theory vs practice - filling a pool

[PoolGate]

So am I correct in these calculations?

Water Pressure = 40psi
Hose Size = 3/4 inch
Hose Length = 25 feet
Flow = 72gpm
Fill time 30,000 gallons = 7 hours

Sounds like not enough! I was told 2-3 days.

What in practice is it taking people to fill their pool from a hose?

 

[blay127]

72 gpm seems way high for a garden hose

 

[wjr75]

Mine takes about 24 hours for 20k gallons using two hoses. Not sure what the water pressure is but it is good.

 

[JoyfulNoise]

Fill a 5 gallon bucket with the hose, that'll tell you the flow rate. Most garden hoses can't do more than 5-6 GPM

 

[Trele6]

So am I correct in these calculations?

Water Pressure = 40psi
Hose Size = 3/4 inch
Hose Length = 25 feet
Flow = 72gpm
Fill time 30,000 gallons = 7 hours

Sounds like not enough! I was told 2-3 days.

What in practice is it taking people to fill their pool from a hose?

Flow of 72GPM sounds WAY high.

 

[Sunnymosmile]

I have a 16,000 gallon pool that we filled earlier this year. Used two hoses and it took two days but our pressure isn't the greatest.

 

[JoyfulNoise]

If you're near a fire hydrant some cities allow pool owners to fill from a hydrant. You have to fill out a form, get a permit and special meter and the fire dept can come and hook you up. You'll fill a lot faster but you'll want to put a shower cap on the end of the fire hose so you don't blast the plaster off your pool.

 

[PoolGate]

I got this from this website calculator for flow.

Garden Hose Flow and Time Calculator

 

[JoyfulNoise]

Just measure it with a bucket, it's a lot easier....

 

[Trele6]

We are having the autofill equipment installed in our pool. Would we be able to use that for initial fill-up also?

 

[JoyfulNoise]

We are having the autofill equipment installed in our pool. Would we be able to use that for initial fill-up also?

Not a good idea. They are very slow. Best bet is just multiple hoses with a rag or empty soda bottle tied to the end to let it float so the metal hose-end doesn't bang against the new plaster.

 

[JoyfulNoise]

Always fill from the deep end and don't allow the water to trickle down a wall or else you'll get stains.

 

[PoolGate]

According to that site, the biggest killer of volume is a longer hose. So going with the max that a standard hose bib will take (3/4") and the shortest hose to your pool (25ft for me) I think that significantly increases flow over a standard 1/2" or 5/8" garden hose that you would pick up from home depot. And with that logic also running from a neighbor is near useless due to the length of hose killing volume. For an initial fill I would even cut the hose to be as short as possible to reach the pool.

What size and length hose is everyone here using?

 

[chiefwej]

More typical flow rate for household garden hose is around 7.5 gpm. An 1.5 fire hose with a good hydrant might flow 75 gpm, but never a garden hose with household pressure. 1.5 hose with pressure boosted by a fire engine only flows around 125 gpm.

(The Chief in chiefwej stands for Fire Chief, 40 years in fire service)

Friction loss is a function of the diameter and length of the hose in relation to the volume. Diameter of the hose is your primary limitation, then comes length secondarily. Pressure at the water source is reduced by the friction loss in the hose, and the final flow is a function of the diameter or the end of the hose and the remaining pressure at the end. Running multiple hoses helps, but won't double flow because pressure will drop so much. Running from a neighbor may be better than a second hose because of that pressure drop. I've run three hoses, but my household pressure drops so low that my other faucets all go down to a trickle.
here is a useful friction loss chart for small diameter hose, like garden hose.


You can see by the chart that it would take 370 psi to push 60 gpm through 100 ft of 3/4 inch hose!

 

[borjis]

I used a 5 gallon bucket to determine my fill time.

Came right in where I thought. (didn't want an over flow while at work) it also
gave me a much more accurate pool volume than the scribbled paperwork indicated
and matched pool math.

 

[CaptainCannonball]

I used my water meter to measure my fill. 10 gallons every 17.3 seconds or 34.7 gpm was enough to fill my pool in less than 10 hours. (20,500gal as measured by our water meter)

That was two 50' 3/4" hoses and a 25' 5/8" hose.

 

[mas985]

I got this from this website calculator for flow.

Garden Hose Flow and Time Calculator

I think there is a major flaw with that calculator. They are assuming that the pressure at the spigot is fixed and it never is. There is head loss up stream too.

To get around that, you have to measure the pressure at the same time flow is going down the hose:

 

[JoyfulNoise]

Hose.
5 gallon bucket.
Stopwatch.

Let the hose run for one minute outside the bucket then divide 5 gallons by the time it take to fill the bucket. Check water meter at the start of filling and after fill is complete. Done.

Not sure why this has to be turned into a high school science fair project ??

 

[mas985]

Cause some of us like science projects.

 

[JoyfulNoise]

Cause some of us like science projects.

Yes, I do....but we're talking about filling a hole in the ground with water....that wouldn't even qualify as an appropriate entry at my son's middle school science class

Maybe if the pool has a leaky main drain and it's a particularly hot and dry day out, we can talk about 1st derivatives and differential flow rates, evaporative losses, etc...but static fills? Really?

Wake me when it's time to swim