Customer Reviews: Frost King SP57/11C Water Heater Blanket, 3in Thick x 48in Tall x 75in Long, R10
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on January 19, 2009
I got this product through Amazon because my local Home Depots don't sell them here in Austin. The product is just as described, it's basically fiberglass insulation with vinyl on either side. It is NOT sealed together, the way a down blanket is, it's more of a loose sandwich. It's easy to cut with sharp scissors, and you'll need to cut no matter what size water heater you have. Couple of things to note:
- I chose this model because it had the highest R-value (R10) in the description of any blanket/jacket I'd seen. The R-value was mysteriously missing from the product packaging, so now I doubt it was that high. You'd think they would capitalize on being 30% more efficient than the next model..
- I thought, since there is no warning to the contrary, that this was the kind of fiberglass you can handle with your bare hands without getting itchy. It's not, so wear gloves
For the money, I say get one, it can't hurt. Even though my water heater was cool to the touch while on, I can tell it's getting toasty under the blanket.
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on January 11, 2014
I purchased this at Home Depot because I didn't want to wait for it to ship. But with free shipping it would have been the exact same price. Okay, so let me address some "problems" people have raised in their reviews.

1) It does fit just fine. I have a 40 gallon gas hot water heater. Gas hot water heaters have no water in the bottom foot or so of the tank. That's where the burner is. Not only should you not insulate that portion because it won't gain you anything (only insulate where the water is) but you also risk blocking the air intake (very bad idea). A good rule of thumb to find where the bottom of the water is, look for the drain valve. It's installed at the bottom of the water tank. So I installed it with the 48" as the height and the 75" to wrap around. I was left with a good 5-6 inches overlap, so clearly room for a larger tank. Also, you don't want to insulate the top of a gas tank as you risk obstructing air flow into the flue.

2) There is almost enough tape (-half star). I used one long piece to secure the vertical seam (48") and small pieces to secure it at the top. This used all the tape. I'd prefer a few more feet so I could secure it at the bottom (simply to seal in the fiber glass).

3) It's fiberglass, so long pants, long sleeves, gloves, and respirator are a must. When you finish, make sure to shake out your hair, throw clothes in laundry, and take a shower. Don't go walking around your house. I didn't notice a strong smell from it like other fiberglass products.

4) It would be improved by flaps (-half star). Besides one edge, the plastic facing is exactly the same size as the underlying insulation. It would be a lot easier to install, tape, and secure if the plastic was maybe 2 inches larger all around.

5) This is exactly the same price as Thermwell's other insulation blanket which is only 2" thick and R6.7. No clue why anyone would buy that one if they're the same price.

6) This is for indoor use only. Fiberglass looses all insulating value if it gets wet.
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on December 15, 2011
I figured that an item that fits "up to 60gal tank" would fit my meager 40gal. In the end, I did manage to get it to fit, but I had to cut it into multiple pieces. The 75" length was taller than my tank, but the 48" width was not enough to get around the circumference (and no, it would not even remotely fit if rotated 90 degrees). I cut off the excess from the height and taped it to the remainder to enhance the width, and with some stretching, managed to get it around my tank. The small amount of tape provided was enough to hold it all together, but not enough to completely cover the seams as indicated in the installation instructions. Also, the R-value probably suffered a bit from compressing the insulation so that it could fit the tank. They could've won a 5-star vote if they'd included a more reasonable size blanket and a sufficient amount of tape.
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on January 31, 2010
We noticed an immediate difference in the efficiency of our hot water delivery. One water heater is in the garage and the other in the attic, but both deliver a much better, more consistently heated water supply. This is the most cost effective energy saving project we have ever completed.
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on February 8, 2008
Works great on a 50 gallon tank...installed in last then 15 minutes! Not problem and easy to install. I did 2 of them in about 20 minutes. All you need is a pair of scissors.
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on April 6, 2014
This blanket barely wraps around an electric 40 gallon water heater. Yes , I installed it in the correct direction (48" high, 75" around). I had to pull reaaaaal tight to get the blanket to make a complete circumference. The tape included is pretty good but they should include 30 % more tape to acount for securing all the edges, including those cut areas for access to controls, valves, etc. The manufacturer should add another 12" in length and another 24" in height to account for covering the top and the fact that most tanks are 60+ " in height. Either that or start offering blanket kits based on actual height and diameters. One size does not fit all. If you had a 50, 80, or 120 gallon tank, there is no way this product would do the job by itself.
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on January 9, 2011
- as other reviews this is too small for our boiler, but since our boiler is in the corner right at the two walls, I would not able to wrap it around the whole boiler anyways
- be ready for TONS and TONS of fiberglass dust after you are done everywhere in your garage - close car windows, doors to your house... (make sure to wear special clothes, respiratory mask, hat, glasses and gloves) - not exaggerating - you can argue that we are married with fiberglass these days - true - but even after adding blow-in (AttiCat) insulation to the attic it was not so messy job...
- more tape should be provided, used FlexFix from Nashua to fill the missing feets/meeters of tape needed

- after applying the insulated part is about 8F (4C) colder than the uninsulated part - so it really works (reason for 3 stars)

- let you wife know what you are up to so she does not feel surprised seing you hugging the boiler in the garage :) :) :)

Have fun!
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on December 8, 2015
I'm giving this product 2 stars instead of 1 since it was nice and thick. However, it didn't quite fit my 50 gallon electric tank like advertised. The tape supplied wasn't enough to do the job. I wouldn't buy again.
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on April 2, 2015
As other have said, too small. Lets see here circumference is equal to diameter x Pi. So that is 24 inches (diameter of heater) times 3.14 equals 75.4 inches. Yep, a 48" wide heater blanket will NOT fit a 24 inch in diameter tank. Nope, not gonna do it... Do the people who make these things do simple stuff like check the "internet"? Turn it sideways and you will get 95% of it. Need to order 2 of these for a 24" diameter tank. My tank is only 59" tall so they give you extra for the top, but still... If you are not sure something will fit your tank, go on the web, search for circumferance of a circle, and go to and use their handy little calculator. It will tell you what will fit. My old tank was 22" in diameter and if you put this on its side, you will get the top 85% or so insulated, with 2.9 inches to play with. Other than that little detail, it seems like a good, thick blanket. My plumber laughed when I showed him the label, even he knew no way when we took it out of the bag.
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on May 7, 2016
This blanket is worth the price. While it won't cut your energy bill drastically, it will pay for itself in energy costs. I highly recommend making it a 2-person project. I put mine on myself, but, it was not easy, and I had to get a little extra tape to make up for what I wasted trying to get it to stay in place.
I went with 4-stars, because it was cheapest and therefore has a lower insulation rate. If you want more insulation, buy Thermwell's more expensive product. Either way, good products.
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