What amount of hot tub water loss from normal use is considered in an acceptable range?

Davekro

Bronze Supporter
Feb 10, 2024
59
Discovery Bay, CA
Pool Size
335
Surface
Fiberglass
Chlorine
Liquid Chlorine
One thing that seems strange is that my water level on my brand new 2023 Bullfrog A6L (310 gals.) hot tub has been dropping an average of 16.5 gallons per week (2 1/3 gals/ day) in the 23 days since I turned the heater on to heat for use after the water balancing process on 2/8/24. When I noticed the first water level drop on 2/10 I added 14 gallons. The weather and cement pad were dry, so I assumed it was not leaking. I immediately checked to see if the ABS plastic pan was filling up, but saw there are 1/2" holes in the bottom of the pan in the equipment area, so water would escape there. I don't know if it is safe to assume those 1/2" holes in the bottom of the pan would be spaced throughout the pan's bottom surface area, not just in the equipment area, or not. The pan I could see from the front equipment area was completely dry, w/ no signs of water. On 2/15,I added another 20 gallons. Today, 3/2, I added 20 more gallons because I noticed that the water level was down ≈ 5/8"-3/4" from the recommended fill line. Today was the third time I added water, for a total of 54 gallons to date, since I had turned the heater on Feb. 8th, after completing the water balancing process.

On 2/10, when I first noticed that the jets would spray out of the tub for a second when pumps were set to high, I looked and saw that the water level had dropped a half inch or so, so I added water to bring it back to the fill-line (there is a mark in the middle of the filter inlet bezels). Before that, I had to run many 30 min cycles with jets on full to raise the PH, then add acid to drop it again over a two day period. I needed to get my tap water's TA down from 370 ppm, so that took two days with the cover off during those 30 min aeration cycles. I guess evaporation might have been part of my first water drop (but water was +/- 60º F, so not hot).

I have gone in maybe 12-15 times in the 23 days since it started to heat up 2/8. Is this considered within an acceptable range of water loss? Even if there was a water leak and water was leaking into the mostly foam filled area(s) around the tub, it is hard to imagine that the 100% closed-cell foam would absorb any water, let alone 50 gallons without draining some into the ABS pan and out onto the concrete pad. 54 gallons is ≈ 17% of the 310 gallon initial fill to the recommended fill line.

Per the Bullfrog website, they use: Full Foam Insulation. Bullfrog Spas’ 100% closed-cell, full foam design insulates the spa completely to prevent heat escape, even in the coldest climates.

I'd appreciate any insights for this newby.
 
One thing that seems strange is that my water level on my brand new 2023 Bullfrog A6L (310 gals.) hot tub has been dropping an average of 16.5 gallons per week (2 1/3 gals/ day) in the 23 days since I turned the heater on to heat for use after the water balancing process on 2/8/24. When I noticed the first water level drop on 2/10 I added 14 gallons. The weather and cement pad were dry, so I assumed it was not leaking. I immediately checked to see if the ABS plastic pan was filling up, but saw there are 1/2" holes in the bottom of the pan in the equipment area, so water would escape there. I don't know if it is safe to assume those 1/2" holes in the bottom of the pan would be spaced throughout the pan's bottom surface area, not just in the equipment area, or not. The pan I could see from the front equipment area was completely dry, w/ no signs of water. On 2/15,I added another 20 gallons. Today, 3/2, I added 20 more gallons because I noticed that the water level was down ≈ 5/8"-3/4" from the recommended fill line. Today was the third time I added water, for a total of 54 gallons to date, since I had turned the heater on Feb. 8th, after completing the water balancing process.

On 2/10, when I first noticed that the jets would spray out of the tub for a second when pumps were set to high, I looked and saw that the water level had dropped a half inch or so, so I added water to bring it back to the fill-line (there is a mark in the middle of the filter inlet bezels). Before that, I had to run many 30 min cycles with jets on full to raise the PH, then add acid to drop it again over a two day period. I needed to get my tap water's TA down from 370 ppm, so that took two days with the cover off during those 30 min aeration cycles. I guess evaporation might have been part of my first water drop (but water was +/- 60º F, so not hot).

I have gone in maybe 12-15 times in the 23 days since it started to heat up 2/8. Is this considered within an acceptable range of water loss? Even if there was a water leak and water was leaking into the mostly foam filled area(s) around the tub, it is hard to imagine that the 100% closed-cell foam would absorb any water, let alone 50 gallons without draining some into the ABS pan and out onto the concrete pad. 54 gallons is ≈ 17% of the 310 gallon initial fill to the recommended fill line.

Per the Bullfrog website, they use: Full Foam Insulation. Bullfrog Spas’ 100% closed-cell, full foam design insulates the spa completely to prevent heat escape, even in the coldest climates.

I'd appreciate any insights for this newby.
Average evaporation is 1” to 1 1/2 “ per week from my experiences.I take care of our showroom hot tubs which are inside and set at 101 degrees/ covered and they lose 1” a week on average.We carry Hot Spring and Vita which are very high quality as is the brand you have Bullfrog.Maybe the residential hot tub expert can give his opinion when he comes by @RDspaguy
 
The greater the difference between water temp and ambient air temp and the lower the average humidity the more evaporative loss there will be. I've had tubs run overnight in freezing temps with no cover and lose 6" in 8 hours. A good cover helps alot, but doesn't stop it completely, and is of course not helping during use.
There is also carry-out, which is a much bigger factor than you think in a frequently used tub.
Hope that helps.
 
The greater the difference between water temp and ambient air temp and the lower the average humidity the more evaporative loss there will be. I've had tubs run overnight in freezing temps with no cover and lose 6" in 8 hours. A good cover helps alot, but doesn't stop it completely, and is of course not helping during use.
There is also carry-out, which is a much bigger factor than you think in a frequently used tub.
Hope that helps.
Thank you, @RDspaguy and everyone else letting me know this actually IS normal. I have no problem topping it off as needed1-2 times per week as needed. I was just scared that there was a problem with my new tug! Uuuug! What a relief to know this. Thank you for letting me know that the delta in water and ambient air temps air temps is a big factor, and that especially with the cover off the heat loss is extremely high. It was late, and the air temp was +/- 48º F, so about 55ºF lower than the set 103º F set water temp.

Thanks for quantifying water level drops to some examples of water height loss given a few scenarios. So maybe when the cover is off, even with jets not 'manually set to on' (except that one pump would soon kick on low while the heater is trying to keep up with the cups and cups worth of water floating away via steam, maybe that's a similar kw draw (or way more?) than running the clothes dryer on high heat.

I was surprised that my 310 gal tub was struggling to maintain 103º when I was in running one pump at a time, mostly on high speed. I guess that ≈ 55% water to air temp. delta makes it hard for the 4 kw Gecko heater to maintain a set temp. Hmmmn, the equivalent of burning (40) 100 watt incandescent light bulbs will be putting to work the excess solar generation we have had since getting our solar panels installed and PTO being granted 5 months ago. It will be interesting to start to see the energy use vs. solar production as we start having more sunny days. The new 6 kW solar system was planned to cover a hot tub and allowing us to actually start USING our AC, instead of our past pattern of hardly using the AC. ;o) We'll see.
 
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