Help with Pool Conversion

[manjy]

Hello All,

I'm presently converting my old (15+ years) Concrete home pool from a skimmer type pool to an overflow type. Pool size is ~35' x 17' and the water will overflow from one of the 17' sides only.

The original pool was also very deep and was about 2' above the ground. We've had the top ~18" cut off which has in effect removed the skimmers, pool inlets, suction point and overflow. The only thing left in the pool is the main drain.

Since we don't have any pool stores and/or good (qualified) pool designers in my area (I live in a small city in India), I'm pretty much doing things myself. While searching for some information I chanced upon this very informative website and would be grateful if someone could help me with the following.

1) How do I calculate the size of the surge /balance tank?
2) I understand from one of the posts here that the main drain should also connect to the surge tank with a float valve. Please post a link to suitable float valve so I have an idea about the type needed. Also, will the main drain still be connected to my filter, as before?
3) The water return to the pool will be via a waterfall type water feature about 8" above the pool in the center of the long side. Would this pose any problems or affect water circulation in any way?
4) I plan on adding an autofill to the pool (to keep it just below overflowing) as well as the surge tank. Is this OK?
5) Since I no longer have a suction point in the pool, how could I incorporate this into the system. Is it ok if this is not under water?

Any other pointers you could give me, would be very helpful and appreciated.

Thanks in advance.

 

[Bama Rambler]

That's a pretty massive project you're undertaking!

1) The surge tank needs to be large enough to hold the water in the trough and the excess above the lip if the pump shuts down. So you'll need to figure the volume of the trough and the surface area of the pool times probably 2 to 3mm depth. Then make the tank large enough to handle that plus about 15%.

2) look for cooling tower float valves.

3) it may affect it but it shouldn't be a problem.

4) having it in the pool will be fine but I wouldn't worry about it in the surge tank.

5) the pump will draw from the surge tank, so I don't know what you need a suction port.

Maybe someone with more experience with an overflow pool will help also.

 

[bmoreswim]

My question is just one of shell strength. Doesn't the pool bond beam, since it is usually thicker than the rest of the shell and contains more steel, provide a necessary stronger area around the top of the shell? Do you intend to recreate that in any way around the top? It may not matter at all but that was what came to mind when reading your post.

Good luck with your project! I'm sure it will be a big transformation of your pool.

 

[Patrick_B]

Welcome to the forum!

That is quite a project indeed. Sounds like Bama gave you plenty to work with for a start. Will look forward ot updates on this, and would sure enjoy pictures as it moves along.

 

[manjy]

Thank you for your replies and encouragement.

Bana,

1) I had figured a similar calculation for the surge tank but had computed 2" instead of 2-3mm. Using a depth value of 15mm to be on the + side, I have calculated a tank (taking into account rain, etc.) of 3000 liters (~790 US gallons).
2) The suction port was needed for the Suction sweeper. I guess, I'll route a line from the filter to the bottom of the overflow gutter.
3) Thanks for the tip on the cooling tower float valves. That's perfect and I now know what to look for.

bmoreswim, When I built this pool (again on my own using a book on pool construction), I had cast the entire shell in concrete with 2 layers of steel caging. The floor is about 12" thick and the walls 9" with further waterproofing on the outside. The top 18" have now been cut. This will be finished on top with stone. I don't have a separate beam on top as such.

Brushpup, I will post some pics and update. Thanks.

 

[Casey]

Will be watching this renovation!

 

[manjy]

Here's a diagram I made showing the planned connections. Please let me know if I'm missing anything.

I've added a small recirculation pump to keep the waterfall going when the main filter is off.

I will add a Water Level indicator for the underground Surge Tank for a visual indication. Am also thinking of programming a PLC and making a controller to automate some functions and also safety functions to prevent the motors from running when the levels are lower than normal, etc.

 

[Bama Rambler]

That looks right.

 

[manjy]

The channel and surge/balance tank are being made and I need to calculate the size of the pipe required for the line that goes from the overflow channel to the surge tank. How would I work this out? Will 3" suffice?
My pump is 2.5HP Waterco and pipes from the surge tank and main drain to the filter are 2" Schedule 40.

 

[manjy]

Found this calculator online: http://www.calctool.org/CALC/eng/civil/hazen-williams_g
Using 4" to be on the safe side.

 

[Bama Rambler]

You're doing the right thing using 4" pipe.

 

[manjy]

Some questions on the Overflow Channel:

1) I would ideally like a narrow slot through which the water flows in to the channel but I can't figure out how to have the stone in place so that it can be opened for cleaning the channel. Are there any designs available online for the overflow edge?

2) Is there some sort of a pre-filter or basket, etc. that needs to be installed inside the channel?

Thanks.

 

[Bama Rambler]

You could route it so that you could put a cleanout at one end and that should work.

 

[manjy]

Some Photos..

The top 18-20 inches Cut Off. All stone and Tiles removed from pool and surrounding area.


3000 Liter Surge Tank being made in Concrete. The pipe from the Overflow Drain to the tank is 6" and the Overflow from the Surge Tank is 4"


Will post some more photos as work progresses.

 

[manjy]

While the construction work is on, I am getting all the rest of the equipment updated and put together.

I've been using TCCA as my primary Chlorine Source for a a few years, and a few weeks after starting up, I would always end up with a lot of Algae on the walls. Never understood why this was happening with sufficient Chlorine in the water till I read about the Cyanuric Acid effects on this site.

Decided to go the BBB way in future. I was looking at buying the Liquidator but due to the prohibitive freight cost, I only bought the 'HASA Spares Kit with 3/8" Upgrade' which includes everything but the Funnel and the Bucket. from information available online, I've figured that the Bucket is approx. 100 Liters and is about 30" x 15" x 15" in size, which I will buy locally. I would be grateful if someone could please give me the other dimensions that I need as marked in the photo below.

A= Height of Outlet Point from Top
B= Height of Inlet Point from Top
C= Height of Funnel Drop Tube from Bottom
D= Funnel Diameter

Thanks..

 

[Bama Rambler]

Maybe someone will post the actual dimensions, but they're not critical as long as the inlet float is below the top rim when fully closed and there should be about 1" to 2" between the two floats. The funnel mouth diameter isn't important it just needs to be large enough to allow you to pour the bleach into it easily.

 

[manjy]

Thanks. How much Bleach should be put in at one go?

 

[Bama Rambler]

The factory version holds 8 gallons and that's about half full. The other half gets fill with pool water when the pump starts.

 

[manjy]

Hi,
Whats the best way to add a Vacuum point to an existing pool without a skimmer? Is there some kind of box with a Vac-Lock type fitting available which me allow me to place it close to the pool? Thanks.

 

[Bama Rambler]

If you can access the suction line in the overflow channel, you could possibly add it there.