Upgrading an older Pool to Dual Main Drains

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minimonster17

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Jul 22, 2013
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Is it realistically possible to upgrade an older, now out of code singular main drain system to a newer one complying w/ new code requirements in FL? You know, having two main drains plumbed 36'' apart... I'm just curious, as my parents are going to do a drain and remodel on their older (early 90's) pool soon.

What would happen if you hit rebar when plumbing the 36'' span? Could cutting a little out compromise floor integrity?

And what are y'alls thoughts on adding auto leveler?
 
mas985 said:
Why would you want to risk causing problems? The main drain doesn't really do much and if you capped it off, you wouldn't notice any difference in water quality. Many builders are now building pools without main drains because of studies like this one:

http://www.poolinspections.com/manuals/drains/pools-without-drains.pdf
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Interesting read. I currently have a main drain in my pool and had thought of ways of eliminating it and only thought of sealing it up. Turning it into a return side fixture would be interesting...
 
JVTrain said:
Interesting read. I currently have a main drain in my pool and had thought of ways of eliminating it and only thought of sealing it up. Turning it into a return side fixture would be interesting...
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Anthony & Sylvan has for years built their pools with reversible main drains. The suggested use is to improve warming. I run it in reverse all the time unless the pool is too hot. (No risk this summer.) Allows max circulation and max skimming force at same time. A&S puts all the returns on the shallow wall, so you need to use the main drain in one direction or the other, in my opinion.

I grew up swimming in a 1946 pool with an uncovered single 4" suction pipe going at full 1hp power 24/7 from the deepest point (10 feet). We didn't even have a skimmer until the 60's. We all knew it was a death trap and stayed away, just like we knew not to play in the traffic. Pool never had a fence either--it was grandfathered by code when they eventually required them. Different times....
 
I suppose if I did plumb the main drain to the return side, I'd likely get very little to zero flow from it due to hydrostatic pressure. Would I then have to worry about little to no circulation through the piping running from the return split to the main drain? Are my assumptions about fluid dynamics off on this? Pretty sure that a drain on the floor of an 8 foot deep pool would get very little actual flow due to hydrostatic pressure against the drain...
 
It doesn't matter how low the return is, it is the same net static head which is 0. When water travels from the pump it goes under ground down to the main drain, it gains head (i.e. pressure) so it has plenty of pressure to push up on the water above it. Net static head for pool to pool is always 0 no matter where the suction is or where the return is. Water seeks its own level.
 
mas985 said:
It doesn't matter how low the return is, it is the same net static head which is 0. When water travels from the pump it goes under ground down to the main drain, it gains head (i.e. pressure) so it has plenty of pressure to push up on the water above it. Net static head for pool to pool is always 0 no matter where the suction is or where the return is. Water seeks its own level.
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Thanks for the clarification. I knew if someone would chime in with a great answer, it'd be you! My chemistry background does not extend much into the realm of water hydraulics so I was very unsure of how this set up would work. It would be interesting to see how the flow rates from my 3 current returns would change and change in skimming action. I wonder what kind of main drain cover would be interesting to play with for water flow. I think I may have a new pool project...
 
An interesting read for sure... I had no idea that a main drain could be repurposed as a return. I am concerned about this pool, because my own kids, age 8, 4, and 2 months swim in it regularly. My 8 year old can dive to the bottom of the pool, and my 4 yr old often plays in the spa w/ the water cold. It also has a main drain... All of these stories of evisceration seriously concern me... Can a main drain of a spa be converted to a return in the same manner w/o screwing up the spa mechanics?

I honestly don't know what I am going to do when my own pool is built. FL code requires dual floor main drains, or a floor main drain with a wall mounted drain. I guess I could repurpose them as returns after final inspection? Thanks to everyone for your responses.
 
Dual main drains that are installed to code eliminate or at least really minimize the risks of entrapment, etc. The only way a dual drain setup can become a hazard is if one becomes completely blocked and is not repaired.

I'd check the codes again to see if they are required or if it has to be dual drain IF a floor drain is installed.
 
According with everything I have read and heard, dual main drains are required in FL. In other words, you cannot go w/o a main drain setup in a FL pool, and be in compliance w/ code. There was supposedly a push several years back by a pool builder to get the state laws changed to permit gunite/shotcrete pools to be built w/o a main drain system, but it failed.
 

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They also make vacuum breaks and pumps with high suction shut offs. You might check to see if those are allowed per code in your area. I am glad the laws have been changed to make pools more safe in this way. When I was about 7 or 8 I did a toothpick off a high dive into the 12 ft end of the local public pool. There were three diving boards with a huge drain under each one. I waited a couple seconds to come up them realized I wasn't going up. I looked down, and I was standing right on the drain, and was stuck. I bent my knees, pushed off hard, and shot back to the surface. Ever since then I have been terrified of drains to the point I wouldn't even swim over them at the surface. Now that I have a pool, and three kids, I wanted to make sure they never had such an experience. When we moved into our house I shut off both skimmers where I was only getting flow from the dual main drains. I swam down there and laid right on top of one, and put my hands all around the other one. I couldn't even tell that there was any flow at all. I feel totally fine with my kids being anywhere in our pool without risking their safety.
 
minimonster17 said:
So basically, the main drain could then be configured solely for drainage of the pool, and not also required for suction/circulation? Am I understanding this correct?
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That is my understanding. But there is really no way for them to police that anyway. As long as there is a port (wall or floor) during the inspection, that is really all that matters. I would go the wall port route since if there is ever and issue with it, as there has been many times on this forum, then a wall port is far easier to fix than a floor main drain.

However, this document says that you can build a pool without a main drain so I am not sure what the current law requires:

http://www.floridabuilding.org/fbc/...mmission_education_poc/359/359-1-MATERIAL.pdf

I would talk to your local building department about it.
 
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