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Rehabbing a pond -- what next?!?!

Posted by gpf11 none (My Page) on
Sun, Jun 1, 14 at 15:03

Hi! Longtime lurker, first time poster.

Moved into a house with a beautiful pond last summer. Now -- not as beautiful. A heron and racoon ate up the goldfish. Leaves and a history of way too many fish (I think) made the water gross. And - to top it off - the waterfall pump stopped working. I just drained it and am looking for advice about the next step.

The big pond (pics below) has pebbles and rocks on the bottom. Before I muscle all of them out and figure out where to put them, I wonder if there's another way to get it clean.

Too, I imagine the pebble stream is a main part of the filtration. The water is certainly dirtier since the waterfall stopped working. Since the pump is wired to a switch and uses underground plumbing, I think replacing it on my own might be daunting. The pond guys I've talked to say they'd recommend pulling it out and using a submersible, but the elevation change seems significant. Any advice y'all could provide there would be helpful.

Too, this concrete pond is probably at least 40 years old. It has several cracks that have been repaired several times. It looks like the downhill side of the pond has sunk, as the waterline ought to be much higher on the uphill side. My thought was to find a way to build up the sunken side, create a higher rock wall, and put in a liner to restore the water level to the uphill side. I imagine using a liner would present a risk of puncture and leakage with rocks and concrete under it.

Thanks for any advice!

---gpf11

The pond system is in a sloping yard. At the top is a waterfall into a small pool. Here's a view from the top:
Pond Pic System Wide

The pool drains into a pebble filled stream and works its way down to a larger pond. Here's a shot of the stream and some intermediate falls (there are 7 total):
Pond Pic Bic mini fall

The stream falls into a large pond at the bottom.
Pond Pic Bic final fall

Pond Pic Big Full

Here's the big pond drained:
Pond Pic Bic big empty

The pond is fed by a pump housed outside the large pond through underground plumbing. It runs through a switch in the house. Here's a wide shot of the pump housing:
Pond Pic Pump Wide

Here's a closeup (which also shows a crack in the concrete that appears to have been repaired several times):
Pond Pic Pump Close

Here's the pump works on the inside of the pond in a fish cave:
Pond Pic Bic pump inside


Follow-Up Postings:

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RE: Rehabbing a pond -- what next?!?!

I don't understand out of pond pump systems and priming and freezing etc. and will let others handle that part of the problem. However, I do wonder if your pump is actually broken or beyond repair. Have you checked the circuit breaker? Does it have a ground fault circuit interrupter? It probably should, and dampness and other minor wiring issues could be continually tripping it. That shouldn't be that hard to check. Can you tell that there is indeed power at the pump?

That appears to be a beautiful pond and it doesn't really seem to be all that dirty. I think if it were me, I would just go after it with my power washer and bale the crud out and not worry about the rest. Water and plants can hide a lot of stuff. Your yard doesn't appear to be all that steep. Perhaps it just doesn't show up. I would guess that you could use a submersable pump. Again, you should first determine if the other pump is bad.

If you have read my posts, you know that I agree that a stream can do a great job of filtering. I mention it because unless you have done a stunning job of stream cleaning after the pump failure, it doesn't appear that the stream had many or any plants in it. I suppose the gravel does something, but the plant roots are invaluable; you should get some.

So sorry about the varments. Fortunately, I have only had minor problems and have little personal experience. I have an electric fence for my garden and it generally does the trick. I would think that it might work for you although it certainly wouldn't help with beautification.

If you really want to raise the level and use a liner, I just want to point out that the liner is very tough and I doubt that most rocks, if not removed, would be able to poke through unless you went jumping around in the pond with heavy boots. It might be hard to hide the liner unless those top flag stones are loose or could be popped off. Perhaps waterbuguy knows something about that?


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RE: Rehabbing a pond -- what next?!?!

Thanks for posting pictures. Makes this soooo much easier.

I can only add to chas045's excellent post.

Streams are great filters for Water Gardens. But there can be confusion over the terms "filter" and "clean". Many people new to ponds think "filter" means "clean" and that's not the case. A stream is great for removing ammonia which is great. A stream will also grow macro algae (string algae, etc.) which will stop a pond from turning green. I call that a filter, other people call it dirty.

