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LeChat LeChat
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Turning a WW2 Air Raid Shelter into a Pond... #1
Hello All (particularly 2010)

I have recently purchased a house and have discovered the remains of a WW2 air raid shelter in the back garden.

It's solid concrete, about 6 feet long, 4 feet wide, and 26 inches deep. (390 gallons / 1,474 liters per my math.)

One option would be to remove it, but I think it would be nicer as a pond.

This is a reasonably small garden, and the pond would take up about 1/4 of it, so I am considering making it an integral part of the garden, in the style often seen in New Orleans courtyard gardens.... bricking around it, putting in a small fountain (prob not enough space for this) or more likely a small waterfall.

The pond gets good sun in the afternoon, but I'd describe is as "strong partial" sun.

From what I have read, I don't think this pond is deep enough for carp.

I have spent some time surfing around, reading, and while I've found a lot of information on different types of pumps and filters, but I'd very much appreciate some recommendations of specific brands.

Other relevant information:
The waterfall would probably be max 14inches high maybe 20in wide (I think this is more a matter of aesthetics and I'd probably have to play with it a bit. I can envision the waterfall coming down a series of "steps".)

I would like plants - perhaps a few water lilies
(I need to do some more research on this so please don't beat me up.) I am pretty much open to anything - I'd like a natural look but not an aquatic jungle. I'd like to be to see the fish, too.)

Fish - I am guessing that this will end up being a goldfish pond. That's fine.

I'd also love to get some other wildlife in there, but I guess I'll cross that bridge when I've learned enough to cope with what I have already.

Questions:
1. Liner - Do you think I need one?
The concrete hasn't been touched since 194x - it was painted at one time and the bunker has a hole in the bottom for drainage.... it could be patched. I think I am going to need a liner from a fish-health pov, but if I don't have to have one, that works for me.

2. What kind of pump would you recommend? (A brand / type recommendation would be ideal.)

3. Filter?

4. Do I need a UV light?

5. Is there anything else I need to consider?

Ideally, I'd like to buy equipment that will serve me well over the long run which is also reasonably easy to maintain.

Thank you for your input.
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Re: Turning a WW2 Air Raid Shelter into a Pond... #2
Hi, pictures would be interesting.

By your calculations / vocabulary I take it you are American? but where in the world are you?

In no particular order......

Concrete, believe it or not is NOT 100% waterproof its also not suitable for a fish pond so it needs "protection" be that a pond sealant such as G4, fibre glass or a pond liner. But before you rush out and buy anything you should make sure the "pond" is level. Easiest way is to put a level plank from edge to edge and put a spirit level on it. I shall assume it is level.

For wildlife you could put up a sign similar to

"Space to rent, apply within"

but as yet I have yet to see any creature that can read, so you just leave that aspect of it and wait and see what moves in and calls it home. Although either some steps (No really, decent bricks stacked like stairs) or a ramp from the bottom to the surrounding edge is always good as anything that falls in can now climb out.

Fish need to be able to swim up and down as well as side to side, and at 26 inches deep it is, as you assumed too shallow for koi carp.

You ask do you need a "Filter, a UV and anything else?" I suggest that you read the article I wrote which you can find if you click HERE (Also read the pages it links to. )

Fountain? No reason at all why you can't have a fountain. If anything they are good as they introduce oxygen into the water. (So long as the jet height is not more than 50% of the 2nd shortest pond dimension (4 feet in your case) To see why you may want to look at the video Here

Pumps, that depends on what it is to do. (Its a whole subject on its own) But in very short you will need a Filter pump for your filter, a pump that can run a fountain for....your fountain

You may also like to look at This video

And because I can, you may want to look at This video

I no longer recommend brands of things as this is dependant on your budget, but in short the better the quality the more it costs.

If you have more questions (I am sure you will) then please ask.
Good quality costs. Bear this in mind before you start.

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LeChat LeChat
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Re: Turning a WW2 Air Raid Shelter into a Pond... #3
Hi 2010. Thank you for your response.

You are very perceptive, 2010.... For the avoidance of doubt, though, I am in London.

I will digest and revert with questions, I am sure. (Some of my queries were centered around submerged /pump/ filter/ integrated / separate/ etc. I don't mind doing my homework, but this is all so alien the learning curve is steep and there is no substitute for experience. It feels like this is one of these scenarios where a "This is what you need" type of directive would save a lot of mistakes, no matter how carefully researched. Hopefully you will be able to guide me a bit further.)

