cacluating pump for pond plus stream

[garyoddou]

I am trying to figure out how to calculate the pump I should buy based on the following:

1. small pond (500 gallons)
2. a stream after the pond of around 20 feet (6 inches deep and 36 inches wide),
3. waterfall at the head of the pond of 3 feet
4. a distance of about 20 feet or less from the end of the stream to the waterfall.

I've looked at some pond sites and they ask about the # of fittings and the number of 90 degree angles to help calculate the head size. What are they calling "fittings" (like a backwash valve would require 2 fittings??). How are "fittings" calculated? If I used a flexible hose to from the end of the stream back to the waterfall, how many 90 angle fittings would I have to use?

Here are some additional questions I have if you could help me:

1. I see pumps that have very different horsepower sizes but similar gph output. What are the other variables that determine the strength of flow for a pump if the horsepower can be so different (1/15 to 1/4 I've seen for a similar gph output).

2. I have read that mag drive are the best. Most of the pumps don't say what kind of drive they have. How do you know?

3. I have a pre-formed pond. To go from it to a stream, would I need to cut out the part of the pre-form wherever I want the stream to start?

4. Seems like there are a zillion manufacturers of pumps, from Japanese types to American and others. Are there certain brands that are considered the best quality?

As you can see, I'm a newbie. Thanks for any help you can give me.

 

[sissy]

mag drives get clogged easly .look for one that uses less energy but has a high head for the length of hose and size of hose you are using .Remember a smaller hose will only pump so much water .I used a sump pump hose for 10 dollars to get the amount of flow I wanted at a cheap price and been using it for over 4 years now .I would just lay the stream liner over the preformed you don't want the water to run under it and threw the cut part .Your stream is on a slope you will get better waterflow .It would depend on your budget for a pump .

 

[sissy]

The mag drive pump thing is only from my own experience with them some work some don't .Just like submersible verses external

 

[Waterbug]

I've looked at some pond sites and they ask about the # of fittings and the number of 90 degree angles to help calculate the head size. What are they calling "fittings" (like a backwash valve would require 2 fittings??). How are "fittings" calculated? If I used a flexible hose to from the end of the stream back to the waterfall, how many 90 angle fittings would I have to use?

This deals with friction loss. Water has a harder time flowing thru a 90 degree bend because energy is needed to change direction. Newton's first law.

Friction loss do to fittings should not normally be a high concern. Diameter of the pipe should be. Increasing from 3/4" to 1" for example can make friction loss go from a lot to almost nothing. The fittings then kind of follow that. So if you just compute the right pipe diameter you're 99% there.

How could anyone say how many 90's you'd need? Answer is somewhere between 0 and infinity. Kind of up to you.

Here are some additional questions I have if you could help me:

1. I see pumps that have very different horsepower sizes but similar gph output. What are the other variables that determine the strength of flow for a pump if the horsepower can be so different (1/15 to 1/4 I've seen for a similar gph output).

Pump and propeller design. A pump can be designed to move more water to a lower head or designed to move less water to a higher head. Some pump designs just circulate water, zero head, and have a unique design for that purpose. So generally you'll see something like "max head". One might be 25' while another is 10'. In generally the 10' max pump will move more water at say 3' of actual head than the pump designed to have 25' max head. However, if the head you actually need is say 15' it doesn't do you any good to buy the 10' max pump because you get 0 flow.

Good pump manufacturers publish flow amounts and power used at different heads. But that's way more info than most consumers want. A consumer's job is to consume, not study.

2. I have read that mag drive are the best. Most of the pumps don't say what kind of drive they have. How do you know?

You know when a seller doesn't give you information that they're targeting a certain type of consumer. Someone who's job it is to buy stuff, any stuff, lots of stuff. It's a huge market.

Many pumps have the same guts. "Manufacturers" just make the plastic case and propeller, the propeller design is important however, but not hard. Propeller design has a long history and well understood. So some sellers package basically the same pump several ways. One with no info except something like "works great" for the consumers. Another way with something like "for 500 gal ponds" for people that care a little. And another with the complete chart for different heads for people who care. Each level is a smaller and smaller market, and that seems to be getting worst and worst.

