Model # DET-5

Internet #100677607

Store SKU #594885

null 8.5 in. W x 11.5 in. D x 8.5 in. H Pre-Pressurized Steel Water Expansion Tank

8.5 in. W x 11.5 in. D x 8.5 in. H Pre-Pressurized Steel Water Expansion Tank

  • Protects water heater from thermal expansion
  • Thermal expansion may void water heater warranty
  • Required by code in most areas
$39.97 / each
If you buy 3 or more
$35.97 / each
store icon Loading Buying Options...
package icon Loading Buying Options...
Sorry, but we ran into issues loading these options. Please try refreshing.

Frequently Bought Together

Product Overview

You're sure to have hot water when you need it with the Watts Pre-Pressurized Steel Water Expansion Tank. Made from strong, durable steel, this tank can be used with gas, electric or oil heaters. An expansion membrane prevents air and water contact, with a rubber diaphragm that flexes when water heats.

California residents: see   Proposition 65 information

  • Compatible with gas, oil and electric heaters
  • Steel construction with a blue outer finish
  • Tank fitted with expansion membrane to ensure long system life by preventing air and water contact
  • Rubber diaphragm flexes when water heats
  • Maximum 150 psi
  • Maximum temperature is 200 Degree F
  • Note: Product may vary by store

Info & Guides

You will need Adobe® Acrobat® Reader to view PDF documents.  Download a free copy from the Adobe Web site.



Product Depth (in.)
Product Height (in.)
Product Width (in.)


Finish Family
Product Type
Expansion Tank
Product Weight (lb.)

Warranty / Certifications

Manufacturer Warranty
Watts (the "Company") warrants each product to be free from defects in material and workmanship under normal usage for a period of one year from the date of original shipment.

More Products With These Features


Customer Questions & Answers

How do you pressurize the tank? Is there an adapter that is neede to add pressure to the tank?

Asked by: Anonymous
No. It is a standard Schrader type valve. The kind that is on your car or older style bicycles.
Answered by: Chris
Date published: 2016-12-07

can it be mounted inverted?

Asked by: doug
Mounting orientation does not matter. See picture from manufacturer below.
Answered by: hardwired56
Date published: 2017-03-11

Banging in the pipes is caused by?

Asked by: How
An expansion tank should do the trick.
Answered by: kman
Date published: 2017-03-13

I have a 40Gal hot water heater that the pressure relief valve is leaking through the pipe onto the floor

I have a 40Gal hot water heater that the pressure relief valve is leaking through the pipe on to the floor. We just purchased this house and know the heater is only about 5 years old. I assume I should replace the Pressure relief valve and also install a expansion tank, however it was installed with PEX all the way to the heater both cold and hot lines. My question is, what size expansion tank should I get? Can I tap into the PEX and hang the tank some how? I can see this is going to be expensive, not only to buy the tank and valve but also the PEX crimp tool and whatever else I will need to install it.
Asked by: kastengeist
If your pressure relief valve is leaking on to the floor, please replace it as soon as possible. This valve is a safety device to prevent dangerous overpressuring the tank causing it to blow up. If this happens the water heater can spew scalding water on everything and everyone within range with devistating effects and injuries. As far as the crimping tool cost, contact Home Depot in their tool rental department and see if they have this tool available. Other tool rental yards would be another source. The size of the expansion tank should be tied to the size of the water heater. Look up the manufacture of your W/H on the internet and size to their specifications.
Answered by: Snipper
Date published: 2017-02-07
  • y_2017, m_7, d_22, h_21CST
  • bvseo_bulk, prod_bvqa, vn_bulk_1.0.0-hotfix-1
  • cp_1, bvpage1
  • co_hasquestionsanswers, tq_42
  • loc_, sid_100677607, prod, sort_[SortEntry(order=NUM_ANSWERS, direction=DESCENDING), SortEntry(order=SUBMISSION_TIME, direction=DESCENDING), SortEntry(order=LAST_APPROVED_ANSWER_SUBMISSION_TIME, direction=DESCENDING), SortEntry(order=LAST_APPROVED_ANSWER_SUBMISSION_TIME, direction=DESCENDING), SortEntry(order=BEST_ANSWER_FEEDBACK_COUNT, direction=DESCENDING), SortEntry(order=POSITIVE_ANSWER_FEEDBACK_COUNT, direction=DESCENDING), SortEntry(order=NUM_ANSWERS, direction=DESCENDING)]
  • clientName_homedepot
  • bvseo_sdk, java_sdk, bvseo-3.1.1
  • CLOUD, getContent, 74ms

