Installing additional pumps

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Help Please

Installing additional pumps

Postby Help Please » Sun 31 Jan, 2010 08:08


We have a newly built inground public pool that definitely needs additional pump. The problem is it is now operational and no more suction pipe is available for the new pump. Putting it on a cart is not an option because the suction is exposed and we have to put it on during daytime which is quite dangerous and an ugly sight. Is it possible to tap the suction of the additional pump to the existing pump? Will it destroy the pipeline if you have two pumps operating at the same time for a single suction pipe? Will it not destroy the pumps too? Any brilliant suggestion and advice will be much appreciated.


The Pool Expert

Installing additional pumps

Postby The Pool Expert » Sun 31 Jan, 2010 19:06

If you can provide more details of your system and pool, I will probably be able to help you find a solution.

01) Current pump make, model, horsepower and S.F (Service Factor).
02) Volume of pool in gallons.
03) Make, model and type of filter.
04) Description of all suction plumbing. How many pipes and what size they are.
05) Number of skimmers.
06) Number of main drains.
07) Description of all return lines.
08) Current flow rate.
09) Current filter pressure.
10) Description of the problem you are having.
11) Number of people who use the pool each day. Minimum, maximum and average.
12) Dimensions of the pool. Length, width and depth.
Help Please

Installing additional pumps

Postby Help Please » Mon 01 Feb, 2010 18:35

The pool is an 8 shape at 40m X 25m. Deepest portion is 4 ft with shallow part at 2ft. Shallow portion is only around 1/8 part of the pool. Right now we have 5 sets of 3 hp centrifugal Hayward pumps with 7220 DE filters. During normal season, there is really no problem with our pumps. Water is always crystal clear. But during peak seasons where huge number of people swim, the 5 pumps no matter how often we clean cannot just seem to avoid the water being cloudy. We would operate the pumps up to 18 hours but just cannot catch up the next day and the coming days. We have 100 people using the pool during lean season, but during peak season it reaches 1,300 and even more. A number would swim in the early morning, other groups during lunch time, some in the afternoon, and still a lot during night time. The pipes are 2 inches in diameter. Now just 1 maindrain and 1 skimmer for each of the 5 pumps. I am planning to add 2 more pumps installed on a push cart to be operated during night time. The suction of this is expose. But with the huge number of people during peak season, I must operate the additional pumps during daytime too. I am worried that with the exposed suction it might be dangerous to the public. I have no problem with the return pipe since i can just connect it to the water slides. My problem is where to tap the suction of the new pumps. Is it alright to have 2 units of 3 hp pump in a single 2 in. suction pipe running simultaneously? If ever i have no choice but to install it on a push cart, what design would you suggest for the suction that will not be dangerous to the children?
Thank you again for your assistance.
The Pool Expert

Installing additional pumps

Postby The Pool Expert » Mon 01 Feb, 2010 23:55

What country are you in?
Has this pool been inspected and passed by the Health Department and/or the Building Inspector?

Based on your figures, I calculate that your:

Volume is about 250,000 gallons.
Surface Area is about 10,500 square feet.

Assuming a 3 hour turnover, you should have a flow rate of about 1,400 gallons per minute.
Assuming 1 bather per 20 square feet, you have a maximum bather load of 525 people.
Assuming 1 skimmer per 500 square feet, you should have 21 skimmers.

Assuming (5) 3-H.P pumps at 120 gpm per minute, your actual turnover is 600 gpm. This is less than half of the required flow rate necessary.

You have 1 main drain and 1 skimmer per pump for a total of 5 main drains and 5 skimmers. You should have 16 more skimmers than you have.

Assuming 60 gpm per main drain and 60 gpm per skimmer, your water velocity in your suction lines is about 6 feet per second, that is the maximum allowable velocity. You cannot add any additional flow to the suction.

You should never have only 1 main drain on a suction line. You should always have at least two main drains per suction line. This is very unsafe. Does each pump contain an SVRS (Safety Vacuum Release System)?

Based on the information you have provided, I cannot believe that this pool has passed any type of Building or Health Inspection. It is my opinion that this pool is not safe to operate from a mechanical or sanitation position, and should be shut down immediately until it can be brought into compliance.

As this is a new pool, you need to go back to the builder and ask them to fix this.
The Pool Expert

Installing additional pumps

Postby The Pool Expert » Tue 02 Feb, 2010 01:25

Just to be clear, your pool is 25 meters by 40 meters by about 1 meter average depth, right?

That's 82 feet by 131 feet by an average of 3 feet deep, right?
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Installing additional pumps

Postby Me... » Thu 15 Apr, 2010 21:55

Without spending a lot of time trying to decipher that, I have to agree with The Pool Expert. That pool sounds like a very under equipped pool. A 2" line is actually only good for about 60gpm on a suction as stated and maybe 80-90 on the return side so I doubt you would get 120GPM through those lines. A 3hp pump is way too big and a waste of money. A good 1.5hp would do that.

Figuring you might only get 5 x 90gpm thats only a flowrate of 450 tops, suitable for a pool about half that size maybe.

A problem like this can also be more chemical than mechanical. This is where good Automation and Ozone will be extremely beneficial.

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