Heating pool and spa with household tankless hot water heaters

[evanschloss]

Hi,

I've got an unusual situation. I have an inground pool and hot tub in the basement of my home that I inherited. They were previously heated using regular tanked household water heaters, so I know it's possible. Both have good covers and we're recirculating water, so they didn't need to heat the water to any great degree. The water heaters need replacing as they are both around fourteen years old. I'm wondering if the cheap tankless water heaters that are listed on Amazon would work similarly well and if they would save energy costs versus tanked heaters. In discussions about using household water heaters that I have seen before, people are saying that they won't heat enough water fast enough and that pool water heaters are needed. But I know that isn't true for my situation at least. If love to hear any feedback from folks. The hot tub generally needed about three hours to get back up to temperature after prolonged use, about six hours per week. The pool uses a thermostat that activates the water heater and pump off and on as needed.

I don't know what circumstances make tankless heaters more cost effective than tanked versions.

Thanks,
Evan

 

[ajw22]

How many gallons is your pool? Please create your signature with details of your pool. It will help us give more specific advice.

Here is a thread on someone who heated their outdoor pool using a tankless water heater ...

Tankless Water Heater to Heat My Pool

Moved from here. I’m going to hook up tankless water heater to my “smaller” 11000 gallon pool, I’ll update how it goes in a couple months. I'm doing the same thing with my 8,000 gallon pool I'm putting up. I ran my natural gas line outside and bought an $80 3.2 gal/min tankless water heater...

www.troublefreepool.com

Will the water heater be gas?

 

[evanschloss]

Thanks. I'll check it out.
Hopefully my signature shows.
The water heaters have been and will be gas.

 

[mguzzy]

I can't see why it wouldn't work.. the heat output is going to dictate how fast they heat up,.. that's the only think I can thing of you would need to consider. ..

BTW I am intrigued by a pool in your basement.. can you post pics?

 

[ajw22]

I can't see why it wouldn't work.. the heat output is going to dictate how fast they heat up,.. that's the only think I can thing of you would need to consider. ..

The flow rate of a pool pump is much greater then household water flow. The core of a tankless water heater may wear out rapidly from the high water flow.

There are a few issues raised in the thread I linked to above.

 

[mguzzy]

The flow rate of a pool pump is much greater then household water flow. ...

good point.. I didn't think of that.

 

[evanschloss]

The flow rate of a pool pump is much greater then household water flow. The core of a tankless water heater may wear out rapidly from the high water flow.

There are a few issues raised in the thread I linked to above.

I would actually be using a much smaller separate pump for the hot water as opposed to the filter pump. So I imagine that wouldn't be much of an issue. But the continual use for a prolonged time might be. I did read the post you linked to and found it helpful. The only difference is that my pool won't fluctuate with the weather as the air temperature will be consistent. It sounded like it worked well for the other fellow, but I also saw that he had something hooked up to make sure it didn't run for longer than 20 minutes at a time.

 

[evanschloss]

I can't see why it wouldn't work.. the heat output is going to dictate how fast they heat up,.. that's the only think I can thing of you would need to consider. ..

BTW I am intrigued by a pool in your basement.. can you post pics?

Here's an old pic. I took out the giant furnace. So it's much more open now.

 

[mguzzy]

Wow.. that's cool.. Just curious do you really get much use from the solar cover inside? I find mine really is more for preventing radiation to the night sky. Obviously there is no "Solar" in the basement so you must be using it to insulate. Is that really needed in a small room? Or does it help keep the humidity down in that room?

 

[evanschloss]

Wow.. that's cool.. Just curious do you really get much use from the solar cover inside? I find mine really is more for preventing radiation to the night sky. Obviously there is no "Solar" in the basement so you must be using it to insulate. Is that really needed in a small room? Or does it help keep the humidity down in that room?

The cover helps with heat loss and humidity. The basement is a little over 1,000 square feet. When the pool is heated the humidity is dramatic. It had been kept around 90 degrees. Opening the door to the basement sends humid air upstairs, which we want to minimize most of the year. I may also invest in a dehumidifier or venting for the summer.