Tubber McGee Posted January 31, 2011 Report Share Posted January 31, 2011 Hello, Just curious as to how much water you lose due to evaporation - getting in/out - splashing! (minimal splashing) Seems like I have been adding about 5 to 10 gallons per month due to the water level going down! When my new tub (HS Vanguard) was delivered in October - I had a fitting that was busted and fixed. Just want to make sure this is about normal and I do not have a small leak. How often do you add water and how much? Thanks Quote Link to comment Share on other sites More sharing options...
spatech (the unreal one) Posted January 31, 2011 Report Share Posted January 31, 2011 Hello, Just curious as to how much water you lose due to evaporation - getting in/out - splashing! (minimal splashing) Seems like I have been adding about 5 to 10 gallons per month due to the water level going down! When my new tub (HS Vanguard) was delivered in October - I had a fitting that was busted and fixed. Just want to make sure this is about normal and I do not have a small leak. How often do you add water and how much? Thanks You left out a key part of the equation; how much are you using the spa and how many people? With regular use thats not a shocking amount. With light use I might worry that you're losing it too quickly. Quote Link to comment Share on other sites More sharing options...
Tubber McGee Posted January 31, 2011 Author Report Share Posted January 31, 2011 Thanks SpaTech! The tub is currently being used about 5 times per week! Usually just me - the whole family (5 of us) once or twice a week! What exacty is causing the water loss? I know this is silly question! Thanks Quote Link to comment Share on other sites More sharing options...
footie Posted January 31, 2011 Report Share Posted January 31, 2011 Thanks SpaTech! The tub is currently being used about 5 times per week! Usually just me - the whole family (5 of us) once or twice a week! What exacty is causing the water loss? I know this is silly question! Thanks I got mine last summer and my water loss was small back then but during the height of winter it got heavier, I'm wondering if this is a case of more evaporation due to greater difference between the air temp and water temp during winter. Any idea? Quote Link to comment Share on other sites More sharing options...
Roger Posted January 31, 2011 Report Share Posted January 31, 2011 Hello, Just curious as to how much water you lose due to evaporation - getting in/out - splashing! (minimal splashing) Seems like I have been adding about 5 to 10 gallons per month due to the water level going down! When my new tub (HS Vanguard) was delivered in October - I had a fitting that was busted and fixed. Just want to make sure this is about normal and I do not have a small leak. How often do you add water and how much? Thanks Take a swim suit out to the tub and dunk it in the water. Then ring it out over a bucket. Do this as many times as you use the tub and see how many gallons you have. Then consider evaporation. Depending on the temp difference between the ambient air temp and your water??? You never mentioned where you live? Is it real steamy? 5-10 gallons could be normal. Seems to me that's about how much I added in the winter (colder months) when I maintained a tub full time. Quote Link to comment Share on other sites More sharing options...
Hillbilly Hot Tub Posted January 31, 2011 Report Share Posted January 31, 2011 In the winter I bring a gallon jug of water out with me because i know this is about what i am going to loss at each use. It saves me from dragging the hose out every few weeks to top off the tub. With swimsuits, i would lose even more water, and bring out 2 gallons at each use. My tub never needs to be topped off doing this, and no...I have no leaks. Quote Link to comment Share on other sites More sharing options...
hd2000 Posted January 31, 2011 Report Share Posted January 31, 2011 I'm probably adding about about 8 gal or so per month in the winter time. In the summer, it's less. I don't know exactly why, but I suspect it has to do with the difference in air temp compared to the heated water temp. I think if the water in the tub was colder, it would evaporate less, but I'm guessing. Throw in relative humidity somewhere in the equation. Quote Link to comment Share on other sites More sharing options...
drylandfarmer Posted January 31, 2011 Report Share Posted January 31, 2011 I am losing around 3 inches water every 2 weeks. Topping it up every 2 weeks. Temperatures outside are very cold creating a lot of steam. Using the tub daily for about 1 hour each time. No leaks that I have found so assuming most of it is evaporating. Quote Link to comment Share on other sites More sharing options...
