Compare a 24-hour observation
Where did the water level go?
Enter the measured drop in each water level, using the same unit. These are drops from the starting marks, not the remaining depths.
Your comparison will appear here.
Entries stay in this page and are not submitted or saved. This comparison cannot locate a leak, establish water safety, or replace a professional inspection.
Make the numbers useful
Use the tool with confidence.
Take comparable readings first
The EPA WaterSense pool guide describes a bucket comparison over 24 hours. It calls for turning off pool equipment, filling a 2.5–5 gallon bucket about three-quarters full, securing it on a pool step or bench with at least two-thirds submerged, and keeping the bucket water level slightly above the pool level. Mark both starting water levels and compare the drops after the observation. Follow the equipment instructions and get help if you cannot safely arrange the test.
Measure each drop from its own starting mark. A bucket that started at a different depth is not a problem by itself: the comparison uses the change in level, not the two remaining depths. Use the same ruler, units and reading approach for both. Keep notes about weather, covers and any changes during the observation.
Rain, automatic refill, swimming, backwashing or an unstable bucket can make the readings unsuitable for this comparison. Select the interruption box if any of these affected the test. The calculator will withhold the interpretation and volume estimate. It cannot correct those events by subtracting an assumed amount.
What the comparison means
If the pool drops farther than the bucket, extra water loss can suggest a leak. A small gap still needs to be considered alongside the ruler precision and the test conditions. This tool does not decide whether a difference is significant, identify a failed part or tell you to buy a repair product.
Equal measured drops are consistent with evaporation during that observation. They do not rule out an intermittent fault. If the bucket drops farther, check the setup, measurements and possible refilling before treating the result as reassurance. Keep the actual readings instead of recording only a conclusion.
Estimate total volume change for a rectangle
For a rectangular pool, surface length multiplied by surface width gives the surface area. Multiplying that area by the vertical drop gives a volume change. Depth is not an input: this calculation concerns the thin layer represented by the change in water level.
The calculator converts inches to feet by dividing by 12. For millimetres, it first divides by 25.4 to obtain inches. Cubic feet are multiplied by 7.48052 to obtain US gallons. A 15-by-30-foot surface dropping half an inch therefore represents about 140.3 US gallons of total volume change.
This estimate uses the full pool drop. It is not an estimate of leak-only gallons, and it does not subtract bucket evaporation as though that difference were a verified leak rate. Curves, sloping features and irregular pool shapes need an appropriate surface-area calculation; leave the dimensions blank here.
Make the result useful for a repair visit
Keep the observation dates and times, both drops, units, interruptions and any photographs of the starting and finishing marks. Note whether the pattern follows equipment operation or happens consistently, without changing equipment settings solely to diagnose it yourself. A qualified pool professional can use this record alongside an inspection.
For the wider household service file, use the equipment record. Find other browser-based planning tools on the calculators page. This tool sends no readings to HandyTrail and saves none between visits.
Before you decide
Practical questions, answered.
Should I enter water depth or the drop in water level?
Enter the drop from each starting mark over the observation period. Do not enter the remaining depth. Use the same unit for the pool and bucket.
Does a larger pool drop prove there is a leak?
No. A difference may warrant a closer look, but it is not a confirmed diagnosis. Measurement uncertainty, conditions and interruptions can affect the result. Use the linked guide and get appropriate help if there is an equipment or safety concern.
Can I use the volume estimate for any pool shape?
No. The optional volume estimate uses a rectangular surface area. Do not apply that rectangle calculation to a curved or irregular pool.
Does HandyTrail save my entries?
No. The tool does not send your entries to HandyTrail or save them between visits. Keep your own copy of any result you need.