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  1. #1

    New pond build questions

    Hi everyone,

    Looking for some advice about building a new pond.

    its going to be 3mx1.2mx1.2m partially in ground 50cm below and 70 above ground.
    1. Can I get away with thermalite 7.3n 100mm blocks or do I need to use the solid 7n 100mm concrete block.
    2. for the concrete base how deep should this be, will be installing a single bottom drain
    3. 3 or 4 inch bottom drain? I was thinking 3 to help sediment build up
    4. Do I need to add anything to the concrete base other than the steel wire stuff?
    5. What should I do regarding damp proof membranes and damp proof course? Both? One or the other?

    thanks in advance.


    Last edited by MrHudson; 28-06-2022 at 12:49 PM.

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  3. #2
    Senior Member Rank = Jussai Twhitenosugar's Avatar
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    Quote Originally Posted by MrHudson View Post
    Hi everyone,

    Looking for some advice about building a new pond.

    its going to be 3mx1.2mx1.2m partially in ground 50cm below and 70 above ground.
    1. Can I get away with thermalite 7.3n 100mm blocks or do I need to use the solid 7n 100mm concrete block.
    2. for the concrete base how deep should this be, will be installing a single bottom drain
    3. 3 or 4 inch bottom drain? I was thinking 3 to help sediment build up
    4. Do I need to add anything to the concrete base other than the steel wire stuff?
    5. What should I do regarding damp proof membranes and damp proof course? Both? One or the other?

    thanks in advance.
    Hi

    You want to go for the solid 7n concrete blocks, laid belly down. The stronger/heavier the blocks, the better as they will take a lot of lateral force from the weight of the water, especially the first few courses.

    When laying blocks, don't forgot to install your pond returns and skimmer as you go. The amount of people who lay the blocks and then have to go back and core drill their walls out after surprises me, to me doing it that way around seems to just add an unnecessary extra amount of effort.

    From memory my base was about 8" deep. I think most tend to go 8" - 10" deep. I used sofit boards as shuttering, as they worked out cheaper than using wood.

    Definitely 4" bottom drain. If you go for 3" it may end up being a bit of a bottle neck on flow and may be a hindrance if you ever want to increase flow in the future. And it's not as though you can quickly upgrade it if 3" turns out to be not big enough. 4" will be needed especially if you have long lengths of pipework or a few bends. Oh and in terms of bends, make sure you go for swept bends where possible.

    In terms of sediment build up. I strongly recommend putting in a purge valve (ball valve, not sliding valve) teed off from the pipe work between bottom drain and filters. At the time I built mine I was thinking it's just an extra cost and not really necessary. But actually I'm so glad I installed it as it's a really good way to flush out the bd pipes and doing so dumps the dirtiest water in the pond to waste quickly, when doing water changes.

    I got 'mix on site' c35 concrete mix and barrowed it in. I asked for plastic fibres to be added, apparently they help reduce cracking, but I have also read they weaken it ever so slightly. Although I'm not sure the fibres are strictly necessary, especially if you reinforce it with steel mesh. In terms of your mesh, make sure you have it over the bd pipe work, as that'll be the thinnest bit of concrete on your base.

    In terms of point 5, I didn't bother with either. But when I dug my pond out it was in gravel that drained away very quickly and nowhere near the water table. If you are digging down into clay or soggy mud or near the water table (I'm guessing most ponds fall into one of those categories), I'd say go for it. But will leave others to advise which is best.

    Hope that helps.

    Sent from my Pixel 4a (5G) using Tapatalk
    13,000L fibreglassed raised pond with window

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  5. #3
    Senior Member Rank = Jussai Spongebob's Avatar
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    Morning Mr Hudson as above plus

    2, Dependent on ground conditions, min 8 inch is a good average. If your on poor ground it will need compacted hardcore first
    4. Fibres unecessary and not required in C35 mix, no point you will have steel reinforcement. Use A142 mesh.
    5. DPC not needed, wont serve any purpose

    Regarding the size are you restricted? Thats only just over 1000 gallons. The depth could also be an issue presuming you are not heating, most issues in koi ponds arise with having small volumes of water. Again with that depth on clay ground youd likely be in the soggy bad bit, firmer ground will be lower.
    Last edited by Spongebob; 29-06-2022 at 08:33 AM.
    Fibreglassed/5000 gals/4.5 m Tunnel/Spindrifter/Twin drums/Bio chambers/Beads/Showers/Remora ASHP

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  7. #4
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    https://www.koiforum.uk/pond-constru...1+build+thread

