Seisco Water Heaters

Everything you need on Seisco Water Heaters, including model details, industry rankings and customer reviews, all in one place.

Seisco Water Heater Overview

Seisco International Limited manufactures commercial and residential tankless electric water heaters. The company is headquartered in Houston, Texas. The company is privately held.

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Consumer Reviews of Seisco


  • Very Satisfied
  • Somewhat Satisfied
  • Neutral
  • Somewhat Unsatisfied
  • Very Unsatisfied
  • #21 of 51 Water Heaters
  • 12.5% of customers recommended

Corporate History

In 1986, Microtherm, Inc. introduced the Seisco line of tankless water heaters as the first “whole-house” tankless water heater. In 2007, the company changed its name to Seisco International Limited, apparently renaming itself after its water heaters. (Technically, Seisco International Limited acquired Microtherm and its line of Seisco water heaters.)

Product Lines

Along with their tankless water heaters, Seisco offers the Supercharger, which can be used with both a storage tank or tankless water heater. The supercharger maintains a constant temperature within 1.5 degrees to prevent scalding and will help extend tank water heaters by providing hot water after a storage tank has been exhausted.

Seisco heaters are manufactured in Houston, Texas, with final assembly and packaging in Mexico, qualifying them as a “Buy American” product.


Seisco offers a 10-year limited warranty on all their residential products and a 5-year limited warranty on all commercial products.

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Seisco Water Heater Reviews

Showing 1-5 of 8 reviews

"Seisco Water heater Problems"

4.0 rating
Somewhat Satisfied

I had a whole house (ra-28, I think) installed when I had my house built in 2006. It worked flawlessly until Feb. 2013 when the inlet pipe blew out and flooded the closet where the unit is. We were home, so we were able to shut off the water and power. Contacted Seisco hq in Texas and customer service was excellent. They sent me a new one "pro-rated" at about 1/2 price. A year later, the 2nd one failed the same way. Seisco replaced the unit for free and wanted the busted one back for evaluation. I did some research and found that, when my hot water circulating pump came on, and there were no faucets open, the thermal expansion of the water pushed the plumbing system pressure up to 130+ psi. I added an expansion tank to the circulation loop so that the thermal expansion had a place to go. That solved the over pressure problem. In 2017, after cleaning sediment (from city water supply) out of the chambers by removing the heating elements, it started to leak. Seisco sent me new O-rings, but that didn't help. Closer examination revealed a crack where the heating element screws in (most likely caused by me over-tightening the element). I cannibalized a chamber from my original old unit, but it leaked too (most likely cracked from the original over-pressure condition). Contacted Seisco hq again, and they made me a prorated deal on a new unit at their cost (roughly 1/2 price including shipping. I will be installing a whole house sediment filter so there should be no more reason to open the chambers, and the over- pressure situation has been solved. I expect to now get many years of service from this new unit.

Lauren Millsap

Perris, CA

"Ra-22 four chamber"

1.0 rating
Very Unsatisfied

Do not buy this unit. First one lasted 9 days. Second one lasted 10 days. Both times same failure, heavy electrolysis of brass screw for first level sensor. Experienced flooding and electrical smoking. Breakers did not trip. I sincerely believe that if I was not home to secure water and breakers, my house would have burnt down.



"Don't buy it!"

1.0 rating
Very Unsatisfied

Known issue with leaky chambers for years and years and they still don't fix it. Not only that, they look for loopholes to avoid standing behind their product. They jump at the chance to charge people for replacement parts and units that should be warrantied. They are the definition of bad business. I purchased my unit not quite 3 years ago. It's already trash. Last Monday, after the whole weekend without hot water, I contacted warranty support. Because I couldn't find my original receipt, they wanted to charge me for a new unit, even though they were able to easily confirm the unit was manufactured in 2014 by the serial number. I bit the bullet and made the order, just because I didn't want to have to re-do my electricity and storage room to go with something else. I was promised that I would have the new unit by the next Friday and that I would get confirmation and tracking info by wed. Wed. came and went with no contact and the unit did not arrive on Friday. When I called to see what was going on, they told me "oh yeah, sorry. It's on back order and we can't tell you when we'll have it." NO attempt at all of making situation right. Very little research will show you that this is the norm for Seisco.

Marshall Medlock



1.0 rating
Very Unsatisfied

Purchased the ra-32, supposedly the better model. I have had it for a year and two months and have had nothing but problems from day 1. One month after having it installed ($800 for the unit, plus $3500 to have the power run and installation) it went out spontaneously. I called tech support, she said she would be sending me a new control panel. Never came. I had a lot going on at the time so I just let it be. I was able to get the hot water to come on again when it tripped by flipping the breakers on and off. This happened at least twice a week for almost six months before I decided to call back. They sent me another control panel and then stopped responding to emails when I asked about warranty compensation and what local techs are able to swap out the control panel. Their manager Sarah Thompson is the one who stopped replying to simple questions over email. That was a week and 5 days ago when it was last repaired. Now the unit is out again. I was told to "keep an eye on it", as if that's going to fix it. Oh, and Sarah is conveniently gone on vacation now. So, I asked for Sarah's supervisor at A.O. Smith (the owners of Seisco). They refused to give me his info saying they have to check with Sarah first to see if it's okay. I finally got the guy's name, Augustine Baik. No way to contact other than email. By the way, my wife is 2 weeks overdue pregnant and extremely uncomfortable. I tried making a warm bath for her last night and couldn't do it because the water heater went out again. Do not buy from Seisco! I'm warning you.

Richard S

Dallas, TX

"Better to just throw your money in the trash than to buy a Seisco Tankless Water Heater"

1.0 rating
Very Unsatisfied

Don't waste your money or your time with this company. I have had a Seisco Endless Hot Water Supply Model #28 for 2.5 years. It has needed repairs 4 times. This time, there are no repair parts available. Seisco has left me, and many other customers according to my plumber, without replacement parts to repair their hot water heaters for over a month. Do you really want to buy a product from a company that won't even provide replacement parts to repair their faulty machines? And as if this weren't bad enough, Seisco's customer service has also made weekly false claims about when repair parts will be available, they have sent me false FedEx tracking numbers for repair parts they have "shipped" and stolen my money for repair parts that they did not ship. Like I said at the beginning, don't waste your money or your time with this company.



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