For some reason, the system is only allowing my to upload 1 photo at the moment. I'll see if I can double-post with another image as well. The garden is obviously a work in progress, but I think it has a lot of potential.

I think this was an Anderson shelter. They are supposed to be 4 feet deep...which was my hope as we were excavating. However, this one obviously fell far short of that. I can only assume that the digger we either lazy or, more likely, in a hurry.

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LeChat LeChat
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Re: Turning a WW2 Air Raid Shelter into a Pond... #4
Just to elaborate a bit further, this is the sort of effect I am going for...

Lush, verdant...

http://www.gonola.com/images/FQ-Courtyard-lead.jpg

https://assets.hipmunk.com/assets/hote ... bfb448f348477b9e89791.jpg

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Re: Turning a WW2 Air Raid Shelter into a Pond... #5
I would say stay away from an all in one, the reason being when they fail (and they do) you end up changing the whole lot, which costs more money than just changing one part. (Which you can do with separates)

I will tell you from the outset, that you will not get anything like what you see in the pictures you linked to. The reason is the pictures you linked to were built from scratch where as you have a hole you want to make into a beautiful pond.

The "problem" if you will is that when you start from scratch you can allow for things like cables, pipes, boxes, electricity etc so when in design stage you make a room, or a channel or..........to accommodate such "extras"

I am not saying give up, far from it, I am saying its going to be an uphill struggle, will not be cheap, but will be worth it when you have finished.

Lets make a start with the liner.

Assume you have one, and an underlay, what will you put round the top to stop it falling in? or will you make the whole surround a "patio"

Assume you have a waterfall, how will you get the pipe from the pump up to the top? (Like wise the cable) also to build a pond properly it should have an overflow for when it rains too much. (My fountain has a simple overflow that just runs to the flowers, but mine is a raised pool, not sunk, like yours)

Pumps are a subject all to them selves, but in short you want ome that can pump waste up to a filter at the correct rate.
So you want a pump that can turn over your pond once every 4 hours, and be able to pump that water up to the height of your filter. (But you don't know where its going to be yet)

I really would like to see this project become something nice. So I suggest you make a drawing / plans of what exactly you want and you make allowances as suggested earlier.

It may take some time, but don't give up.
Good quality costs. Bear this in mind before you start.

Sorry if my reply is NOT want you want to hear, but what I have said is true.

We can only go by what you type.

A "thank you" costs nothing, but goes a long way.
LeChat LeChat
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  • Posted on: 25/8/2017 7:35
Re: Turning a WW2 Air Raid Shelter into a Pond... #6
Hi there. Thank you for replying. I hadn't been checking in because I have not yet had time to research your earlier note and I didn't expect to find a reply from you.

However, to address some of your questions...

Re:The "problem" if you will is that when you start from scratch you can allow for things like cables, pipes, boxes, electricity etc so when in design stage you make a room, or a channel or..........to accommodate such "extras"

Assume you have a waterfall, how will you get the pipe from the pump up to the top? (Like wise the cable)

Yes, I understand that notion. Where I am sort of lost is that I don't have a full grasp of what's going to be required and what it is going to look like. Necessity is the mother of invention, and I am prepared to improvise around the mechanical requirements. For example, maybe it's not a fountain in the middle (which would be ideal), but waterfall down some sort of steps. How big are pumps? How big are filters? Are they in the water or on land? (I know, it depends!) but I've never seen one in person. Could I disguise them in the "rocks"? I don't know. I have to figure that part out.

As for pipes, I am less worried about that. They won't be hidden, but if they were located at the end under a rock or slate stepped waterfall, it might be possible to camouflage them a bit, or to perhaps introduce some strategically placed "tumbling" type plants....

re the liner... Assume you have one, and an underlay, what will you put round the top to stop it falling in? or will you make the whole surround a "patio"

So, what's funny was that after having shoveled and picked the concrete slabs, old tiles, kettle leads, and other junk out of this pit, I had to bail out the muddy water. I would have bet my life that concrete held water!

The top of this "pond", as you can see, is pretty thick. What you probably can't see well from the pictures is that there is corrugated metal that goes around the outside/perimeter. It's sharp and uneven. I was planning on having all edges of the pond bricked about 3 bricks high (as you can sort of see from the suggestion in the images) so that we could ensure the rough metal edges were covered. This would also prevent any runoff from going in the pond, as well as possibly an unwitting animal.

