Can you fill tub with hot water

[Gary1911]

Thats my ?? for the day  I am in the northeast and when I get my tub I wanna jump in .  I thought that would shorten my wait. Yes I do know that I cant FILL IT but it may help right?   What do ya think a waste of hot water or just a dumb idea Gary

[J._McD]

NOT RECOMMENDED.  Depending on the temperature of the "hot water" you could potentially damage the shell with a concentration of hot water.

Fill the spa half way and THEN ad hot water if you must, but you are probably wired for 240 volts and that should produce from 8 to 12 degrees per hour.  Tub should be up to temperature within 8 to 10 hours.

[wmccall]

NOT RECOMMENDED.  Depending on the temperature of the "hot water" you could potentially damage the shell with a concentration of hot water.

Fill the spa half way and THEN ad hot water if you must, but you are probably wired for 240 volts and that should produce from 8 to 12 degrees per hour.  Tub should be up to temperature within 8 to 10 hours.

In the NE this time of year, starting temps may still be in the high 40's to lower 50's  I'd say count on 12-16 hours.

[Brewman]

It would do little good, anyway.  Beside the good reasons given for not putting in hot water, how will you keep up the hot water once your tank empties?
 Most people have a 40 or 50 gallon water heater.
Spas are at least a couple hundred gallons, mine holds almost 500.  So 50 gallons of hot water in a 500 gallon spa gets me nothing useful.  
Now if you have one of those instant tankless water heaters, maybe you could keep up.
Brewman

[johnvb]

I would think you would be ok with a tempering (mixing) valve setup, where the outputting water temperature is 104 degrees or lower. Check out the Kohler plumbing website, they sell fixtures used in custom site-built shower setups. I used some of this stuff in our last bathroom renovation, seems to be working great. The cost is $$$ for the larger/higher gpm mixing valves though.

I am thinking about doing this myself. Since we have three 40 gal. gas water heaters for our bathroom jacuzzi tub and hydro/heat pump systems, should be enough capacity as long as the flow doesn't go too high.

[Soakin]

If your hot water runs through a softener, remember that most manufacturers don't want soft water used in their spas, and it may void your warranty.  Patience!

[hotubinn]

You may also damage your water heater.  It should normally be drained on an annual basis, if you haven't been doing this it may very well need replacing afterwards!  You also get a lot of debris from the tank that is then deposited into your tub.

[hottubber]

Gary,
I would fill the spa with regular tap water. No need to use hot water. Turn the power on and put in a couple of ounces of DiChlor shock.  It should heat up at a minimum of 6 degrees per hour. You've waited this long, wait one more day. Let the spa filter out any of the stagnant water that may be in the plumbing lines while tested at the factory. You'll be surprised how nice clean, fresh water feels while soaking.
good luck,

hottubber...

[Chas]

I used to be firmly against filling with hot water, because there are several real bad things you can do to a nice new tub with it. But most have been mentioned above, and if you are careful with it, you will be in your tub much faster.

Let me recap:

Don't use soft water. This lets a lot of people out right away.
Don't put the hot water right into the tub, add some cold first. Best to have two hoses running.
Don't let the temp in the tub get over 104 or you might set off a high-limit device. Shoot for the 90's and let the tub bring it up the rest.
Don't use the drain at the bottom of your water heater, it will blow crud into your tub.
Don't turn the tub on until it's full.
Keep the cover on if you are waiting for the water heater to reheat itself.
It is normal to fill a tub from the filter area, perhaps even through the filter standpipe - but don't do this with hot water, it can trip high-limit devices and possibly damage systems.
If you change the setting of the thermostat on your water heater to get hotter water for tub filling, be SURE you set it back to your normal setting when done, or you may have a scald accident in the shower the next day.

You know what? I think I'll just go back to saying, 'don't do it.'