Nasa Hydraulic Study

Kevin Misley January 31, 2011 at 1:03pm

Todd

Just want make a clarification from my previous post.

I agree removing a bottom drain will eliminate suction entrapment from that point. However, removing them does not eliminate any other forms of entrapment. It's not just limited to suction issues. In the early 70's at our local town pool, my older brother got his finger caught in the "grate" cover in the diving section. He was lucky to free himself to tell the story.

Hope you understand my point.

Glad to see you've been going strong since 1993. I have been in this industry since the early 80's.

Keep up the good work!

Todd Shady Captain Chaos said:

Hi Kevin.

I do understand the benefits of using the drain for draining the pools to winterize and running the pump when water is too low but removing submerged suction outlets would eliminate suction entrapment.Believe me..I have been doing this since 1993 and I do think that main drains put in properly will not cause a suction entrapment and are useful but the only 100% way to eliminate it is to remove them.

Kevin Misley said:

The article was in Watershapes.

I have to put in my 2 cents on this though.

There are some that believe there is no use at all for main drains in a swimming pool. I for one disagree.

I'm located in the northeast so our pools are seasonal. When winterized, we have to drain the water level to prevent damage to tile and other components from freezing conditions. Here, we can utilize a pool's drain to drop the water level. Very useful.

In the spring, upon opening some pools we may encounter a real mess to clean up. Manually vacumming dirt, debris and algae from a pool results in a low water condition.With the bottom drains we can continue run the filter despite the water level being below the skimmers. This saves time and speeds up the cleaning process and pleases customers.

I did read the article. Injecting dye and watching it travel through the water. Seemed kind of silly to me. It looked like a leak detection process gone awry.

I think it comes down to the way your pool is plumbing is layed out, the size of the pipe and how many feet of head, the size of the pump and it's location in relation to the pool.

I think the bottom drains are beneficial as they draw water from the lowest point in the pool, which I believe creates a better distribution of chemicals and sends cooler water to the surface creating a more even temperature.

Mark Urban recently passed away. A pioneer in his own right, developed the flow reversal concept sending heated water through bottom drains to create that same effect. I though prefer returning water through dedicated adjustable floor returns. Drawing water through surface skimmers only does exactly that-draws from the surface only. Why not grab water from different points?

I reference to the entrapment issues, the bottom drain has been made out to be the bad guy. Entrapment is not just limited to suction. Anyone could get there fingers caught in a return wall fitting, suction/vac port when not in use, a loose light rim, a ladder, a rope line even an automatic cleaner hose. Who's to say someone can't get their head stuck in skimmer throat?

Most entrapment issues involving bottom drains occur because of, a single suction source, undersized plumbing, too large a pump, defective or fatigued drain covers or a combination of all. Certainly a step in the right direction was standardizing drain covers to meet certain qualifications and flow rate characteristics.

Yes, maybe eliminating a bottom drain will lessen a chance of entrapment. However, doing away with bottom drains will not eliminate it completely.

Todd Shady Captain Chaos January 31, 2011 at 10:55am

Hi Kevin.

I do understand the benefits of using the drain for draining the pools to winterize and running the pump when water is too low but removing submerged suction outlets would eliminate suction entrapment.Believe me..I have been doing this since 1993 and I do think that main drains put in properly will not cause a suction entrapment and are useful but the only 100% way to eliminate it is to remove them.

Kevin Misley said:

The article was in Watershapes.

I have to put in my 2 cents on this though.

There are some that believe there is no use at all for main drains in a swimming pool. I for one disagree.

I'm located in the northeast so our pools are seasonal. When winterized, we have to drain the water level to prevent damage to tile and other components from freezing conditions. Here, we can utilize a pool's drain to drop the water level. Very useful.

In the spring, upon opening some pools we may encounter a real mess to clean up. Manually vacumming dirt, debris and algae from a pool results in a low water condition.With the bottom drains we can continue run the filter despite the water level being below the skimmers. This saves time and speeds up the cleaning process and pleases customers.

I did read the article. Injecting dye and watching it travel through the water. Seemed kind of silly to me. It looked like a leak detection process gone awry.

I think it comes down to the way your pool is plumbing is layed out, the size of the pipe and how many feet of head, the size of the pump and it's location in relation to the pool.

I think the bottom drains are beneficial as they draw water from the lowest point in the pool, which I believe creates a better distribution of chemicals and sends cooler water to the surface creating a more even temperature.