Jake the dog man Posted January 31, 2011 Report Share Posted January 31, 2011 I add about an inch of water every 6-8 weeks. It gets used 2-4 times a week, year round. Quote Link to comment Share on other sites More sharing options...
chem geek Posted February 1, 2011 Report Share Posted February 1, 2011 For those that are interested, the fairly standard formula for evaporation rates for pools that probably applies to spas as well when they are uncovered is the following: Evaporation (inches/hour) = (4.8824/25.4)*(69.4+30.8*WindInMPH)*(SatVapPress - VapPressInAir)/(1.7988*(597-(597-540)*(WaterTemp/100))) where SatVapPress (inches Hg) = (0.0075006/25.4)*100*6.1121*EXP(((18.678-WaterTemp/234.5)*WaterTemp)/(257.14+WaterTemp)) VapPressInAir (inches Hg) = (0.0075006/25.4)*RelHumidity*6.1121*EXP(((18.678-AirTemp/234.5)*AirTemp)/(257.14+AirTemp)) So you can see that the evaporation rate depends on two primary factors: the amount of wind and the difference between the vapor pressure of air at the water's temperature minus the actual vapor pressure (water content) in air at air temperature. Remember that warmer air holds more water so has a higher saturation vapor pressure. Therefore, unless the air is at 100% relative humidity AND at the same temperature as the water, then evaporation will occur. Evaporation occurs more rapidly when the air is dry (i.e. relative humidity is low) and when the water is warmer. Aeration from the jets acts somewhat like wind. 1 gallon removed from a 350 gallon spa would be equivalent to evaporation of around 0.14 inch. Even if the air was completely dry with no water content at all, evaporation with no wind from a 104ºF spa is only 0.03"/hour. However, with a 5 MPH wind it's 0.09"/hour and a 10 MPH wind it's 0.15"/hour (i.e. one gallon per hour). Quote Link to comment Share on other sites More sharing options...
footie Posted February 1, 2011 Report Share Posted February 1, 2011 I never actually notice the water drop on my tub because of the slave tank under the main tank (Cascade model), the only way for me to see it is remove the pump panel (simple) and view the clear tube that has recommended levels for occupancy. But I generally add more at winter than summer so reckon evaporation is higher during the cooler months. Quote Link to comment Share on other sites More sharing options...
Hotsprung Posted February 1, 2011 Report Share Posted February 1, 2011 I found I was putting quite alot in until I started lifting the cover from both sides and allowing the condensation on the underside to drain back in to the tub, before opening it normally. This has halved the amount I need to top up. Quote Link to comment Share on other sites More sharing options...
mdb007 Posted December 20, 2017 Report Share Posted December 20, 2017 Hello all new member to this forum. we were given a 2003 Sundance marin this summer. I did a fill just above the highest jet in early september. we have used it about a 15 times from 2 to 5 people. Tonight i was checking bromine and ph and notice the water about 2-3 inches low when I looked at the weir gate. fortunately it was warm night so I topped it off with hose. we have kept temp about 97-100 and live in cleveland where the temps are starting to get around 20 at night. when we have it open there is quite a bit of steam coming off and few times it's been fairly windy. I looked all around tub and can't find and moisture so hoping this is normal between evaporation and getting out of tub. any thoughts? Quote Link to comment Share on other sites More sharing options...
wish2fish Posted December 27, 2017 Report Share Posted December 27, 2017 On 1/31/2011 at 1:34 PM, Roger said: Take a swim suit out to the tub and dunk it in the water. Then ring it out over a bucket. Do this as many times as you use the tub and see how many gallons you have. Then consider evaporation. Depending on the temp difference between the ambient air temp and your water??? You never mentioned where you live? Is it real steamy? 5-10 gallons could be normal. Seems to me that's about how much I added in the winter (colder months) when I maintained a tub full time. Swimsuit? Quote Link to comment Share on other sites More sharing options...
Cusser Posted December 28, 2017 Report Share Posted December 28, 2017 I keep my '88 CalSpa at 104 °F 24/7, yes, have a cover. I typically lose under 1 inch of water every few weeks. Quote Link to comment Share on other sites More sharing options...
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