Customer Reviews

8.5 in. W x 11.5 in. D x 8.5 in. H Pre-Pressurized Steel Water Expansion Tank is rated 4.4 out of 5 by 58.
Rated 5 out of 5 by from Here's how you know if this tank will be big enough for you. First, I'm giving this five stars be... Here's how you know if this tank will be big enough for you. First, I'm giving this five stars because the install was super easy and it fixed my problem completely. It's only been about a month, so I can't really talk about the longevity. The problem: water slowly dripping from my pressure relief valve. After a lot of exhausting research, here's what I learned. Everything I could find about the inside pressure of the expansion tank was basically split 50/50. In the end (and it actually says on the box that this comes in) the pressure inside the expansion tank needs to be the same as the pressure of the water coming into the house (with no water running AT ALL in the house while you test it). End of story. My heater no longer leaks, AND this will extend the life of my heater (last one lasted about 4 years) and my water-using appliances. Hope this is helpful!
Date published: 2017-02-08
Rated 5 out of 5 by from Solves relief valve leaks from hot water expansion. After installing our new hot water heater (from Home Depot). I saw that when the tank heated the water, expansion of the water occurred, causing the relief valve to leak water. I installed a water expansion tank and the problem was solved. This also added a surprised second fix. . .. . the water pipes would knock when the toilets would shut off, this reduced that noise, sometimes eliminating it completely. . . cool. Follow the directions, air the tank prior to installation, to what your water pressure is. . . See the photo of our installation. . .as you scroll over the photo you will notice we were restricted on room - but it worked nicely.
Date published: 2013-02-13
Rated 5 out of 5 by from This product is a necessary item for any water heater replacement. The compact size works well wi... This product is a necessary item for any water heater replacement. The compact size works well with limited spaces as today's new regulations requiring larger more insulated water heaters for any new replacement installation.. Be sure and read the directions to set the pressure at the appropriate level.
Date published: 2017-05-23
Rated 5 out of 5 by from Fixed Hot Water Heater Relief Valve Leak My hot water heater's relief valve was leaking, and I replaced it. Unfortunately, the new one exhibited the same problems. A pressure gauge on the hot water heater determined that my home's water system was closed, and the relief valve was just doing its job. I installed this expansion tank on the cold water line going into the hot water heater. It lowered the pressure and resolved my dripping relief valve problem. Please be aware that you will have to pressurize this tank yourself, before you install it, based upon your water system's pressure. I had do 5-6 wraps of Teflon Tape to prevent it from leaking.
Date published: 2014-01-08
Rated 5 out of 5 by from Installation was a breeze. My old expansion tank sprung a leak. After I turned off the circuit breaker and main water and did some quick online homework, I purchased this tank as a replacement. I also purchased a water pressure tester, which you have to use to install the tank. Installation was very easy, requiring a bicycle air pump, tire pressure gauge to check your inflation, teflon tape, and a large wrench. This is handy info for someone who has to do an emergency repair like I did.
Date published: 2012-09-27
Rated 5 out of 5 by from Great Product This product is great. You MUST check the water pressure in your home with a pressure gauge ..(usually 55 psi ).. you can buy a spicket pressure gauge for about 10 bucks. Then you MUST put that much air in your tank if your water pressure is 55 psi then you need 55 lbs of air in the tank. If you fail to do this and hook it up as you buy it at 20 lbs of air in this tank it will fail pre mauture. You also must turn off water to your water heater once a year and open a faucet till it stops and check this tank pressure with tire pressure gauge once a year (write the water psi on the tank so you know how much air has to be in tank). If installed correctly this tank is great :))
Date published: 2012-02-18
Rated 5 out of 5 by from Solved my hot water heater T & P Valve leak problem My Temp & Pressure valve on my hot water heater would leak after using a lot of hot water, such as after a bath or shower. I replaced the valve and it still leaked. After doing some research on the problem, I determined it to be thermal expansion and purchased this product. After installation it solved my problem, no more leak.
Date published: 2012-04-20
Rated 5 out of 5 by from required on a "closed system" After installing a new electric HWT and a pressure reducing valve I required a thermal expansion tank so the heated water volume could go somewhere. I inflated the tank from 20 psi to 76 psi (the same psi as I set the pressure reducing valve) before installing on the cold water line over the HWT using a copper T with a 6" extension of 3/4" copper pipe sweated to a 3/4" female threaded copper adapter. Wrapped the male 3/4" nozzle on the tank with Teflon tape and screwed the tank onto the female adapter and the maximum pressure on the hose bib is 80 psi. No more leaking of the relief valve or my Delta kitchen faucet from the past 160 psi with the HWT on. I have braced the cold water line at the copper T to support the weight of the TE tank which can be mounted vertically up or down and horizontal with adequate support.
Date published: 2014-04-15
  • y_2017, m_7, d_23, h_4
  • bvseo_bulk, prod_bvrr, vn_bulk_1.0.0-hotfix-1
  • cp_1, bvpage1
  • co_hasreviews, tv_0, tr_58
  • loc_, sid_100677607, prod, sort_[SortEntry(order=RELEVANCE, direction=DESCENDING)]
  • clientName_homedepot
  • bvseo_sdk, java_sdk, bvseo-3.1.1
  • CLOUD, getContent, 18ms