Here's a good explanation of mag vs direct drive pumps. Google is your friend.

3. I have a pre-formed pond. To go from it to a stream, would I need to cut out the part of the pre-form wherever I want the stream to start?

Absolutely not. Never a good idea to cut a preform. The plastic use has a grain. Cutting it even a little can cause splits.

Just lay the liner over the pond edge and into the pond. Make sure there is some gap between the top of the pond and liner. A few stones is fine. This is just to stop the chance of wicking water.

Trying to seal the liner to the pond is not needed and can cause wicking problems.

4. Seems like there are a zillion manufacturers of pumps, from Japanese types to American and others. Are there certain brands that are considered the best quality?

A zillion manufacturers...but zillion squared opinions. So absolutely there certain brands that are considered the best quality, but that changes from person to person. What's that worth?

The reason there are so many has more to do with marketing. If you sell the same basic pump in 100 different cases you have the chance to tailor packaging to different types of consumers.

Also you get more eyeballs. Say a store carries 500 "different pumps and 100 of those are mine. I have a pretty good chance of a consumer buying one of mine. And I've tailored my packaging 100 different ways to answer that one question a consumer might have. "I have a green pond so I'll buy the pump that says 'clear water'." Or "I'm concerned about electric cost so I'll buy the one that says 'uses less electric'." All the same pump and none of the claims just true enough to not be sued.

I am trying to figure out how to calculate the pump I should buy based on the following:

1. small pond (500 gallons)
2. a stream after the pond of around 20 feet (6 inches deep and 36 inches wide),
3. waterfall at the head of the pond of 3 feet
4. a distance of about 20 feet or less from the end of the stream to the waterfall.

The most serious issue you have to design to is the pond size vs stream size.

When you first turn on your pump there is a delay until you see water falling back into the pond. First the pipe going to the top of the stream must be filled, then water collects in the millions of little voids or pools in the stream until each is full and overflows. Then just the distance that must be traveled.

If say your stream size needed to completely fill with water before it could overflow back into the pond it would take 225 gals. Your pond would be 1/2 empty. You can design for this by adding an auto fill for power outages. You can pre-fill the stream, add water to the pond. When the pump is turned off the pond will probably overflow (depends on design).

But there is another factor. If you add a 10,000 GPH pump, water can only move so fast, you could completely drain the pond before water can get back to the pond. It's really tricky to design and I think experience is the only method. Do what you can to minimize the risk and be prepared to adjust later.

 

[garyoddou]

Thanks, Sissy and Waterbug for taking the time to reply. Waterbug, I have a couple of questions based on your info.

Fittings and hose size
Okay, so you're saying if I have a 1.5 inch hose all the way around and only 3-4 fittings (like a check valve and ), then the fittings issue is not much of an issue in considering the pump gph requirement. Is that right?

Mag vs. Direct
I read the article. thanks. Sounds like for my need (relatively small operation), a mag drive or a hybrid should work well.

Transition from pond to stream
What is not clear to me is how the water overflows from the pond's preformed shape to the stream without the pond overflowing everywhere (on all sides). Doesn't the start of the stream have to be lower than the water in the pond? You mention about the pump at the end of the stream returning to the beginning of the stream (unless I misunderstood), which makes me think that I might have given the impression these are two physically separate water flows (one to the pond and at a different place in the yard, one to the stream). So I'm confused. Can't one pump, at the end of the stream be used to pump the water from the stream back up to the waterfall to recirculate the water to flow into the pond and then to the stream?

I can't find any place that talks about this configuration (waterfall, pond and stream) and how the stream affects pump needs. I should probably just pay a professional to calculate what I need and I do the labor to install everything.

Thanks again!

 

[dieselplower]

Wow I hope I misunderstood that last post. In a pond with a stream and a waterfall, the pump goes in the pond, which I assume is the lowest point of the water feature. It pumps the water out of the pond, up the hill to the top of the stream, where it flows back down into the pond. OK I see in the OP it says the stream is after the pond. So the stream is lower than the pond? Where does the stream end? What keeps water from flowing out of the stream? I guess in this crazy setup you would put the pump at the end of the stream and pump the water back to the pond. That's just crazy. Good luck!

