New 18x36 pool with no main drain?

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Donette
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My Pool: 18 x 36 free form vinyl
Location: Ky

New 18x36 pool with no main drain?

Postby Donette » Mon 09 Nov, 2009 00:41

We are having a new 18X36 free form vinyl pool installed. Contract states two main drains. Installer said he did not put in main drains because the pool was only 41/2feet all over and he felt like the two returns and the skimmer would keep it clean. And we would not have to worry about entrapment. The liner is in with a little water. Should we make him install them or is he right??


Slo Jo

New 18x36 pool with no main drain?

Postby Slo Jo » Mon 09 Nov, 2009 06:59

Contract states two main drains.


I think regardless of the necessity you should insist on the terms of the contract being fulfilled. The company felt it necessary when working out the quote and added it in. They added in the cost too. There should be no "out" for them now.

If they feel main drains are not required that brings their marketing/ sales practices into question.

If I bought an air-conditioned car and was presented with no a/c on account of the mild climate I live in, I would not accept it!

That apart, I would not like to own a pool that didn't have a main drain.

Slo Jo
Donette
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My Pool: 18 x 36 free form vinyl
Location: Ky

New 18x36 pool with no main drain?

Postby Donette » Mon 09 Nov, 2009 08:03

Thanks slo Jo for your reply. Was researching it on the Internet and found that one pool compony in Florida installs pools with out main drains. I do have two children and my main concern is their safety. The idea of not worrying about entrapment sounds great. I'm just wondering if the pool will stay just as clean without the 2 main drains. Thanks.
czechmate
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New 18x36 pool with no main drain?

Postby czechmate » Mon 09 Nov, 2009 21:34

Donette wrote:Thanks slo Jo for your reply. Was researching it on the Internet and found that one pool compony in Florida installs pools with out main drains. I do have two children and my main concern is their safety. The idea of not worrying about entrapment sounds great. I'm just wondering if the pool will stay just as clean without the 2 main drains. Thanks.


Do yourself a favor and have them fulfill the original specs!!
Most of the stuff, that enters the pool will eventually end up on the bottom. The main drain will create an effect of flushing, once the rotation of body of water is started with inlets. Skimmer is for top debris only. You will have to manually vacuum bottom on regular basis to get rid of all that stuff that main drain will get with a little help of bottom brush lite sweep. Another often forgotten fact is, that due to natural motion of body of water in this scenario, you will be cleaning clean water since the skimmer will suck in the water supplied by inlets and dirty water will lay almost undisturbed on the bottom!
Dust, dirt, grass clippings, bugs,little worms small parts of leaves,hair etc, etc.
And remember, as soon as some of the organics start to decompose, they start consuming you costly chlorine.
As far as the entrapment, there are several covers on the market that are specifically designed to protect kids. Never mind, that naturally it is very hard to keep human body at the bottom without extra weight, due to it's specific buoyancy.
Only recently these things came to market. I do not believe, that 1 hp motor can hold a child under water against the physics of the weight of its displacement pushing it up! And you may not even need 1HP.
czechmate
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My Pool: 16 x 32 gunite21000 gal., Diamond Brite Blue, Swimquip XL pump, DE36
Location: Texas

New 18x36 pool with no main drain?

Postby czechmate » Mon 09 Nov, 2009 21:45

Donette,

I am sorry that I completely overlooked the size of you pool.
At 18 x 36 feet the two main drains are an absolute necessity!
All this contractors talk is nothing more tan B.S.
What is true is that he is saving lot of money by cutting this crucial corner!
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mas985
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New 18x36 pool with no main drain?

Postby mas985 » Tue 10 Nov, 2009 12:01

The primary purpose of a main drain is for better chemical and heat circulation in deeper pools. The suction in a typical main drain pair is not really sufficient to suck in any debris except for a small area around the drain so they are not so useful for keeping the entire bottom clean. Without in-floor return heads, there is no way to push debris towards the main drain so either way, you will need a pool cleaner of some sort to keep the bottom clean. A cleaner should also help with the redistribution of the water. Also, for shallow pools such as yours, main drains are much less important and are frequently left out of the build since some of the returns can be installed lower or pointed downward to compensate. So as long as you have enough returns for proper circulation, it shouldn't be a problem. Still, it was in the contract so they should compensate you.
Mark
Hydraulics 101 ; Pump and Pool Spreadsheets ; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, Solar Panels, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
czechmate
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New 18x36 pool with no main drain?

Postby czechmate » Tue 10 Nov, 2009 12:36

mas985 wrote:The primary purpose of a main drain is for better chemical and heat circulation in deeper pools. The suction in a typical main drain pair is not really sufficient to suck in any debris except for a small area around the drain so they are not so useful for keeping the entire bottom clean. Without in-floor return heads, there is no way to push debris towards the main drain so either way, you will need a pool cleaner of some sort to keep the bottom clean. A cleaner should also help with the redistribution of the water. Also, for shallow pools such as yours, main drains are much less important and are frequently left out of the build since some of the returns can be installed lower or pointed downward to compensate. So as long as you have enough returns for proper circulation, it shouldn't be a problem. Still, it was in the contract so they should compensate you.


