I’m constructing a limestone-faced backyard above-ground pool/fountain with a fiberglas pool liner. The fiberglas liner is expensive (93″ diameter) and has to be drilled at the bottom for a 2″ drain pipe and 2″ stilling pipe (both PVC).
The trick is to figure out how to precisely locate the two drain holes from above with the pool liner in place. It’s nearly impossible to do it by measuring due to irregularity of the exact placement and of the liner profile.
Here’s what I was thinking – any better ideas?
– Stub both 2″ lines up to bottom of pool level.
– Take 2″ diameter pvc caps and use a forstner bit to drill shallow recesses in the cap.
– Glue rare earth magnets in the recesses, cap the pipes and set pool liner in place.
– ‘Find’ the centers from above with a second set of rare earth magnets – mark for hole saw drilling.
Thanks in advance if you can come up with a better way.
Edited 9/28/2009 12:43 am ET by Jeff_Clarke
Replies
Sounds as good a way as I could imagine.
Slightly simpler than "lipsticking" the stubs, and seting the liner up, and pressing down to get the lipstick to come off on the bottom of the liner.
Also easier than a wooden plug in the stubs with a nice sharp finishing nail poking out to mark the liner (which needs a good rap from a dead-blow; and is hugely dependant on getting the plug and the marking scribe very concentric to the stub).
Now, you also can just get a hole somewhere in the 2" ID of the stubs, you can, sometimes "rotozip" to hit the exact bore dimensions, but, that can be fussy if you need to fit to the O.D. of the stubs, rather than nipple through the liner.
sounds good. I was going to say get a metal cap and then use a magnet
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Sounds ok if the fiberglass isn't too thick. Don't glue the elbows below the stub out until after the holes are drilled. That way, you have a little wiggle room to adust if the holes aren't dead nuts.
Jeff, without the liner, take a 2x4 and lay it across the opening so one edge is plumb above both pipe centers. Using a plumb, mark both centers on the edge of the 2x4. Now mark the 2x4 at both ends where it is resting, so it can be removed and replaced in the exact same spot.
Replace your pool, then the 2x4 and plumb down your two marks.
Rich
That's an interesting idea, except that the 'hanging bar' should really be left in place and would have to be 4' or better above the layout - but so what?
Hmmmm
Edited 9/28/2009 10:12 am ET by Jeff_Clarke
**UPDATE**
Using two 36-lb pull neodymium magnets mounted in drainage fittings that put them at the exact centers of the two drain hole locations below the pool allowed for EXACT blind location of the holes from above - the magnets 'jumped' to concentric locations over the ones below through the +/- 1/4" fiberglass and the holes were subsequently drilled to within +/- 1/32"
Pool was glued down - two 2" fittings over two 2" pvc pipe stubs simultaneously with Hercules slow-setting cement.
Jeff
Jeff: The secret to your success is tied up in three words: "36 lb pull" Anything short of that would have courted disaster. Congrats & good thinking!DonDon Reinhard
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