5,000 GPD Down the Drain

Jump to latest Follow Reply
Old Guard

Old Guard

In The Industry
Apr 14, 2022
54
Flowood Mississippi
Pool Size
420000
Surface
Plaster
Chlorine
Liquid Chlorine
My biggest pool (420,000 gallons and 6,885 sq. ft. if surface area) is losing almost 5,000 gallons per day. More perplexing, the water is not just vanishing—it is pouring out the end of the pipe it normally exits when we are backwashing or rinsing the filter. I have replaced one 6" butterfly valve that would not close all of the way. I have turned off the circulation pump more than 24 hours ago. Yet the water continues to poor out of the waste pipe. I'm waiting to see where it stops but cannot fathom why it is happening at all.

Suggestions?
 
OG,

Not sure it applies to a pool as big as yours, but I would be looking at whatever valve you change to select between the Filter and Backwash modes.

In smaller pools this is called the Multiport Valve or MPV. They often develop leaks that do exactly what your pool is doing.

Thanks,

Jim R.
 
Old Guard said:
My biggest pool (420,000 gallons and 6,885 sq. ft. if surface area) is losing almost 5,000 gallons per day. More perplexing, the water is not just vanishing—it is pouring out the end of the pipe it normally exits when we are backwashing or rinsing the filter. I have replaced one 6" butterfly valve that would not close all of the way. I have turned off the circulation pump more than 24 hours ago. Yet the water continues to poor out of the waste pipe. I'm waiting to see where it stops but cannot fathom why it is happening at all.

Suggestions?
Click to expand...

It’s a gravity drain situation. The level at which the water exits the filter is lower than the pool’s water level so it will keep draining.

Like @Jimrahbe said, you need to check the backwash valve / multiport valve on your filter as there is a leak there. It will not stop leaking just because you turn off the pump.

Perhaps post some pictures and we can better help.
 
5,000GPD is roughly 3.5GPM. That’s the rate at which a standard water hose operates. That’s a very substantial leak and should be able to be located pretty quick.
 
This pool uses 4 6" butterfly valves to redirect flow. I created this crib sheet to keep me straight on how to do what:

1670795631303.png
In an earlier attempt to fix this problem, I replaced valve 3 which was not closing completely. I am now thinking valve 4 is the culprit. Nonetheless, I find it totally amazing that the water would siphon itself up to a height of probably 5 or 6 feet higher than the level of the pool through the pumproom and out the discharge pipe. The end of the discharge pipe is a good five feet lower than the pool deck.

When I checked at noon today another inch was gone and a gallon was coming out the end of the pipe every minute.
 
This is what the set-up looks like. Valve 2 is in the lower right hand corner. 1 is upper right. 3 upper left. 4 lower left. I believe the pipe that leads to the drain pipe is the vertical one just left of valve 3 and right of valve 4. It disappears into the floor just beyond the bottom of this picture.
 

Attachments

  • Clinton Valves.jpg
    Clinton Valves.jpg
    487.7 KB · Views: 34
Put to a plug in the pipe to stop losing water until you figure out a fix.
 
Siphoning can easily happen as long as the water path and volume in the pipe is continuous and the discharge is at a lower elevation than the source. I have seen rain water capture systems where a 4” pipe collects water from a roof gutter 12ft off the ground, plunges below grade by a foot, runs 50ft across the yard, and then daylights up out of the ground to the top of a collection tank that is 8ft tall. Water will always seek it’s own level so whatever difference in height there is between the surface of the pool and the discharge of the backwash pipe, the water will flow and it doesn’t really matter what the pathway looks like between the two point.

If there is a high point in the pipe between the pool and the discharge, then the flow can be stopped. This is essentially what a Hartford Loop is for. Otherwise, you have to rely on sealed valves to hold the water back.

Sounds like your valves are leaking. You need a qualified plumber to come in there and possibly change out all of the valves or rebuild ones that can be rebuilt.
 
Old Guard said:
>>In an earlier attempt to fix this problem, I replaced valve 3 which was not closing completely. I am now thinking valve 4 is the culprit. <<
Click to expand...
From your description, I agree that it's likely valve #4 that's leaking. Especially since you've already replaced #3.

In filter mode either valve #3 or #4 leaking would cause water to come out the backwash line.
 
  • Like
Reactions: JoyfulNoise

Enjoying this content?

Support TFP with a donation.

Give Support
Right now, if you open valve 3 and open the pump lid and the filter air relief, the flow should stop.

Verify that the water stops.

There are several things I would put on the waste line:

1) A vacuum Breaker.

2) A valve.

3) A site glass.

4) A union so that you can open and verify if it is leaking.
 
Last edited:
  • Like
Reactions: JoyfulNoise
For the sight glass, you can use clear PVC pipe.

This will allow you to see the backwash water to see how effective the backwash is and it allows you to see if the line is leaking.

6" Clear Schedule 40 PVC Pipe - 5 ft.

6" Clear Schedule 40 PVC Pipe - 5 ft. on Sale! Available now at super low prices! No need to buy a full 10 foot stick anymore. Save more when you get all your clear PVC fittings as well!
www.pvcfittingsonline.com www.pvcfittingsonline.com

Note that one review said that the transparency was not good.