What a stream doesn't do is remove dead stuff that decompose and sometimes cloud the water. The stuff you're now shoveling out. There are things in bottles that say they will magically make that stuff disappear but the only thing they make disappear is your money. To me the best solution for this type of pond is a vacuum(s).

One issue is people new to ponds often use terms like "dirty" which can mean many things. That can lead to many solutions that don't work for the kind of dirty you have. So it takes a bit to narrow that down.

Pond guys recommend things they understand. Maybe they only work with submersibles. I like submersibles, but you already have an external. Using a submersible is going to be a lot of work imo. Maybe that's what the pond guys were thinking...$$$.

Disclaimer: To me pond guys are below used car sales people in my book. There are probably some good ones out there, but I've never seen one. You are way better off with no experience than doing what these dudes do.

The reason I say the submersible is more work...Where's the electric cord and pipe/hose go? Up over the side of the pond I assume. For liner type ponds that's not too hard to hide. For a concrete pond it's a problem. More mortar and rock to hide that, not easy to do well. The hose/pipe has to be connected to the pipe by the external. The power cord plugs into what? A new outlet. That sounds like more work to me than a new external. Not the end of the world, but has to be done.

You should measure the elevation change, what pump people call "head". You measure from the water level in the bottom pond (not the pump) to the outlet pipe at the top. Easiest way is a water level. Lots of Youtube videos on how to make one. Pretty darn easy and cheap to make, or buy one that screws onto your garden hose. They're more accurate than a laser level too.

The reason you want to know the head is because that will help you pick the right pump. Pumps are designed differently to handle different heads. If you see a pump that has a max head of 30,40,50' you know it's designed differently than a 10,20' max head pump. Most people say higher header = better pump, why not get that even if only 5-10' of head is needed? The deal is the higher max head pump will use more electric for the same amount of water movement. That costs you $$$.

Normally when we're talking about this type of DIY concrete pond we're talking about leaks. Apparently this pond isn't leaking too much, which is all kinds of unbelievable. I see they have a toilet auto filler installed...auto fills are a great idea (not toilet types but in general)...but in this case I kind of wonder if the auto fill is there to make up for leaks.

An EPDM liner could be set over the concrete rocks. I'd move lose rocks out. I would use an underlayment, carpet, carpet padding. EPDM is very tough.

Adding a liner would make switching to a submersible easier.

If it was my pond or was asked to fix it I would remove the entire thing, lay a liner and mortar rock over the liner. But that's just me. It is a lot of work, but I think less than most people think. Concrete scares people. It actually breaks up pretty easy. I can normally find a place in the landscape to use the broke pieces, like to build hills.

It really depends on the owner's desires and budget (both labor and $$$).


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RE: Rehabbing a pond -- what next?!?!

I just want to comment on the first point on wbg's post regarding 'filtering' from a stream and his contention that visible crud isn't being removed. wbg has done far more experimentation than anyone could expect on a general garden site and I believe his comments should carry more weight than most. None the less, I question the above. I do get lots of string algae in my stream. It is also filled with lots of other plants including sweet flag that anchors itself very well with huge root systems and water cress that also creates far less anchored but still large fine roots.

Several years ago I posted about the benefits of my stream. Here is a modified portion:

I found that water cress (and other plant) roots would trap the fine crud circulating from pond and stream. On occasion I would yank out excess growth and gobs of crud would be removed with it. Admittedly this also stirred up more crud but it was almost immediately removed by other roots and perhaps the filter. The actual cress and fallen leaves etc. would catch the algae that I would grab out with my hands. I recently had the sense to use a toilet brush.

When I said 'gobs of crud', I meant a massive, muddy, and slimy (from string algae) mass of dirt that was removed. If I only removed a couple of water cress/algae clumps, I would just stir up a small area of stream that would immediately turn into a turbid brown collection of visible fine particles and brown milk. This would clear from the stream in a few minutes and from the pond in a few hours. If I was more aggressive and removed most algae and perhaps some of my more tenacious plants, the stream and pond would turn into the Yellow River in China, but still within a day everything would be clear again.
I believe the fact that I can actually see the dirt removed, and see the dirt that escapes from the roots that then looks like the turbid mess that no one wants, that then again disappears and reappears on roots a week later, clearly indicates that plants can filter crud from a pond.

I actually like the look of string algae on the rocks, and I don't really mind some of the masses of it in the stream, but I am happy to have less of it too. For one thing, my stream becomes naturalized and it is often hidden among the plants. I have linked my original stream post below.