Mark Urban recently passed away. A pioneer in his own right, developed the flow reversal concept sending heated water through bottom drains to create that same effect. I though prefer returning water through dedicated adjustable floor returns. Drawing water through surface skimmers only does exactly that-draws from the surface only. Why not grab water from different points?

I reference to the entrapment issues, the bottom drain has been made out to be the bad guy. Entrapment is not just limited to suction. Anyone could get there fingers caught in a return wall fitting, suction/vac port when not in use, a loose light rim, a ladder, a rope line even an automatic cleaner hose. Who's to say someone can't get their head stuck in skimmer throat?

Most entrapment issues involving bottom drains occur because of, a single suction source, undersized plumbing, too large a pump, defective or fatigued drain covers or a combination of all. Certainly a step in the right direction was standardizing drain covers to meet certain qualifications and flow rate characteristics.

Yes, maybe eliminating a bottom drain will lessen a chance of entrapment. However, doing away with bottom drains will not eliminate it completely.

Todd Shady Captain Chaos January 31, 2011 at 10:49am

That is the case study.The original document was on APSP letterhead.

Richard A. Falk said:

See Drains Don't Suck!, A New Look At Pool Circulation, and Case Study: The Option of Pools without "Main Drains" and pages 30-34 of this online magazine. I couldn't find the specific study you are referring to.

Richard A. Falk January 31, 2011 at 1:10am

See Drains Don't Suck!, A New Look At Pool Circulation, and Case Study: The Option of Pools without "Main Drains" and pages 30-34 of this online magazine. I couldn't find the specific study you are referring to.

Kevin Misley January 30, 2011 at 3:31pm

The article was in Watershapes.

I have to put in my 2 cents on this though.

There are some that believe there is no use at all for main drains in a swimming pool. I for one disagree.

I'm located in the northeast so our pools are seasonal. When winterized, we have to drain the water level to prevent damage to tile and other components from freezing conditions. Here, we can utilize a pool's drain to drop the water level. Very useful.

In the spring, upon opening some pools we may encounter a real mess to clean up. Manually vacumming dirt, debris and algae from a pool results in a low water condition.With the bottom drains we can continue run the filter despite the water level being below the skimmers. This saves time and speeds up the cleaning process and pleases customers.

I did read the article. Injecting dye and watching it travel through the water. Seemed kind of silly to me. It looked like a leak detection process gone awry.

I think it comes down to the way your pool is plumbing is layed out, the size of the pipe and how many feet of head, the size of the pump and it's location in relation to the pool.

I think the bottom drains are beneficial as they draw water from the lowest point in the pool, which I believe creates a better distribution of chemicals and sends cooler water to the surface creating a more even temperature.

Mark Urban recently passed away. A pioneer in his own right, developed the flow reversal concept sending heated water through bottom drains to create that same effect. I though prefer returning water through dedicated adjustable floor returns. Drawing water through surface skimmers only does exactly that-draws from the surface only. Why not grab water from different points?

I reference to the entrapment issues, the bottom drain has been made out to be the bad guy. Entrapment is not just limited to suction. Anyone could get there fingers caught in a return wall fitting, suction/vac port when not in use, a loose light rim, a ladder, a rope line even an automatic cleaner hose. Who's to say someone can't get their head stuck in skimmer throat?

Most entrapment issues involving bottom drains occur because of, a single suction source, undersized plumbing, too large a pump, defective or fatigued drain covers or a combination of all. Certainly a step in the right direction was standardizing drain covers to meet certain qualifications and flow rate characteristics.

Yes, maybe eliminating a bottom drain will lessen a chance of entrapment. However, doing away with bottom drains will not eliminate it completely.

Todd Shady Captain Chaos January 27, 2011 at 3:06pm

I'm not sure of the magazine but I think it was watershapes.The study was published in fluid magazine as well.

APSP did a case study on main drain options in which the articles were referenced.

I found it by searching case study on the APSP web site.

It would probably be your best source to try to convince you DOH to the use of main drains.

The interesting fact is that the VGB act allows for the removal of the drain.The states are the ones that wont adopt it.

Main drains were used for drains when pools were first built and do very little for circulation,if anything.

I think they started getting tied into the circulation system when they started filtering the water instead of draining and filling.

I hope you are successful in your efforts.It upsets me how the most efficient way of eliminating the entrapment hazard was just discarded by the states.

efforts.it

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