By the way, no offense. I probably dont even understand what you are saying correctly. Is there a picture of this? Is it built yet?

 

[HARO]

Your question is a bit confusing. Do you realize that the pump has to sit in the pond, from which it pushes water to the end of the stream or waterfall, to flow back into your pond? It sounds like you want the pond to overflow into the stream.
John

 

[garyoddou]

Diesel Power and Haro,
Yes, I wanted the waterfall to flow into the pond and then there be overflow from the pond to the stream and the stream would end in a "box" covered by rocks for appearance sake and be pumped back to the waterfall. Not sure why that's so crazy other than it differs from what most people do. However, since it does create the problem of how to get it from the pond preformed mold to the stream, I could easily go from the waterfall and stream to the pond. I guess that would make things easier and I wouldn't have to worry about whether the stream after the pond would affect the pump characteristics.
I am still not clear on the head part. It seems like the word is used for different things in what I've read (dynamic head, total head, vertical distance from the top of the waterfall to the pond surface being a type of head, etc.). Obviously, someone who is familiar with ponds wouldn't be confused.
thanks for the helpful discussion.
Gary

 

[sissy]

the stream should be part of the waterfall .A pond that is solid cannot overflow to a stream .

 

[garyoddou]

Okay, I'll go from waterfall to stream to pond; sounds easier all the way around. Currently, the preformed mold is set up (it's a used one that I got off someone) for a 3/4 inch flexible hose so was not intended to have a waterfall, I guess. If I add the waterfall, I'll have to use a more powerful pump and it seems like 1.5 inch is a common inlet and outlet size. I assume I should not go from 1.5 inch inlets and outlets to a 3/4 inch tubing for the supply and return. Right now, the mold has both the supply coming in and the return and they're both for a 3/4 tube. If i should not go from 1 inch or 1.5 inch to fit the more powerful pump to the 3/4, is it kosher to cut a larger hole in the prefab mold and I assume there are the appropriate fittings to make a water tight seal again. Thank you all again for your guidance.
Gary

 

[Waterbug]

Fittings and hose size
Okay, so you're saying if I have a 1.5 inch hose all the way around and only 3-4 fittings (like a check valve and ), then the fittings issue is not much of an issue in considering the pump gph requirement. Is that right?

Yes, that's right...if 1.5" hose is big enough to drop friction loss to almost zero. Depends on the GPH. If the pipe diameter is good a few 90s is going to mean a little bit of loss. You can see the difference for by doing the calculation just for straight pipe, then add a single 90. The difference in loss is the cost of a 90. When you're actually installing you can kind of do the calculation in your head and maybe think of another layout that would work with fewer 90's. Certainly possible to plumb a stream with no 90s.

Transition from pond to stream
What is not clear to me is how the water overflows from the pond's preformed shape to the stream without the pond overflowing everywhere (on all sides). Doesn't the start of the stream have to be lower than the water in the pond? You mention about the pump at the end of the stream returning to the beginning of the stream (unless I misunderstood), which makes me think that I might have given the impression these are two physically separate water flows (one to the pond and at a different place in the yard, one to the stream). So I'm confused. Can't one pump, at the end of the stream be used to pump the water from the stream back up to the waterfall to recirculate the water to flow into the pond and then to the stream?

Yes, confusion on both our parts...why drawings are so much better than text. I assumed the 500 gal pond was at the bottom.

The thing at the bottom of the stream, whatever you call it, pond, reservoir, basin, has to hold enough water to not run dry in the time it takes the pumped water to make its way thru the falls, stream, whatever.

A perform can be made to overflow in to stream but it's very hard, very risky and more than buying a PVC liner which is comparable in strength imo. Perform only seem easy...they're harder in every way. If you really want to a heat gun can be used to soften the plastic and bend it over and down to form a lip and lower point. You have to be really careful on the install to get the pond pitched a little toward the lip. It will work if level, or even pitched the wrong way, but any settling is probably going to mess you up. So pitched forward give you a little grace.

