Backyard Aquaponics :: View topic - HELP! Poly water tank

To seal the large overflow hole I bought a sheet of thick HDPE from a plastics/perspex wholesaler in Ingleburn (a scrap piece which still cost a lot), and used some stainless steel nuts and bolts to bolt it in place. Used some Roof and Gutter Silicone to help seal it but nothing much really sticks to HDPE so the main waterproofing effect was using plenty of nuts and bolts.

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Fourty bucks.. For not sign ificantly more you could get proper stuff professionally welded..
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The old base will need installation on a hollowed bed so the centre is lower.. ie where the swirling poo will gather.

I consider myself to be pretty practical, but I was not prepared to risk such a critical seal.. :oops:

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Round FT don't have to have sloping bottoms for the solids to collect in the center. If you get the inlets right to create enough swirl the solids will collect in the center even if the bottom is an inverted cone. Ie the solids have to travel up a slop to get to the center.

I appreciate what you're saying BuiDoi. I really do. I'm going to try again today to get in touch with a plastics welder who can do the job without costing an arm and a leg

But it also means I'll have to build a special base to accommodate this "cone" shape

Author:	SydneyChick [ Oct 10th, '15, 09:27 ]
Post subject:	HELP! Poly water tank - How do I plug these holes?
Hi! So we have just cut a 1.4m diameter water tank in half to make two FTs The "Top" of the tank obviously has several holes which were the inlet and overflow for the rainwater tank. Does anyone know what would be the best way to plug these? Thanks in advance! :th

Author:	cookie [ Oct 10th, '15, 09:38 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
you can try getting the pvc pipe to fit that opening.. and then put an end cap on the pvc pipe.. that should work Sent from my SM-N900 using Tapatalk

Author:	Gunagulla [ Oct 10th, '15, 09:39 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
You can buy a PVC bung to fit the overflow, which you will need to glue in with PVC glue. However, you need to be certain that the silicone rubber that's in there around the fitting now is sealed properly, before you are ready to go. It might be worth re-sealing Bigger hole is a bit harder- Steve (Rendang) may have a suggestion for it, as I think he had the same sort of hole to seal.

Author:	rendang [ Oct 11th, '15, 17:25 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
Hi. I used the smaller inlet hole as the outlet for the slo. 90mm stormwater pipe can be glued into the existing fitting to go to the growbeds and on the inside a couple of 90mm stormwater right angle bends and pipe can be used to make an slo, the right angle bend will fit right over the existing fitting, no glue though you want to be able to pull the slo out occasionally for a clean. To seal the large overflow hole I bought a sheet of thick HDPE from a plastics/perspex wholesaler in Ingleburn (a scrap piece which still cost a lot), and used some stainless steel nuts and bolts to bolt it in place. Used some Roof and Gutter Silicone to help seal it but nothing much really sticks to HDPE so the main waterproofing effect was using plenty of nuts and bolts. Also been going to mention only use stainless steel in AP, pretty much every other metal is poisonous to fish. Don't even use rainwater collected from your zincalume shed, zinc kills fish.

Author:	SydneyChick [ Oct 11th, '15, 18:49 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
Thanks Rendang! I immediately thought of doing an SLO to external when I saw the 90mm outlet - but I haven't quite wrapped my head around how that works... Doesn't the SLO pipe need to be in the middle to suck out the fish poop? Is there a good diagram or something somewhere that I'm missing? Regarding my woes with fixing that 29cm hole...There's a fish place near us and they sometimes have damaged poly ponds - would a cut out from one of these be a suitable patch?

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Author:	BuiDoi [ Oct 12th, '15, 05:14 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
.. Having gone through the exact issue, I can only comment that professional repair was my response.. I assume that is a poly tank and poly can be welded.. If you are prepared to take the half to be fixed, then the cost will likely not be that great.. ie.. leaving it for a quiet time.. You are northside, and you may find a plastic fabricator over there, but the one I used was near Bankstown Airport.. PS.. I had planned to make patches and bolt them with sealant, but my fear was that "LEAK" that starts after you have 50 fish in there.. I chickened out.. And... when you plan to use those tanks, be sure to set them up correctly. The old base will need installation on a hollowed bed so the centre is lower.. ie where the swirling poo will gather. The heavily shaped top will be OK but will need some careful sculpting of the bed for support.. And don't forget that a picture is worth a thousand word and actually seeing, is worth tenthousand words.. If you drive over Hurstville way, you are welcome to see what I have .. .

Author:	SydneyChick [ Oct 12th, '15, 09:32 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
rendang wrote: To seal the large overflow hole I bought a sheet of thick HDPE from a plastics/perspex wholesaler in Ingleburn (a scrap piece which still cost a lot), and used some stainless steel nuts and bolts to bolt it in place. Used some Roof and Gutter Silicone to help seal it but nothing much really sticks to HDPE so the main waterproofing effect was using plenty of nuts and bolts. I found a HDPE chopping board on eBay 450mm X 450mm and 13mm thick It's only $40 - do you think that would work or is it the wrong sort of HDPE??

