Bucket test accuracy

I've been carefully tracking the water level for about a week and it's down about 0.45 inches per 24 hours. That's almost 1/2" which seems like I might have a slow leak. It's very hot right now, but not unusually windy, around 10mph. Daily high/low is around 95/75. Still, 1/2" seems like a lot.

I've had 3 leaks previously, all in the pipes that lead from the pool area to the equipment pad, which seem to be under a lot of stress. Good news is they are easy to access and fix. I'm not seeing any obvious wet spots in the area where those pipes are, which is how I ultimately confirmed the prior leaks.

I tried the famous bucket test. It's showing loss in the bucket of only 1/4" per 24 hours, compared to 1/2" in the pool. I've done this for several days with very consistent results. I'm starting to wonder if the bucket test is accurate and if there's any way to improve it?

I'm using a 5-gal plastic bucket placed on the top step, filled about halfway up and submerged to about the same level as the pool water. I had to fill it a little higher just so it wouldn't float away.

I started thinking that the surface of the water in the bucket is not exposed to the wind to the same degree as the pool water. Also, the water temperature in the bucket probably cools off faster with the lower air temperature at night as compared to the pool water. Both these factors (I think) would result in less evaporation in the bucket.

Does anyone have any advice on this? Thanks!

I don't know if there's any way to validate the precision of the bucket test, without expensive and elaborate lab equipped processes. If anyone has attempted such a thing, I haven't heard about it. (Of course, I have not read every post here, much less on TFP.)

But . . . it should be very close. There are two things you can do to improve the accuracy of your testing:

1. Cut the bucket off, so the lip of the bucket is only 2 - 3" above the pool water level. (Alternatively, you can arrange the bucket on stacked concrete blocks and pavers, to accomplish the same thing.)

2. Weight the bucket with a bit of stone or brick so you can set the water level in the bucket to the same as it is in the pool.

If you want to compare temperatures between pool water and bucket water . . . or just want an accurate pool temp reading, I can recommend these:

Habor Cooking Thermometer w/ 5.5" Probe

I have 3 - 4 of them that I've accumulated as part of my yogurt making gear, and they are cheap, accurate, and work well. One caution -- they are only water-resistant, not water-proof.
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But . . . after all that, I'm betting you have a actual leak. (Sorry!)

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Thanks for the tips. I have a thermapen instant-read food thermometer. At 8:30am this morning, the pool water was 86 degrees, while the bucket water was 84. The bucket might have been cooler during the night. That's not a big difference, but it could be causing some difference in evaporation rates.

Also, I didn't cut off the bucket, but I set it on a concrete block sitting on the second step and also put a large stone in the bucket. So it's set much deeper into the pool water and the water level in the bucket is much higher... almost same as the pool water level, with only about an inch of bucket sticking out of the water. So this should help equalize both wind exposure and temperature.

I'll let this sit for another 24 hours and see if there's any difference. BTW, I also dug a big hole where we've had leaks before and it's dry as a bone. Of course, if there's a leak, it might be anywhere. But because I know the pipes are under stress in that area, that's the most likely spot.

Sounds reasonable. Let me know what you find.

Well, setting the bucket deeper in the pool water has definitely eliminated any temperature differential. Both are 86 degrees as of 8am this morning.

I'm still losing about 1/4" more water in the pool than in the bucket over 24 hours. But I'm not sure I'm getting a good reading on the levels. The bucket is less stable on the second step and wobbles around a lot. I also had to pull it out for a few hours because our granddaughter came over and wanted to swim. So I'll have to reset everything today and try to get it more stable on the concrete block.

I also need to add some water to the pool... still losing right at 0.44 inches per day after 5 days. My hole in the ground where the pipes are exposed is still dry as a bone. I'll post again after I have a better reading on the bucket levels.

My son was here also. He was a pool tech for 4 years and also owns a pool now. He said that he loses 2.5 to 3 inches per week, which works out to be 0.35 to 0.43 inches per day. From his tech days, he said that evaporation up to 1/2" is not unusual this time of year in Texas. He also said the bucket test is only reliable if you are seeing large differences of at least 3/4" or more.. something about the larger surface area for the pool.

Don't want to get into a family dispute here . . . but if you control water depth, temperature, and exposure to wind (via a low bucket top, relative to the pool) . . . the bucket test is reliable.

Period.

I have close association with some pool techs, and they are ALWAYS in too much of a hurry to do finicky little tasks correctly. Route-based pool service profitability lives or dies by pool call brevity. So, at least for the pool techs I know, it is probably true that "bucket test is only reliable if you are seeing large differences of at least 3/4" or more". But that limitation is not intrinsic to the test itself.