Results 21 to 40 of 42
-
16-03-2018, 06:42 PM #21
-
16-03-2018, 07:51 PM #22
I dug a hole and put 2”-3” of gravel in the bottom then placed 450mm diameter man hole inspection chamber in the hole. Depending how deep the hole is you can place more chambers on top of each other (they fit together) to make it up to ground level and the put a manhole cover on top. Once they are in place you can back fill the hole around the chamber. They are available from builders merchants and cost about £10 each. The ground around my pond is sloped so part of my pond is about 3ft above ground so at that point my “well” is about 4.5ft bellow ground.
I used 3 chambers on top of each other with a manhole on the top which is out of sight under a gravel path.
-
16-03-2018, 08:13 PM #23
-
16-03-2018, 08:50 PM #24
Rog has the correct idea, building a sump that is outside the footprint of the construction is common practice when building swimming pools as I explained earlier.
Pool builders usually dig a "trench" in the wall as the hole is being dug and use an appropriate length 150 mm pipe so that a submersible pump (with a top outlet) can be dropped in to keep the hole drained while construction proceeds and also if the ground water needs to be drained if emptying is ever necessary. That's cheap but Roger's idea is equally valid especially if you have a side output pump and/or want to use the flow switch.
Whichever method you use, do it as near as practical to where the water is entering the hole.
-
16-03-2018, 09:01 PM #25
-
17-03-2018, 03:05 PM #26
That may be too far away to be effective at dewatering the ground around the pond unless you're prepared to dig much deeper than the pond. The further away you dig the dewatering shaft from an area you want to drain, the less it will drain that area. That's why professional hole diggers, like swimming pool builders, usually install the drainage pipe alongside the excavation as they dig it because that makes it most effective at dewatering the ground and it's also inexpensive.
You can't go back and do that so, as I see it, you have two choices. Either wait until the ground water subsides and the shell dries naturally or bite the bullet and install a drainage point. The first is the easy option but you will have to wait before you can proceed and you may have a problem if you need to drain the pond and the ground water level is high enough to cause the fibreglass to lift.
I've Googled a couple of pictures to show how ground water levels vary. The first is a well which is similar to what you will have if you dig a drainage point away from the pond. The second shows a good strategy for anyone who wants to dig a pond where ground water becomes a problem, just "trench" out one or more walls and push in a 150 mm pipe or use Roger's method of going deeper and wider into the wall as you go so that you can stack drain collars.
-
17-03-2018, 03:12 PM #27
-
17-03-2018, 03:59 PM #28
Membranes or painted waterproof finishes won't work because the external pressure of the ground water will cause them to lift. You can obviously tank the pond shell with a tanking slurry or render the walls with a waterproof cement but there is one problem with that which is rare but happens occasionally so I'd better mention it.
If you make a waterproof structure such as a pond in the ground and ground water builds around it then, when it's empty, it will try to float. The weight of the pond will oppose any lift from the outside water but, trust me, it does happen.
I've seen a 32 ft concrete swimming pool that lifted 4 inches overnight when it was left empty (ready to be tiled the following day) and it rained heavily during the night. Ground water hadn't been a problem during construction but, in just a few hours, it had obviously risen enough to make the pool float out of the ground. The ground was immediately dewatered but, due to soil disturbance, it only sunk back by 2 inches.
As I said, that is rare but I thought I'd better mention it in case you tank the pond and it floats away down the garden in the April showers.
-
17-03-2018, 04:05 PM #29
-
17-03-2018, 04:13 PM #30
That won't dewater the ground around the pond. If, for example, the ground water level is 0.5 metres above the floor level, the floor and the walls will be saturated to that level and the walls above it will be wet. Once you remove the liner, the ground water will start to seep into the pond.
-
17-03-2018, 04:14 PM #31
-
17-03-2018, 04:37 PM #32
A fibreglass finish needs to be applied to dry surfaces but, as I said in my earlier posts, it will lift if the pond is empty while ground water is present which is why a method of dewatering the ground is desirable in case you need to drain the pond or lower the water level below that of the ground water outside it.
If the pond is full of water the pressure or weight of it will keep a liner or fibreglass pressed firmly against the walls and floor provided it is filled to a higher level than the ground water outside it.
If that isn't easy to understand, try it for yourself. take a colander or small bucket with a hole in it and put a piece of bin bag plastic in it then fill it with water. The water will keep the "liner/fibreglass finish" in your miniature "pond" flat against the walls BUT....
If you now slowly lower it into a bigger bucket of water the plastic will stay tight against its walls until the level of water outside is equal to or greater than the water level inside when the plastic will float away from the colander/leaky bucket.
-
Scamp Thanked / Liked this Post
-
17-03-2018, 04:40 PM #33
Thanks for your help with this
I am just trying to think of any ways that I can get the pond dry ready to be glassed as its been nearly 2 years to get to this point and every time I have been ready to have it glassed I could not get anyone to do it
Managed to get ken booked for April but it’s not looking good
Sent from my iPhone using Tapatalk
-
17-03-2018, 05:12 PM #34
Having spent over thirty years in the swimming pool trade where ground water is a frequent problem I feel sympathy for you. Of the several floating pools that I've heard of I've only personally witnessed one concrete pool float but I couldn't even begin to estimate how many times I've seen liners or flexible solid finishes float away from the floors and walls.
As I said, I only see two options. Either bite the bullet and provide dewatering arrangements which will allow you to proceed quickly and allow you to dewater the ground as a precaution if you want to empty the pond. Or wait for it to dry which it will do if the ground water was once low enough not to have caused seepage into the hole while the pond was being built. If ground water has always been seeping into the hole, I'm afraid it's probable that it will always continue to be a problem. I hope that doesn't sound flippant, it isn't meant to.
-
17-03-2018, 05:16 PM #35
-
17-03-2018, 06:59 PM #36
Not sure about being 15ft away from your pond but if you dig a well like mine and leave a pump in the bottom it will pump out water every time the ground water rises into it. Is your pond a raised pond or completely in the ground (how deep would you have to dig a well).
-
17-03-2018, 07:01 PM #37
-
18-03-2018, 01:54 AM #38
So come on, get your spade out, you could easily dig a hole 3ft - 4ft deep and stick a pump in the bottom. After a couple of days of doing just that, my pond excavation drained and I was able to continue with the pond build without it continuously filling up with water.
-
18-03-2018, 02:35 PM #39
I was actually thinking of using a membrane in the hole then lay the foundations.
Build up the sides and then fold the membrane over the block higher than the ground and continue to lay on top..
Will the membrane help at all..
Plus when the celotex is adhered to the inside of the block work before glassing will the dampness lift the celotex from the block work......You get what you pay for...
https://www.koiforum.uk/water-treatme...y-easypod.html
https://www.koiforum.uk/water-treatme...tom-drain.html
-
18-03-2018, 02:37 PM #40
Aquaforte Dm vario 20000 pumps
Still for sale. Postage available for cost Sent from my SM-S901B using Tapatalk