Here is a link that might be useful: stream post


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RE: Rehabbing a pond -- what next?!?!

I think we're talking about different things. Yes, plants could trap clumps of dead string algae, and the plants could be pulled out to remove the trapped clumps. So in that sense they are good filters. But to me there are easier ways to remove clumps of dead string algae, so I personally wouldn't consider the plants a filter. Or maybe a very good filter would be a better term. But each pond owner has to decide that for themselves.

And yes, pulling out plants does stir up a lot of stuff. But was that stuff removed from the water or was that created by the plant? I don't really know. Probably a little of both. What I do know is plants grow roots and some die. I do know bacteria will grow in gravel and die. Such is life. I've grown plants in fairly clean wet gravel in a pot outside of the pond, for starting new plants. And I only add clean water. After a few months when it's time to repot the gravel is very dirty and stinky. I think that dirt was created in the pot by bacteria and the plant.

But if we do say the plants are trapping dirt we have to ask 2 questions to consider it to be a filter (whatever our own personal definition of a filter happens to be). How much and how do we get the trapped dirt out.

The amount of crud suspended in even a clear water pond is shocking. If a pond had a huge plant area, maybe 2 or 3 times the size of the pond, like is used in some waste treatment plants, then sure, great filter. But for most backyard ponds I don't personally think a small area really makes much difference. And I think the net result is more waste from dead leaves and roots. I do like plants as part of a pond for looks, But if we're only looking at waste I'd say plants add more waste than they remove by a wide margin. Sorry.

Removing the trapped waste by pulling out the plants would certainly remove some waste (created by the plant or trapped), but I think a lot ends up in the water. Maybe if the plant area could be isolated and the dirty water removed more would be removed.

I really, really wish plants did nothing but great things in a pond. I love Water Gardens, lots of plants. I'm not a big fan of sterile Koi Ponds. But I think being realistic makes things easier. I've moved from having plants directly in the pond to isolating them into their own beds in and around the pond. It just makes life easier.


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RE: Rehabbing a pond -- what next?!?!

Wow, thanks for the detailed and helpful discussion.

I think I've cooled on the idea of bringing in a "pond guy" before I really clean it out. Looking back at the pictures, they sure don't do justice to the amount of muck that was at the bottom.

This afternoon, I dismantled the fish cave where the pump intake is located. I hadn't ever realized just how deep the deepest point was. There was at least 18" of small pebbles and muck at the bottom, making the deepest spot about 4 feet. Got a fair amount out -- but looks like I've got my work cut out for me over the next few evenings.

Re: pump

Now that I've got it cleared out a bit, I'm going to try to fire it up again before making the call to dismantle it. It may have just been clogged. It definitely is still getting electricity, so I'm going to hold out hope for a bit longer.

Re: Concrete work

There are some pretty serious cracks. I think I'll have to do *something* after I clean it out, because I'm pretty sure the muck was plugging some leaks. There's a patchwork of repairs that's calling for a more comprehensive solution. I hadn't thought of knocking it out and starting from scratch and can see the allure. Any repair is going to be work -- so why not put in a little more effort and get it right? I'm going to keep plugging away at cleaning it out and see if I'm moved to break out a chisel.

Re: Stream plants

Over the last year, I definitely spent time pulling weeds out of the stream, stirring up the dirt, and clearing out the gravel. I have no other filter. With lots of trees, lots of fish, and an inattentive owner (!) there has steadily been an increase in dirtiness. Once I get it up and running, I'll probably keep the plant out at first and try a controlled introduction.

So, plan for now: plug away at getting everything cleaned out, test the pump again, and look forward to playing with some mortar and concrete.

Thanks guys!


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RE: Rehabbing a pond -- what next?!?!

If it is too much to do this year you might can do it in stages. Fix the lower big pond and a few of the waterfalls for this summer and work on the rest over time. A 'dry' stream bed would look good with the pond and you could divert any water from the top portion of the stream until you are ready to have the whole thing working together. A few feeder goldfish with an inexpensive plant (any type of mint) sitting submerged in the cleaned out smaller ponds will keep the mosquitoes at bay.

Look for a submersible pump on Craig's list to use in the lower pond. I have gotten some great deals on Craig's list for pond equipment. Just be sure and try any thing you buy to make sure it works. An extra pump is a must for any pond. It is great if your pump suddenly gives up on you, and helpful to pump out some water so you can do a partial water change.