I am still sort of experimenting with the look of the garden, but I think what I am going to do is to brick (patio) around 2 sides, and leave the other two as a plant beds.

If I have to have a liner (and, apparently, an underlay - this is news - must check on that), one idea could be to lay the liner in the pond, let the edges hang out, and then to build my 3 brick high wall on top of that, thereby securing the edges. I am no mason, that is for sure, so I am not certain this would work ...if one were a giant, you'd be able to lift the brick wall right off the liner... However, this might work. The other thing I don't know about is how often the liner needs to be replaced, because that would factor in... the alternative I guess would be to use some other waterproofing method, but as I just did a gut renovation, I am feeling a bit impecunious, and I'd rather go as cost effectively as I can.

RE also to build a pond properly it should have an overflow

Do I have to? Can I just ensure I don't fill it to the brim to start with? It very rarely seems to truly monsoon.... plus, I'd have a 3 brick "wall" where we could, if necessary, build subtle egress holes on the sides of the wall where the flower beds are. That said, this garden seems to have a drainage problem in general (I am not sure if it's because it's clay or because it apparently was a demolition dumping ground) so I am not sure I want an extra water going in there if I don't have to have it.

So is a lower water level an option?

Also, I noticed that earlier you asked if the pond was level. The bottom is most definitely not level, it has about a 2-3 degree slope. I don't have level, so I am not sure about the top, but it does seem level.... May I ask why this is relevant?

Re So you want a pump that can turn over your pond once every 4 hours, and be able to pump that water up to the height of your filter. (But you don't know where its going to be yet)


What if I just architected for the future and bought a bit more power just so I have the flexibility to accommodate snafus (or changes)? I can't see the waterfall being more than a foot or so high and 1/3 the width of the pond... I'd need to play with this in the context of my 3 brick wall to see what looks appropriate.


Can't I have an underwater filter? Or is it better to have it above ground? My mother had a pond and it was a nightmare to maintain. (So she filled it in....)

Whatever, solution I end up with, it needs to manageable.

I think I need 2 key pieces of information before I can move forward.
1. Can I make a 3 brick wall over the liner?
2. What do I want my waterfall to look like in the context of this 3 brick wall. For example, is it going to come over the wall, or will I have a "break" in the wall to accommodate. I suspect it's going to come over...and I can play around with some rocks / bricks / slate etc until I get the right look. That might dictate the size of the pump and the placement / type of filter. (Is that right?)

Many thanks.

(Phew. Longest post ever!)
LeChat LeChat
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Re: Turning a WW2 Air Raid Shelter into a Pond... #7
PS - Can any of the pipes be flexible?

Also, FWIW, this garden was a total mess when I first got it. Just to give you some context, the "pond" was filled in with slabs of concrete, old tiles, basically everything from a prior renovation and whatever was left over from the initial destruction of the shelter. More tiles, slabs of concrete, rocks, bricks, bottles, were also dumped in the garden.

On top of that, someone had dumped a ton of gravel. (Literally.)

So, basically, the back garden looked like a giant mound of gravel / dirt...until we started trying to get it level and discovered the air raid shelter and all the other debris.

We've removed 1 tip + about 150 rubble bags with more to go. We are still digging. Right now, there are still areas which are higher than the pond-to-be....

I will have the patio done by a mason, but I've been laying down bricks as we've excavated in order to have something to walk on that is not mud....

It's definitely been an adventure.
LeChat LeChat
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Re: Turning a WW2 Air Raid Shelter into a Pond... #8
OK, one last post (triple posting is bad form, I know. Apologies.)

I actually think a fountain would look good in the context of this pond, provided I could get one that is the correct height / width so it would not look ridiculous.

I am sure there is some rule of thumb on this.

So, what if I wanted to go this route? (I'd rather pay less, much less, but think of this by way of illustration.)

https://www.primrose.co.uk/small-pando ... rand=&accessories=&page=3

Or better yet, adapt one of the less expensive options to "overflow" (if this is possible.) I think it could be done with a good application of ingenuity... (I realize it's a standalone fountain...)

This would be ideal, looks wise. (Would need to measure to ensure it looked right & also fit, practically speaking. My gut is I'd need something smaller.)
https://www.primrose.co.uk/2tier-maret ... s=&min=75&max=120&ord=asc

It comes with a pump. It's probably not enough or even appropriate for our needs, so prob have to ditch that....

I think you'd have to build a base / pedestal in the middle of the pond for it to sit upon.