Author:	Gunagulla [ Oct 12th, '15, 16:25 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
It will only reliably work if the face you are putting it on is reasonably flat, and you make yourself a ring gasket from a single piece, or 2 single pieces stacked to better conform, of O-ring type rubber (soft and pliable, but strong), then put lots of SS bolts around it to make sure it seals. Otherwise, get it poly welded. I wouldn't rely on silicone sealant to last for too many years, a good mechanical seal is a far better choice.

Author:	BuiDoi [ Oct 12th, '15, 16:31 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
.. Fourty bucks.. For not sign ificantly more you could get proper stuff professionally welded.. .. .

Author:	SydneyChick [ Oct 12th, '15, 16:42 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
BuiDoi wrote: .. Fourty bucks.. For not sign ificantly more you could get proper stuff professionally welded.. .. . Right now forty dollars is sounding like a bargain. The closest plastics welder I have found so far is in Penrith and even if you take the tank to him his minimum charge is $100

Author:	SydneyChick [ Oct 12th, '15, 17:04 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
Found this rubber sheeting stuff called "Make a Gasket" on eBay. It's only 3mm thick but it comes in a 1m roll so I could make two gaskets or more and lay them on top of each other. If I wanted to be super safe I could just leave them as rubber disks and not even cut out the middles. That way if they slip a little when bolting on the HDPE board, the seal will not be compromised. I think unless I find a plastics welder significantly closer than Penrith, the chopping board and rubber gasket with some silicone for good measure may be the way to go.

Author:	BuiDoi [ Oct 12th, '15, 20:14 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
Then what about Bankstown.. and a top fabricator, who has made many aquaculture systems..?? Filling in the top in your case is not so hard as with mine, where it was a flat top and I wanted minimal unevenness, to collect. The muck. You will have a complete depression for the SLO to work in.. I think the top will perform better than the base.. Remember.. Remember... that near nothing really STICKS to PE.. SO. ANY. MOVEMENT, will crack weak bonds and cause leaks.. the only medium that I was.prepared to consider was MASTIC.. Remember that there will be something like 900mm of head pressure on this seal.. the only way that I would have tried it myself would be to have a complete metal ring to bolt through on the far side, and then you still have to seal MANY bolts.. I consider myself to be pretty practical, but I was not prepared to risk such a critical seal.. .. .

Author:	Stuart Chignell [ Oct 13th, '15, 05:18 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
BuiDoi wrote: .. The old base will need installation on a hollowed bed so the centre is lower.. ie where the swirling poo will gather. Round FT don't have to have sloping bottoms for the solids to collect in the center. If you get the inlets right to create enough swirl the solids will collect in the center even if the bottom is an inverted cone. Ie the solids have to travel up a slop to get to the center.

Author:	SydneyChick [ Oct 13th, '15, 05:47 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
BuiDoi wrote: I consider myself to be pretty practical, but I was not prepared to risk such a critical seal.. .. . I appreciate what you're saying BuiDoi. I really do. I'm going to try again today to get in touch with a plastics welder who can do the job without costing an arm and a leg. But the chopping board and gaskets are plan B. Stuart Chignell wrote: Round FT don't have to have sloping bottoms for the solids to collect in the center. If you get the inlets right to create enough swirl the solids will collect in the center even if the bottom is an inverted cone. Ie the solids have to travel up a slop to get to the center. I think BuiDoi is just saying that since the former top of our rainwater tank rose up to a point sort of, when it's inverted it will slope down to a point which is very handy for solids collection. But it also means I'll have to build a special base to accommodate this "cone" shape

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Author:	BuiDoi [ Oct 13th, '15, 06:10 ]
Post subject:	Re: HELP! Poly water tank - How do I plug these holes?
... Quote: I appreciate what you're saying BuiDoi. I really do. I'm going to try again today to get in touch with a plastics welder who can do the job without costing an arm and a leg My welding job cost about what you were quoted.. he is at Bankstown, and I can give you his number.. and his work is now proven.. and he has material to do the work, BUT, you would have to deliver and pick up in order to keep the cost down.. Quote: But it also means I'll have to build a special base to accommodate this "cone" shape No.. you will have to bury in suitably shaped sand and wash it under to further shape and compact.. I built a shaped base from timber to.cause the central depression .. your depression is inbuilt.. sweet.. .. PETER PS.. I would. Assume. The shed floor is bricks over dirt.. I would remove a circle of bricks and fill with builders sand to give you the shaping.. this would have the advantage of dropping the total height, a little.. ..