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Converting Hot Water Heater To Heat Spa


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I recently purchased a house in Richfield, WI.

It came with an older 7' X 7' Jacuzzi spa on the rear patio.

After replacing both pumps and a number of plumbing components that cracked in a previous winter, the spa is back up and running!

The house has an exposed basement (in the rear) and the spa is located about 15' from the basement doors.

The Spa is currently configured with a single electric heater.

My previous spa (in Florida) also had an electric heater.

The cost to run that spa was about $50 per month, not including chemicals....

I'm assuming a majority of the cost was associated with heating the spa.

I am concerned the spa at the new house will cost about the same and I would like to come up with an efficient solution for heating the spa water.

Since my house in Richfield, WI has gas service I was considering using a standard gas water heater to heat the spa.

From what I have read, an outdoor gas spa/pool heater (with a heat exchange) is not as efficient as en electric spa/pool heater. Is this true???

I can pick up a number of used 40gal~50gal gas water heaters on Craigs-list.

Most of them run anywhere from $50 ~ $100.

Compared to the cost of an outdoor gas heater ($1000 +) an inexpensive "standard" gas water heater seems like a good (and efficient) solution for heating the water in the spa.

I'm assuming I can use a small water circulation pump to move the spa water to and from the heater.

The gas water heater can be installed in the basement given its close proximity to the spa.

My only concern is the chemicals in the spa having a negative effect on the heater tank.

If I am able to replace the anode in the tank on a regular basis, doesn't this solution make sense?

Please let me know what you think.

Positive or negative feedback is appreciated.

Ed

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I recently purchased a house in Richfield, WI.

It came with an older 7' X 7' Jacuzzi spa on the rear patio.

After replacing both pumps and a number of plumbing components that cracked in a previous winter, the spa is back up and running!

The house has an exposed basement (in the rear) and the spa is located about 15' from the basement doors.

The Spa is currently configured with a single electric heater.

My previous spa (in Florida) also had an electric heater.

The cost to run that spa was about $50 per month, not including chemicals....

I'm assuming a majority of the cost was associated with heating the spa.

I am concerned the spa at the new house will cost about the same and I would like to come up with an efficient solution for heating the spa water.

Since my house in Richfield, WI has gas service I was considering using a standard gas water heater to heat the spa.

From what I have read, an outdoor gas spa/pool heater (with a heat exchange) is not as efficient as en electric spa/pool heater. Is this true???

I can pick up a number of used 40gal~50gal gas water heaters on Craigs-list.

Most of them run anywhere from $50 ~ $100.

Compared to the cost of an outdoor gas heater ($1000 +) an inexpensive "standard" gas water heater seems like a good (and efficient) solution for heating the water in the spa.

I'm assuming I can use a small water circulation pump to move the spa water to and from the heater.

The gas water heater can be installed in the basement given its close proximity to the spa.

My only concern is the chemicals in the spa having a negative effect on the heater tank.

If I am able to replace the anode in the tank on a regular basis, doesn't this solution make sense?

Please let me know what you think.

Positive or negative feedback is appreciated.

Ed

Why don't you just insulate the spa better to reduce heat lose? Get a good spa cover with 4 mil wrap and at least 2 lb densitity foam. Merlin Industries and Sunstar both make good covers. Gas pool/heaters is the way to go if you don't want to maintain water temp in the spa. A 100,000 BTU heater can heat a spa pretty quick.

A electric spa/pool heater is the same thing that is in the spa, so why bother.

The hot water heater thing I don't think will work, it won't be fast enough to recover to heat cool water

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I've seen a few systems set up like this and they work well and the owners have been quite happy. Simply put the heater below the water level in the spa and thermostatically pump the spa water through it (turn the heater temp down VERY LOW). Most gas water heaters are 20k to 30k BTU's. Figure a 5.5 kW heater is equal to about 17k BTU's

ONE MAJOR PROBLEM. There's no safety switch, such as a high limit switch, to prevent over heating.

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I've seen a few systems set up like this and they work well and the owners have been quite happy. Simply put the heater below the water level in the spa and thermostatically pump the spa water through it (turn the heater temp down VERY LOW). Most gas water heaters are 20k to 30k BTU's. Figure a 5.5 kW heater is equal to about 17k BTU's

ONE MAJOR PROBLEM. There's no safety switch, such as a high limit switch, to prevent over heating.

One other caution that may or may not apply in this case is any Wisconsin code applicability. In most jurisdictions where electric and gas code is incorporated by regulation into state law, hot tub components (or any components for that matter) must be recognized and/or listed by a recognized testing agency for the intended purpose. We are all familiar with the UL and ETL labels that certify either the tub and/or the individual components for such use. Domestic hot water heaters are not certified for such use, nor could they hope to gain such certification.

I know that any attempt here in Mass to install a gas hot water heater as the heating source for a hot tub could not be done legally. Massachusetts requires that a permit must be pulled for any hot water tank installation, the installer must attest to its legal use and the installation is subject to inspection by the AHJ.

Having said this, it is always possible that such an installation may be legal in WI. I am clueless as to WI stand concerning parts recognition.

John

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I've seen a few systems set up like this and they work well and the owners have been quite happy. Simply put the heater below the water level in the spa and thermostatically pump the spa water through it (turn the heater temp down VERY LOW). Most gas water heaters are 20k to 30k BTU's. Figure a 5.5 kW heater is equal to about 17k BTU's

ONE MAJOR PROBLEM. There's no safety switch, such as a high limit switch, to prevent over heating.

One other caution that may or may not apply in this case is any Wisconsin code applicability. In most jurisdictions where electric and gas code is incorporated by regulation into state law, hot tub components (or any components for that matter) must be recognized and/or listed by a recognized testing agency for the intended purpose. We are all familiar with the UL and ETL labels that certify either the tub and/or the individual components for such use. Domestic hot water heaters are not certified for such use, nor could they hope to gain such certification.

I know that any attempt here in Mass to install a gas hot water heater as the heating source for a hot tub could not be done legally. Massachusetts requires that a permit must be pulled for any hot water tank installation, the installer must attest to its legal use and the installation is subject to inspection by the AHJ.

Having said this, it is always possible that such an installation may be legal in WI. I am clueless as to WI stand concerning parts recognition.

John

If WI is anything like Minnesota......you can do just about anything...but when it goes south....you can blame only one person for it. (yup...look in the mirror)

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