Rebar and plumbing... is this right?

jscozzJuly 30, 2012

I have seen countless pictures of pools during construction that show two specific details widely used:

1) Concrete chunks or dobies used to support the rebar instead of metal chairs.

2) Plumbing run on ground surface under rebar, leaving no space between pipe and rebar.

Seems to me that concrete chunks or dobies will create large voids in the gunite shell under the rebar... and that pipe runs will create long voids and weak spots in the gunite.

But I see this in MANY pictures on here and other web sites of pools being built.

I guess my question is, are these as serious issues as I believe they are? It seems like very little work to trench in the main drain line so you get full 3" min gunite under rebar even where the pipe is... and it seems metal chairs should be the same cost or cheaper than blocks. In fact, I thought I saw somewhere on here that someone mentioned that using blocks was a code violation.

I'd appreciate feedback...

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Concrete dobies are what is specified by the ACI for concrete applications for pools and flat work. Metal chairs are to weak to stand up to the crewss stepping on th rebar when they are shooting the pool. Things such as brick, stone etc are not to be used. Brick blocks are not as strong as concrete dobies and they would leave a void. Plumbing pipes are to be a minimum of 3" away from rebar. It it better to bury the pipes under the dirt rather than trying to space rebar off of pipes . Gunite needs to be 3" over rebar and 3" under.

    Bookmark   July 30, 2012 at 2:36AM
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I guess I am running in to "what is best" and "what is practical and standard"...

1) On the pipe issue... the drain pots have side ports that I see most all pool builders tie together two drains with a straight run with tee in the middle and then go to side and up. With the pipe coming directly out the side of the pot there is NO way to make that interconnecting pipe lower than the rebar. In fact, since I requested a 3" rigid PVC drain line, the rebar will sit right on top of the pipe, since that will be the 3" spacing to stone. They ran the pipe to teh side down under the stone, which is good, but I need to fingre out what I want to do with the area between the drains and i have two sets in the deep end, so two 4' sections without gunite under the rebar and direct path for water to get to the rebar. I need to determine what I will do here... I am thinking I should dig out under the pipe for 3" so at least the gunite will flow under the pipe and there will be proper encapsulation of the rebar. Anything else I should do?

2) On the dobie issue... my PB uses pieces of pavers. I have called every masonry supply house around and no-one carries dobies. Many people did not know what a dobie was. Home Depot and Lowes list them on their web site but no store has them. The elusive dobie... I can see the dobie being an exact 3" (not sure what the paver height is), but other than that, they both create a void and probably allow water to penetrate to the rebar, so is there really a structural difference? Is it a code issue or just a "standard" that most pool builders do not follow anyway?

    Bookmark   August 8, 2012 at 11:08PM
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A dobie does not create a void. It is surrounded by concrete and is part of the shell. That's why the code is concrete dobies so it matches what you are shooting the pool shell out of. As far as your situation with the pots. That's why I do not use them. Get rid of the pots and come up directly with the pipe from the bottom of the pool and tee them up underground. I know poolguynj how much you love pots but in this case you can ditch them. Also why the 3
" pipe? Did you or your builder figure out hydraulically what kind of suction you need out of that main drain line? I agree bigger is better but 2.5" should suffice for a secondary suction line.

    Bookmark   August 9, 2012 at 1:13AM
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I had the same concern with my pool build. I insisted that he bury the deep heat returns and main drain lines under the rebar to create a greater void between rebar and ground level/pvc. There was about 6 inches of 3/4 inch stone on the floor of the pool dig-he had to dig a trench in the stone by hand reaching between the rebar to accomplish this. Search under buzz2 and you will see my threads.

    Bookmark   August 9, 2012 at 6:17AM
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They actually did put the main line from the side of the pool under the stone... then it T's up into a line that goes between the pots which are 4' apart. It is that 4' section between the pots that is the only issue. The rebar sits on top of the pipe. There would only be 2-1/2" of gunite on top of the pipe, and only 2" where the rebar is... in and of itself that is not too bad... although I would prefer 3" gunite on top of the rebar like the rest of the pool will have... but my concern is under the pipe... and also that the 6' strip (including the pots) will only have 2-1/2" of gunite. Instead of having them rip out the whole thing and redo it, would it be acceptable to dig 5" under the pipe and ask them to set rebar around the pipe on the bottom (a couple inches off the pipe and 3" off the ground) and then shoot that full of gunite also? Seems to me that would be easier than redoing the plumbing and would probably be a better end result?

    Bookmark   August 9, 2012 at 10:00AM
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You can use concrete bricks and break them in half.

The steel and pvc should not be touching. The best way is to use the bottom port of the main drain pots but since they have already plumbed it from the side ports you can 90 down to bury the pipe.

    Bookmark   August 9, 2012 at 12:16PM
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Aren't concrete bricks only 2-1/2 high?

    Bookmark   August 9, 2012 at 10:45PM
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