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Thread: Dual Main Drains Question

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    Dual Main Drains Question

    What is the advantage of running a dual main drain setup as opposed to a singular? Is it to mitigate the risk of suction in the event someone were to sit on or get their hair stuck in the drain? I know that kids are instinctively drawn to differences in structure/protrusions in the walls and floors. (I am aware that most main drain covers are supposed to be anti-trapping as well...) That is what I had assumed and been led to believe...

    My future pool builder is a strong advocate of dual main drains. I want to make sure this is right for me. He plans on installing four returns and one skimmer in conjunction w/ the dual main drains. How far apart, center to center should the dual main drains be for optimal safety?

    I am aware that main drains are not explicitly necessary, but I do not know enough about pool plumbing to properly set things up on just the skimmer(s) and returns.

    A search yielded some explanation, but all the links to supporting texts/articles were broken. Thanks for your help...

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    Mod Squad Bama Rambler's Avatar
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    Re: Dual Main Drains Question

    Dual main drains plumbed together is strictly for safety. The drains should be no closer than 3' center to center.

    If you just have a single main drain, it's imperative that you have a SVRS system. And it should be tested on a regular basis.
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    Re: Dual Main Drains Question

    I would recommend dual main drains. I would also want at least two skimmers, each plumbed back to the equipment pad on its own 2-inch line.

    What size and shape will the pool be?

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    Re: Dual Main Drains Question

    In re-doing my pool recently I had the main drain split into two. My PB did this automatically, and I figured it was mandatory from what i've read.

    When the inspector came to give us the pre-plaster inspection he said, "oh it's good to split them". I said isn't it the law? His reply was that our city used to require it for residential pools but they've gone back and re-read the code, and it only applies to commercial pools.

    The reasoning for the dual main drains is that under the right circumstances it is possible for someone to create a seal with their body across the opening and becoming stuck. By splitting the drains off the same common line, you could completely block one with your body and not become stuck because the other drain would just draw in the water.
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    Re: Dual Main Drains Question

    The pool will be a 17x35 shotcrete pool, modified geometric rectangle, with a 7' octagon spa overflowing into the pool. I failed to ask the pool builder about the main drain system for the spa, should this be duals as well?

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    Charlie_R's Avatar
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    Re: Dual Main Drains Question

    Will you have 3' between drains?

    Will it be valved to exclude all other drains and skimmers?
    15'x48" 4500 gallon Intex pool, buried 1.5 ft. Pac-Fab Dynamo 3/4 hp pump. Hayward S180T sand filter, bought used. Taylor K-2006 test kit. Rocket mass heater based wood fired pool heater.

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    Mod Squad Bama Rambler's Avatar
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    Re: Dual Main Drains Question

    Yes, the spa should be duals as well.
    Dave J. TFP Moderator
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    Re: Dual Main Drains Question

    Quote Originally Posted by JamesW
    I would also want at least two skimmers, each plumbed back to the equipment pad on its own 2-inch line.
    Just wanted to make sure you didn't gloss over this comment. I've seen so many renovation threads, or leak solving broken pipe threads that i would want and independent line run to basically everything. That way, in 20 years when someone has a problem, you can shut down the issue and the pool still work.
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    Re: Dual Main Drains Question

    I talked with the pool builder today. He installs the two main drains for the pool 36'' apart, center to center, which is consistent with what I am reading here is the right way to do it. He runs them on their own independent line. He runs everything on at least 2'' piping. The spa will have a dual main drain system as well.

    I don't know that everything else is run on its own independent line, however. I may ask him how much extra he wants for that... I have chosen paver decking for its appearance, increased resistance to earth movement, and ease of removal/reinstallation in event of a leak somewhere decades down the road. To me, this offsets the high labor cost for initial installation.

    The pump will be a variable hayward pump, ecostar svrs to be exact. He installs four returns in the pool, standard. I need to double check with him if he loops the returns in the pool for equalized pressure. I know this isn't as important in the pool as the spa, but I would still rather have it done this way for both the pool and the spa.

    I also already made sure that he plumbs properly for the use of a Polaris.

    He said he typically only installs one skimmer. What is the benefit of another? This pool will be screened in, if that makes any sort of difference...

    Lastly, the equipment plumbing run will be a very minimal distance from the pool/spa, with the equipment being located just outside of the screen enclosure.

    The electrical run to the breaker box will be a bit longer, as the breaker box is located inside the garage, at roughly slightly past the center of the wall on the left adjacent side of where the current patio is/beginning point of the pool screen enclosure. Thanks for all of your help, everyone. I'm open to listening to any/all suggestions for modifications/improvements.

