Bucket test accurate?

shiyang100

Well-known member
Jun 11, 2016
153
Boston, MA
I have been studying water evaporation recently, which points me to consider how accurate of bucket test.

One of of the key contributors to pool evaporation is the temp difference between pool water surface and air. Let's assume water temp at night is 80F and the temp is 60F. This will create decent evaporation and the surface temp will go down. However the pool has large supply of warm water, and the surface will keep at 80F. Meanwhile the bucket has limited capacity. So you might end up seeing larger evaporation in pool.

At day time, bucket water gets heated up quicker than pool, so this will increase the evaporation in bucket. You might see more water loss in bucket.

Unless you put bucket immersed into the pool, I started to question how accurate bucket test is. For sure it will give you directional guidance if the leak is significant. But for some small leak saying less than 1/4 in a day, bucket test may provide false positive answer, especially during the night with big temp delta.

am I correct here?
 

CJadamec

TFP Expert
Apr 29, 2016
2,269
Quaker Hill, CT
The bucket in the bucket test is supposed to be submerged in the pool so the opening of the bucket is just at or slightly above water level when you start. If the water in the pool drops significantly more than in the bucket then you probably have a leak. The thermodynamic difference between the pool water and bucket water are insignificant when done that way.
 

shiyang100

Well-known member
Jun 11, 2016
153
Boston, MA
I agree. But if you watch YouTube, few of them submerged the bucket in the pool.

i also want to find out what the margin of error is with bucket test.
 

CJadamec

TFP Expert
Apr 29, 2016
2,269
Quaker Hill, CT
The bucket test isn't really a margin of error kinda of test. But if you were to see a 1/2 inch difference between the pool level and bucket level in 24hrs you probably have a leak.
 

shiyang100

Well-known member
Jun 11, 2016
153
Boston, MA
Agreed. Bucket test will clearly help you if there is a decent size of leak. For many new pool owners, pool leak is one of the worst nightmares owning a pool. I sometimes get paranoid of leak. Even slight difference saying less than 1/8" in bucket test will make me worry. That's why I decided to spend time on science behind it.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
11,446
Bedford, TX
shi,

I had a similar feeling to yours when I did my first bucket test on my pool. I had a hard time measuring with any accuracy and was really unsure if I had a leak or not.

So I made a bucket tester that I had a little more confidence in... I used my tester for a week and found that there was less than an 1/8" of difference between the water level in the bucket and the water level in the pool.

Based on that test, I have to assume that the science behind the bucket test is fairly accurate.



Thanks,

Jim R.
 

needsajet

TFP Expert
LifeTime Supporter
Jan 4, 2016
4,588
Sydney, NSW, Australia
That's a very cool bucket tester, Jim :) Love it!

Relative humidity in the air would have a big effect, but of course would be equal for both bucket and pool. Would the amount of wind affecting the pool, vs. the effect of wind on the water in the bucket make a difference?
 

shiyang100

Well-known member
Jun 11, 2016
153
Boston, MA
I think the big difference is about the water temp in the pool vs in the bucket. Unless the bucket is submerged into the pool, 5-10 degree delta can make a big difference.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,882
Tucson, AZ
One should use the thinnest bucket possible, something like a HomeDepot construction bucket is going to be rather thick and that will insulate the bucket water from achieving good thermal equilibrium with the pool water. A metal bucket would be better but I doubt people would want to put a metal bucket in their pools.

Wind is also a huge factor. If the water in the bucket is far below the lip of the bucket, then any breeze present will have very little impact on the water bucket but have a significant impact on the pool water. Therefore it's always advisable to fill the bucket up and submerge it so that there is not a large barrier to any breeze that might blow.

At the end of the day, the bucket test is a crude measure of pool water leaks. Yo are not going to find a small leak with a bucket test. It works much better for larger leaks where the pool water level changes by a 1/2" or more during a 24 hour period. For most pool sizes, an inch of water represents several hundred gallons (1" in my pool roughly equals 300 gallons of water). Smaller leaks could only be detected by a licensed leak detection professional.
 

pooldv

Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
25,173
FL panhandle
Normal evaporation rate in a pool is 1/8"-1/4" per day. So, it sounds like what you are seeing is normal evaporation that everyone see in their pool. Of course humidity, wind and temp differential from air to water can make that more. But, anything less than 1/4" per day is hard to narrow down. Even if you verified that there was 1/8" more loss in the pool than in the bucket a professional pool leak detection company would likely not be able to find that leak, even if it existed.
 

Other Threads of Interest