Could some mechanics live in that base?
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Re: Turning a WW2 Air Raid Shelter into a Pond... #9
Pumps and filters come in different sizes, why not find your local aquatics centre and go and look (Just look don't buy yet.)

There is actually calculations for waterfalls, but truth be known most pond owners don't know their is such a calculation and they make do. But the important thing is the right pump turn over rate and head height, but if you have a filter just out side the pond, almost any filter pump should be fine.
People often disguise their filter or just hide it away from the pond. But you should also take into consideration that which ever filter you have you will need to access it. Some forget this, and build all over it, which is fine until they need to access it, then they realise their error.

Concrete on its own is not good for any pond, it has to have a liner or be waterproofed. It will let water out. (Believe it or not. Take a concrete foundation as an example, they lay a "membrane" before the concrete is poured, its to stop damp in the future, and what is damp? its water ) Water sitting at the bottom of a concrete lined hole is not the same as a pond. (Since at the time its a hindrance)

You may think the pond is pretty thick (I hope it is) but all you can see is the top, you do not know how thick any other part of it is, but as its so old, and shows no signs of damage you should be ok.

Liners need and underlay for the same reason a carpet does. Some liners have a 30+ year guarantee but you must use the specified underlay. (Some folk use old carpets or wet newspaper for an underlay, problem is they degrade over time giving no support)

You could indeed have a layer of bricks around the top, take the liner over the first layer then add another layer on top. (Liner sandwich if you will) This way the liner avoids the corrugated steel.

A pond should have an overflow, if you opt for the bricks on the liner put a small pipe in between two bricks, instant overflow. (Similar to what you said, but do secure in a pipe, a short one will do.) A lower water level only makes the pool look not full, so its rarely done.

Regarding level, the bottom is not a problem, some koi ponds the bottom is far from level, it slopes towards a "bottom drain" in your case I was thinking more of the top being level all round.

Regarding a pump, you can always turn a big pump down, you can not turn a small pump up, yes, to get a slightly bigger pump than you need is always a good idea. To go to the largest would be just a waste.

Underwater filters are a big pain
Q. How can you carry out work on an underwater filter if its underwater?

A. You have to bring it out.

Any pond / pool / water feature / fountain will need maintenance (Just because you don't see it being done doesn't mean to say its never done, just not often mentioned) that's why its better to think about it now, on paper you can use a pencil and rub out anything you don't like, can't do that when its built, so make errors and ask questions now.

What the waterfall looks like is up to you. Bear in mind the water needs something to flow through / along so if it comes over the 3 brick wall what will hold the sides up? (Maybe remove a few bricks on layer 3 and put the liner there*?)

FWIW I have about 2 tonnes of gravel (20mm) in my pool. I might even post a picture.

Fountain, no problem. But you have to bear in mind the JW rule. It says that "the height of the jet can not be more than half the the shortest length of the pool" The reason is wind. If the jet is too high and its windy, the wind will blow the jet out side the pool, which will if left un-checked empty the pool. If you want a fountain, why not have a fountain pump in the pool (Mounted on some of those bricks you have) with an appropriate nozzle?

As you pointed out, a standalone fountain needs to be adapted to work in a pool, make one mistake in drilling a hole up the centre (It doesn't have on as it must not leak) and you have wasted money, and as you also said its pump will be of no use if it goes in a pool (Pump now too small) so why not save money and just buy a bigger pump and a nozzle.

There is also the option of lighting you may want to think about.

Flexible pipes, not a problem, so long as the diameter is not too small. Often the biggest pipe is from the filter to the pool or water fall.


Points to note:

* Water will always take the easiest route, so you will need to add some sort of "chute" (All be it short, other wise the water may run back under the liner)

The filter must be on 24/7, where as a fountain and or lights can be switched on / off as and when.

You also need a UV, to keep the water clear.

Ask as many questions as you like / feel you need to. But DON'T give up.
Good quality costs. Bear this in mind before you start.

Sorry if my reply is NOT want you want to hear, but what I have said is true.

We can only go by what you type.

A "thank you" costs nothing, but goes a long way.
2010 2010
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Re: Turning a WW2 Air Raid Shelter into a Pond... #10
LeChat, it's been just over a month since your last post, any progress?
Good quality costs. Bear this in mind before you start.

Sorry if my reply is NOT want you want to hear, but what I have said is true.

We can only go by what you type.

A "thank you" costs nothing, but goes a long way.