Happy ponding!


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RE: Rehabbing a pond -- what next?!?!

Smart to progress in stages, like adding the plants later. Great way to learn. When everything is done at once people often get very confused when something isn't right.

You can also hold off adding fish for at least a few weeks so you can get used to testing water parameters, certain of no leaks, etc. Just makes it all less stressful. You can even add ammonia from the drug store to simulate fish if you like.

I didn't realize your pond was so deep. Looked pretty shallow in the pictures. In that case laying a liner into the existing structure would be find. Building up the low spot would be easy and cheap. I'd only bust it out if you wanted a different shape or size.

In case you want to patch...
The issue with cracked concrete is that it is cracked. That sounds kind of dumb but the cracks tell you something important, the structure is moving. That's most people say they understand but don't really seem to because they go forward like this thing is never going to move again. If it's moved in the past it will move in the future. If it moves in the future there will be new cracks. And movement is a continuous event, even if just from temp changes.

The issue with patches it they aren't strong enough to hold a structure together. So patches don't really solve the problem, they just reduce water loss.

Another issue is many people don't use the right patch material. Regular mortar shrinks when it cures so the patch will still leak, just less. What you really want to use is an expanding hydraulic type product. It looks like mortar but expands as it sets. It's more difficult to work with, but gives you a better chance.

Another issue is most people don't want to prepare the crack correctly, or even at all. A crack has to be wide enough to accept the patch material. Just laying a thin sheet of patch over the top doesn't do much, the material has to be inside the crack. The crack generally has to be opened up more like in this video.

Opening the crack also solves the last issue, getting a good bond. Right now the surface inside the crack and on the pond wall is not clean concrete. It's coated with bio film. If you apply a patch it can only adhere to the bio film which is very weak. Even bare concrete has to be made new because concrete kind of rusts. It reacts with CO2 in the air and water forming a layer on the surface of calcium carbonate. So even without the bio film the concrete still has to be cleaned. This is often done with acid, but grinding works too. So opening the crack with a grinder solves 2 issues.

BTW, the concrete rusting thing is also why concrete becomes watertight and also why concrete doesn't shoot pond water pH up to 12-14.

Rubberized materials don't work well either. They sound good but when a crack happens the rubber is bonded to the concrete surface, so where the crack opens there's only a few molecules of rubber that can stretch. Even a hairline crack will exceed the product's ability. Many new ponds are built using a rubberized coating over concrete and they require a concrete structure that will not crack. Even then these products seem to fail more than I would accept.

Concrete swimming pools (gunite, shot, etc) depend on being strong enough to never crack. They can be lifted on of the ground and rolled down the street and would not crack. Many people think it's some coating on these, but it's really their strength that keeps them together. I think that point is missed by most DIYers.

Concrete pools and ponds do sometimes crack, but it's unusual. And in these cases there is an expectation that there won't be more cracking and so these are patched using hitech products.

That's why I would not try patching. Unless you're just wanting a few more years out of the pond and don't mind the water loss. It's a lot of work to patch correctly.


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RE: Rehabbing a pond -- what next?!?!

If you can--please keep us updated on how things are going. I always wonder what happened next.....


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RE: Rehabbing a pond -- what next?!?!

Ok Frankie: posting updates will probably help keep me on track!

Spent some time shoveling muck and schlepping rocks this week, getting the big pond cleared out. Also measured the head height. 12' -- much less than I would have guessed eye-balling it.

But really, we continued the most important job in the garden: hunting worms...

Pond Pic worm hunters

Going to see if I can get the rest of the big stuff out today and get the power washer going tomorrow.


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RE: Rehabbing a pond -- what next?!?!

There is really no reason what so ever to power wash a pond. Sure you get a little more dirt, but ponds generate dirt. So you might only be removing a week or two worth of dirt. Professional pond cleaners do use power washers because owners like the idea, it sounds professional, etc. But it isn't needed.

More important is to have a on going cleaning routine so you never have to empty the pond and do this again.


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RE: Rehabbing a pond -- what next?!?!

Your pond is going to be amazing! A lot of work... but amazing in the end.

I have a concrete pond too (see the attached link) and I'm in the process of rehabbing it this weekend. You don't say where you are but here in New England concrete ponds can be a real hassle because of the winter freeze/thaw cycles. Last winter was particularly dreadful! At one point I was losing an inch of water per HOUR!!!