I can't find any place that talks about this configuration (waterfall, pond and stream) and how the stream affects pump needs. I should probably just pay a professional to calculate what I need and I do the labor to install everything.

I haven't seen any either. Most people just wing it I think and take and fix the problems later.

 

[Waterbug]

Okay, I'll go from waterfall to stream to pond; sounds easier all the way around. Currently, the preformed mold is set up (it's a used one that I got off someone) for a 3/4 inch flexible hose so was not intended to have a waterfall, I guess. If I add the waterfall, I'll have to use a more powerful pump and it seems like 1.5 inch is a common inlet and outlet size. I assume I should not go from 1.5 inch inlets and outlets to a 3/4 inch tubing for the supply and return. Right now, the mold has both the supply coming in and the return and they're both for a 3/4 tube. If i should not go from 1 inch or 1.5 inch to fit the more powerful pump to the 3/4, is it kosher to cut a larger hole in the prefab mold and I assume there are the appropriate fittings to make a water tight seal again. Thank you all again for your guidance.
Gary

We might have some more confusion on what this prefab is. You should post some pictures and close ups of the edge, thickness of the plastic. The most common prefab we call a preform. It's normally a vacuum formed plastic and it has certain properties like you shouldn't ever cut it because of grain type issues. Melting and reforming is possible but very risky because the plastic is so thin.

Could be you have an injection molded pond, or even fiberglass. Don't know. Those can be drilled and new fitting added.

But just because you have those fitting you don't have to use them. Cap them off. Run the pump hose up the side of the pond, under the stream liner and in the stream bed (before you lay the stream liner) all the way to the top. Saves a lot of digging.

 

[garyoddou]

Waterbug, okay, I'll definitely plan to have the stream flow into the pond. It's dark now so can't take a good picture of the preform, but it's a black, hard, probably 1/8 inch plastic/vinyl. Definitely not fiberglass. It's semi-rigid (more rigid than flexible) and seems pretty tough. So if I capped the supply opening into the preform and had then ran the 3/4 inch flexible tubing to the waterfall under the stream liner, the tubing would just run along the bottom of the preform, then on top of the lip where the stream flows into the pond (but hidden under the lip of the run-off from the stream and then similarly, hidden at the top of the stream and up the waterfall? Seems like a good idea and simpler than digging another trench alongside the stream from the pond.

I am looking at a Pondmaster submersible with an 18 foot cord, so the same thing kind of applies. The cord comes out of the preform, over the lip, hidden by rocks and other stuff surrounding the pond and do most people run the cord inside pvc piping underground to the outlet? Any code issues I should be aware of (well, I'm in California, the most regulated state in the US, probably, so there's surely some code, whether it makes sense or not.

Thank you for your help and questions. It is definitely moving things along.

 

[Waterbug]

I don't think there is any code for the cord...which is a little strange. My thinking is it is a consumer device. Just like you can run an extension cord across the lawn to plug in something. Lots of problems with it, but building codes stop at construction. From there people can live as dangerously as they like.

I do put the cord thru PVC conduit, or PVC, or ABS, whatever I have. It does take a pretty large diameter, like 1.5" min I think. The cord laying on the ground looks ugly imo and is a tripping hazard. So I like it buried. Which means the next day I'm going to dig a hole for a plant and cut the cord..every time. So conduit is my friend.

 

[garyoddou]

Alright. I'll put it in PVC. If you don't mind another question, here goes. I am trying to figure out how to go from the pump to the waterfall weir and where filters go in and the size of tubing. It sounds like there is supposed to be a filter in the water weir as well as one before the pump. Is that true? And if I get a pump (Pondmaster, for example), the inlet and outlet sizes it says are 3/4 inch but most of the water weir inlets for 14 inches or bigger are 1.5 or even 2 inches. Do you just buy adapters to go from a 3/4 inch size to 1.5 inch, and even if you can, is that advisable for the water flow?