    -Jon

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    Re: Dual Main Drains Question

    He said he typically only installs one skimmer. What is the benefit of another?
    What size is your pool?
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    Re: Dual Main Drains Question

    The pool will be 17x35, modified geometric rectangle.

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    tcat's Avatar
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    Re: Dual Main Drains Question

    I have one skimmer, wished I had 2... so I bought a Poolskim. 2 skimmers is nice since wind is always changing direction, have one at opposite ends helps keep the surface clean.
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    Re: Dual Main Drains Question

    I like two skimmers for several reasons. One is the wind, as mentioned by tcat. If the wind tends to blow debris away from the one skimmer, then you get more debris that is not being skimmed. Having two skimmers helps keep the pool cleaner.

    Your pool is not that large, and being screened in makes the use of one skimmer probably OK, but I would still want two.

    Two skimmers would also help if you had a situation where you wanted a faster turnover of the water due to high bather load etc. Your pump can move quite a bit of water, and I would want that higher flow rate to be divided between two skimmers.

    Overall, one skimmer would probably work just fine. But, I tend to like to over-engineer things for the best possible performance.

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    Re: Dual Main Drains Question

    I'm really not fond of main drains. It's not like they work well at keeping the pool clean. The end up getting leaves stuck to them. I'd personally rather have multiple skimmers over any main drains. Having the main drains spaced apart reduces the change of entrapment but that still doesn't compare to having NO main drains to get stuck to.
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    Re: Dual Main Drains Question

    Funny you mention that X-Pertpool, the builder I am leaning towards insists on NO Main Drains, another says it is critical. Everything I have read says they are NOT critical and more and more PB's are going away from installing them.

    I was thinking the PB I like might have been just trying to save money, but I am thinking he is not at this point.
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    Re: Dual Main Drains Question

    Main drains do tend to fail more often than other parts of the pool. They are also certainly not essential, as many vinyl liner pools do not have them. Still, I like having a main drain. They make it much simpler to get good water circulation in the deep end and they prevent the pump from losing prime (and possibly destroying it's self) when the skimmer(s) get blocked with leaves in the fall.
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    Re: Dual Main Drains Question

    I too am not a big fan of main drains although I have them in my own pool. To me they are more of a liability than a benefit and they are only good for a little circulation improvement that is better served by deep returns. Too often people try to use them to clean up their pool with devastating results. Also, there are many on this and other forums that were forced to cap off their main drains due to leaks since they are very difficult and expensive to fix. So if I had to do it all over again, I would skip the main drains and just use deep end returns instead.

    As for blocked skimmer protection, I think a wall port is a much better way to go:

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    Re: Dual Main Drains Question

    Thanks for all of the input, guys. I really appreciate it, as I am learning a lot of material of this site, both by my inquiries, and reading the past threads of others. I failed to mention that I will NOT have an in-floor cleaning system installed, as the general consensus I have read seems to be that its level of cleaning contribution/benefit does not equal to its financial cost. I am aware of the pitfalls that overutilization of the main drain(s) to clean with can cause.

    I am going to use this builder, for certain. He seems to be the best guy in the area. He does NOT sub out any of the work except the screen enclosure installation, which is not itself directly related to the pool construction.

    I am going to talk to him about a second skimmer. I will go with the dual main drains system he prefers, and absolutely minimize direct usage of the main drains.

    Any other comments/suggestions?

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    Re: Dual Main Drains Question

    If I were to go with two skimmers, how would they be installed? One on either side of the pool, directly across from each other, or perhaps staggered some other way? Pics of y'alls setups or some sort of diagram would help me visualize this better... I just want to be clear on what to instruct the builder on what to do in his planning for the pool, thanks all.

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    Re: Dual Main Drains Question

    On another note, should I do a light in the spa? The builder said he very rarely has someone that requests one, and only has actually installed a handful of spa lights over the past thirty years he has been in business.

    His logic is that most people want more privacy in the spa, and the lighting would detract from that objective.

    I trust this guy's judgement/expert opinion, but I want to hear what you guys have to say... I think I remember that as a kid in my parent's house, they had the spa lit.

    But I have never looked at it from the privacy perspective the builder is. I was personally thinking to have each of the two lights on their own switch, that way they can be operated independently of one another. I don't really mind spending the trivial extra money during a pool build on another light, and not using it much if I don't like it being on. However, in the event I do not install one, and later desire one, I am SOL.

    If it matters much the lights will be either the hayward LED universal colorlogic, or the hayward universal crystalogic.

    I guess I just wanted to hear y'alls opinions, experiences, and pictures of spa light setups.

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