1670861330787.png
 
Last edited:
There are several reasons to use a vacuum breaker.

1) To prevent siphoning.

2) To allow the pipe to drain.

3) To prevent water hammer when you close the valves.

100 feet of 6” PVC pipe holds about 150 gallons of water, which weighs about 1,250 pounds.

Based on the pool size of 420,000 gallons, an 8 hour turnover is about 875 GPM.

Based on the fact that the end of the discharge is at least 5 feet below the pool, the flow through 6" pipe will still be about 875 gpm when the pump is off due to the siphon effect.

875 GPM through 6” pipe is about 9.93 feet per second.

1,250 lbs at 9.93 feet per second is about 2.6 kilojoules of kinetic energy or 385.8 lbf s (pound-force seconds) (1716 kg m/s (kilogram meters per second)) of momentum.

All of that kinetic energy and momentum has to be lost as the water abruptly comes to a stop which causes water hammer, which you have probably noticed as a bang as the valve is closed, especially if the valve is closed quickly.

Think about a 150 gallon container of water (1,250 lbs. of water) moving at 10 feet per second hitting a wall and you get an idea about the amount of force that is being put on your pipe and valves if the valve is closed quickly.

Water hammer can damage the valves.

A vacuum breaker will prevent water hammer for the waste line and any associated damage.

You can still get water hammer upstream of the valves, but that can be mitigated by closing the valves slowly.

The vacuum breaker should be able to do about 2 to 3 cubic feet per second (About 900 GPM to 1,350 GPM).

The valves require periodic maintenance and you should have extra valves that you can use to quickly swap out a valve and do maintenance on the old valve.

At a flow of 875 GPM the filter would need to be about 58 square feet of surface area at 15 GPM per square foot.

The diameter of the filter would need to be about 8.6 feet.

The filter looks a little bit small for the pool size.

What is the turnover time required?

What is the flow rate?

What is the filter size?
 
Last edited:
  • Like
Reactions: HermanTX and JoyfulNoise
Wow! Thanks for all of the help!

I didn't go to that pool today. It is a 45-mile round trip, but I will go tomorrow.

By noon tomorrow, the water level should be at or below the bottom of the skimmers. I'll measure the water level in the pool and the flow rate at the end of the discharge pipe.

Next, I will remove valve #4 from the system and just leave a big gap in that 6" flange. I ordered a new, 6" butterfly valve today. Don't know when it will arrive but that does not matter much. Just want to leave a big hole in the system for now.

Then, I'll check the discharge rate again. Hoping for nil.
 
For a vacuum breaker, you can probably just T a line up from the waste line with a regular valve or check valve so that you can introduce air to allow the waste line to drain.

A vacuum breaker is just a check valve, so a Jandy valve would probably work.

I would do a U bend back down and put a 4-way pvc cross on the line so that debris does not get in the line.

The cross is so that you don't have a single point of suction.

Note: Get design approval for any system modifications from a qualified engineer before doing any system modifications.

Changing the plumbing should only be done based on the design of a qualified professional and the work should only be done by a qualified professional.
 
The system seems to be undersized for a 420,000 gallon pool.

Since it is a waste line, you are probably required to have some sort of anti-backflow/anti-siphon device on the waste line.

In addition to a vacuum breaker, you might be required to have a check valve.

In some cases, an air gap is required.

Check your local code to be sure.

Maybe something like this for the vacuum breaker.

The CV is a Jandy check valve.

The pipe can probably be about 1.5" or 2".

Does the system ever bang when the valves are closed?
1670945073087.png
 
Last edited:
1670953006191.png

Per Arizona Administrative Code

R18-5-236. Disposal of Filter Backwash, Wasted Swimming Pool or Spa Water, and Wastewater.

“Filter backwash and wasted swimming pool or spa water shall be discharged into a sanitary sewer through an approved air gap, an approved subsurface disposal system, or by other means that are approved by the Department. “

_______________________________________________________________________________________________________________________________________

454.1.6.5.15 Pool Waste Water Disposal

2020 FBC - Building, 7th edition > 4 Special Detailed Requirements Based on Occupancy and Use > 454 Swimming Pools and Bathing Places (Public and Private) > 454.1 Public Swimming Pools and Bathing Places > 454.1.6 Plumbing Systems > 454.1.6.5 Recirculation and Treatment Systems > 454.1.6.5.15 Pool Waste Water Disposal

Pool waste water shall be discharged through an air gap; disposal shall be to sanitary sewers, storm sewers, drainfields, or by other means, in accordance with local requirements including obtaining all necessary permits.

Disposal of water from pools using D.E. powder shall be accomplished through separation tanks which are equipped with air bleed valves, bottom drain lines, and isolation valves, or through a settling tank with final disposal being acceptable to local authorities.

D.E. separator tanks shall have a capacity as rated by the manufacturer, equal to the square footage of the filter system. All lines shall be sized to handle the expected flow.

There shall not be a direct physical connection between any drain from a pool or recirculation system and a sewer line.

up.codes

Pool Waste Water Disposal | UpCodes

Explore a searchable database of US construction and building code. Code regulations are consolidated by state and city for easier navigation.
up.codes up.codes
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply