40 inches?). That would call for a 4000 gal/hr pump?

Thank you.

 

[HARO]

I think that's what I would go with, and possibly even split the flow, with half going to the upper falls and the rest coming in at the lower level. That would give you a fairly even flow throughout. But it's YOUR pond, and everyone has their own preferences. Just throwing it in for your consideration.
John

 

[sissy]

Get ball valves to adjust the flow also .They help a lot

 

[bbently]

Thanks to all of the posts about possibly too much flow. Thought I missed something myself, but kept going back over this. We all have our theories and reasons, but my gut tells me that less than half of the 7200 to 9600 gph rate should be fine for the quantity of water in this system.
Stepping out of the box for now, next batter please.