    Would try and go a bit more than 1.2 wide as that isnt very big mate.
    Mine is 4 x 3 mtrs and 4 ft deep so in my opinion your depth is ok but 5 ft is better.
    Use the heavy blocks,above is my build I used 9 ins hollow blocks dry stacked and unfilled with concrete and rebar.
    I did use a membrane in the base as I was going to fiberglass so I thought it would keep it dry but it ripped a lot.
    Ready mix for the base is the easiest,they mixed the exact amount on site and they barrowed it in so all I did was level.
    Definately rebar in the base think mine was 9 ins.
    John

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  9. #5
    First off thankyou for your reply very kind of you ����

    I’ll take your advice and go with a 4 inch drain

    have contacted a concrete pouring company to pour my base. Only marginally more expensive to buying the raw materials and saves hiring a cement mixer and worrying about getting the mix right and taking all day doing it and tidying up etc etc.

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  11. #6
    Thanks. So I’ll not worry about the fibres either or dpc. 8 inch sub base.

    regarding size this is just for a grow on / QT can’t go more than 3m long, can make it a little wider upto 1.5m max and could also make deeper. Push it to 3x1.5x1.5 but though for the purpose unnecessary.

    filtration will be sufficient and accurate water management etc shouldn’t be a problem.

    I will be heating

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  13. #7
    Ok so I’ll take all your advice, for the extra bit of digging and cost to heat I’ll make the pond slightly larger hahah you all twisted my arm. I’ll do a 9” base with the rebar and a 4” drain with a purge valve using solid concrete block.

    no need for a DPM/DPC

    im sure I’ll have more questions to follow as I go.

    wasn’t planning on putting any returns in just return from a shower filter and where it’s quite small was thinking of leaving out the skimmer line. Thoughts?

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    Senior Member Rank = Jussai Twhitenosugar's Avatar
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    I'd definitely put in an underwater return.

    In the winter, if your only return is a waterfall or blade, it'll seriously chill your water, which is far from ideal if unheated and also really expensive if heated.

    In terms of skimmer, I think it'll depend how much it'll bug you to always have dust and crap floating on the surface.

    My grow-on doesn't have a skimmer but then again it is indoors so not as badly affected.

    Sent from my Pixel 4a (5G) using Tapatalk
    13,000L fibreglassed raised pond with window

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    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    Didnt realise it was your grow on mr H, think that would be a good size.
    As Mr T said I would use a skimmer if outside makes a lot of difference and you could have it valved so as not to pull too much.

    Are you putting the small drum on this grow on?
    John

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  19. #10
    Yeah you’re right, I’ll only regret not putting a skimmer line in. No point mucking aboutC I was going to install a return that’s blocked off just incase I changed my mind on something but yeah it’ll be a shower and in the winter was thinking of building an insulated box cover for it to reduce the heat loss

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  21. #11
    Haha yeah John…….it’s your filter that’ll running it mate.hopefully all goes well fingers crossed

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  23. #12
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    If useing my shower then just put some 45's on the outlets then extend pipe under water and you will be good to go mate.
    John

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  25. #13
    some more questions

    1. Should I use 25mm or 50mm insulation?
    2. Do I put anything on top of the insulation or inbeteeen the boards before fibreglassing to get rid of the joints or do the joints dissappear after multiple coats and rubbing down?

  26. #14
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    Quote Originally Posted by MrHudson View Post
    some more questions

    1. Should I use 25mm or 50mm insulation?
    2. Do I put anything on top of the insulation or inbeteeen the boards before fibreglassing to get rid of the joints or do the joints dissappear after multiple coats and rubbing down?
    Personally Id use 25 mm, nothing goes on top of the insulation, but seal the joints With aluminium tape, job done.
    Fibreglassed/5000 gals/4.5 m Tunnel/Spindrifter/Twin drums/Bio chambers/Beads/Showers/Remora ASHP

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  28. #15
    And how do I fix the boards, use some grip fill or some kind of fixing?

  29. #16
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    I used gripfill.

    They only really need to be kept in place until the fibreglass has cured. Then the fibreglass/weight of the water will keep them in place.

    Sent from my Pixel 4a (5G) using Tapatalk
    13,000L fibreglassed raised pond with window

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  31. #17
    My thoughts exactly����

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  33. #18
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    Where you up to now Brett?
    John

  34. #19
    I haven’t started yet. Digging Monday. Laying slab Wednesday. Bricks Friday/Monday fibreglassing Wednesday/Thursday filters etc weekend fill ���� That’s the plan. I’m sure I’ll still be working on it in 4 week ��

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  36. #20
    Extreme Koi Member Rank = Supreme Champion john1's Avatar
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    You useing a digger then?

    Sounds an interesting plan mate.
    John

 

 
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