You could not be further from the truth!
Please, next time support your subjective opinion wit some physics.
1. The return valve can be switched to bottom return only.
2. You can partially block the skimmer return with a 3" puck for the 3-4 hrs of the filter run.
3. Bottom drain may be closer to the pump with shorter return line and have a more suction due to shorter restriction and water pressure of extra depth.
3.Without a bottom drain you not filtering bottom water.
4. Using a Polaris to clean bottom, you using already clean water from the filter to disturb the bottom dirty water by throwing if in every direction. That is a solution?
I could go on and on.
Obviously your knowledge of pool construction and pool equipment is lacking basic substance.
In a construction it is called physics.
Sorry if I was little harsh, but do not give advise that concerns someones pocketbook, if you do not qualify!!
RiverPoolsMarc
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New 18x36 pool with no main drain?

Postby RiverPoolsMarc » Tue 10 Nov, 2009 13:42

mas985 wrote:The primary purpose of a main drain is for better chemical and heat circulation in deeper pools. The suction in a typical main drain pair is not really sufficient to suck in any debris except for a small area around the drain so they are not so useful for keeping the entire bottom clean. Without in-floor return heads, there is no way to push debris towards the main drain so either way, you will need a pool cleaner of some sort to keep the bottom clean. A cleaner should also help with the redistribution of the water. Also, for shallow pools such as yours, main drains are much less important and are frequently left out of the build since some of the returns can be installed lower or pointed downward to compensate. So as long as you have enough returns for proper circulation, it shouldn't be a problem. Still, it was in the contract so they should compensate you.

I agree with Mark in his recommendations here. In reality, most inground pool have no need for main drains to achieve proper circulation. The issue here is not whether the pool will circulate well or not, it's that the contractor made a mistake and should have mentioned this beforehand. If you'e happy with the pool installation, I would just seek a small monitary settlement.
czechmate
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Joined: Sat 16 May, 2009 09:20
My Pool: 16 x 32 gunite21000 gal., Diamond Brite Blue, Swimquip XL pump, DE36
Location: Texas

New 18x36 pool with no main drain?

Postby czechmate » Tue 10 Nov, 2009 15:09

Most inground pools have no need for a main drain?
Really?

So you jackhammer a hole in the bottom through a 12 inches of shot gunite and 5/8 steel rebar to mimmick hydrostatic plug to do a common acid wash or resurfacing wit a new plaster??
The REALITY here, Mr. Knowitall, is not circulation, nor mixing water for it's warm up.
The pump is there to enforce the most efficient way of cleaning and distributing of chemicals.Including ACID.
Do us all here a great favor sir and go to fashion forum.
You obviously know just enough to be dangerous.
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mas985
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New 18x36 pool with no main drain?

Postby mas985 » Tue 10 Nov, 2009 15:47

czechmate,

I will ignore the insults for now and focus on the physics behind my statement. With over my 26 year career as and engineer and three years of college level physics, I think that I may know a little bit about physics too.

First, main drains are not like skimmers, they draw from pretty much all directions so the suction in any one direction is fairly small. If you install a main drain pair and use the anti-vortex covers, each cover splits the flow rate into a 360 degree pattern with 44 inlets each. So each inlet has approximately 1/88th of the total flow rate. If a full speed pump is drawing 88 GPM, that is about 1 GPM for every 8 degrees around each of the main drains. Not very much flow rate and will probably move only the very smallest debris already suspended in the water.

Second, my pool has a 9' deep end and a main drain pair. I can tell you for a fact, the suction is not that great to move much debris even if you isolate the main drain and turn off the skimmers which is not something someone would do on a daily basis. For more than about a foot around the drains, the debris just sits on the bottom and does not move toward the main drains. And with an anti-vortext drain, the leaves just get stuck on the outside of the drain anyway since the holes are only about a 1/2" square each so in general, the drains are not very effective at keeping the bottom clean. I rely upon a suction side cleaner for that.

As for #3, main drains are very useful for deep pools but for a shallow pool, I believe, as well as many builders, that they are optional. After all, have you ever seen a main drain in the shallow end of a residential pool? So if a pool is all shallow end, why would a main drain be needed? It is fairly common practice in pool building to leave out the main drain for pools that do not have a deep end so there are quite a few pools without them. This is especially true with vinyl pools where some builders think the risk of a leak far outweighs the benefit of a main drain. Also, nearly every AG pool that I know of does not have a main drain so they get along just fine without them.

As for #4, a suction cleaner, pressure cleaner or robotic cleaner are all pretty effective at redistribution of pool water so yes, I think that is very effective for chemical and heat distribution. Besides leaves, the suction and robotic cleaners will also filter out very fine dirt.
Mark
Hydraulics 101 ; Pump and Pool Spreadsheets ; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, Solar Panels, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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