When Spring (finally) came and I netted out all of my fish (154 goldies) and drained the pond I expected to find a huge crack but I didn't! The deep end of the pond that had cracked very badly three years ago was absolutely pristine. I attribute that to the application of Sanitred Permaflex and liquid rubber.

The area of water loss was the rocks on the waterfall side that were not properly treated with Permaflex. If I had read and understood the directions three years ago I don't think I would have had any problem this year.

Personally, I don't like liners, especially in ponds that make use of the natural, existing environment. Sanitred is safe for fish and used for animal enclosures in zoos. My mistake was not taking off the UGL Drylock (which didn't work) before I applied the premaflex. I could literally pull off the entire waterfall side of permaflex in a single piece! The permaflex on the other side and the two existent rocks bonded like iron!

Anyway... before you make a decision to add a liner at least check out the Sanitred site. They have photos of a cement pond re-hab and a few other pond projects. Well worth a look: http://www.sanitred.com/WaterFountain.htm

Here is a link that might be useful: My pond (old site!)


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RE: Rehabbing a pond -- what next?!?!

I know there is a lot of fear about concrete and freezing, but the reality is properly built concrete ponds are unaffected by freeze/thaw. There are millions of concrete swimming pools in freezing climates. From Alaska to Vermont, throughout Canada, concrete swimming pools have been in service for many, many years. Cracking is rare and when it does happen the cause is always a problem with the soil or how the structure was made, never from freeze/thaw. Properly built concrete ponds are made using the exact same technique. And in both cases the construction method is exactly the same no matter the climate.

People should be very frightened by poorly built concrete ponds as they are very common and virtually always crack and leak no matter the climate. People in cold climates almost always blame the freeze thaw cycle instead of the real problem...incorrectly built pond. For some reason many people seem to think a inch or two of concrete on some chicken wire is somehow just as good as the 12" thick at the top hugely steel reinforced properly built structures. They aren't.

Trying to put some coating over a poorly built structure is throwing good money after bad. These coatings all rely on a stable substructure. Plus the cost can be rather high compared to alternatives.

If anyone wants the look of concrete or rock for a pond and wants to save around $20-30K I suggest laying EPDM liner first and then a thin coat of concrete or mortared rock over the liner. The look it's almost impossible to tell the difference and you won't have any problems with leaks. Very easy for DIYers.

Rock bottom ponds explained.


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RE: Rehabbing a pond -- what next?!?!

One month later, and we haven't made much progress thanks to some much needed rain. Super thanks to everyone for the good information (both on this and every other thread).

I think I'm going to take it slow. All signs suggest I need to keep learning more about working with concrete. I'm going to try playing with some concrete apart from the pond. The public library is helping me out there with the book I found for inspiration: Nillson's "Concrete Garden Projects." Seems like a good idea to have some test runs with some small, cheap stuff from the hardware store before I pony up (time and money) to get after the big cracks and building up the bottom.

Here is a link that might be useful: Nillson's


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RE: Rehabbing a pond -- what next?!?!

Thanks for following up. We have had little rains almost every day. It has been great for the gardens and the weeds! Today they promised 'no rain' so when things get dry I will be pulling weeds and mowing grass.


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RE: Rehabbing a pond -- what next?!?!

There's also a lot of good info on the web too, but also a lot of bad. Sites that show how swimming pools are made are good too because concrete ponds are made exactly the same way, just a few different devices. These things can be scaled down to smaller sizes some what but that gets into problems because there isn't a lot of info because few people build these. Pool and ponds built with concrete are basically the same in size, so after the engineering was figured out for one it could be repeated over and over. So when you compare the cost for a little extra concrete in a smaller size it seems forth it compare to the risk of failure and loss of the entire project.


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RE: Rehabbing a pond -- what next?!?!

Ow, my back. Spent most of the day knocking out rocks and moving rubble. Clearing things out to shore up the bottom edge of the big pond. I figured out a good rhythm for working with the structural concrete, but boy is it heavy.

I also got the old pump out. I'll be looking for a new one in the next few weeks, but it's clear that the stone work is going to take me while at this rate. But, I'm enjoying the work whatever the result!


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RE: Rehabbing a pond -- what next?!?!

I enjoy the work too. Gives me a chance to just let my mine wander. Good exercise too.


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