Hayward W3H400FDN Universal H-Series 400,000 BTU Natural Gas Pool and Spa Heater for Inground Pool Heating
Condition: New
Buy Now, Pay Later
As low as
/ mo
Learn more
- – Up to 36-month term if approved
- – No impact on credit to apply
- – Instant approval decision
- – Secure and straightforward checkout
Ready to go? Add this product to your cart and select a plan during checkout.
Payment plans are offered through our trusted finance partners Klarna, Affirm, Afterpay, Apple Pay, and PayTomorrow. No-credit-needed leasing options through Acima may also be available at checkout.
Learn more about financing & leasing here.
Selected Option
Free shipping on this product
Non-returnable item
Learn more
Non-returnable. Transportation of this item is subject to hazardous materials regulation
View our full returns policy here.
Availability:
In Stock.
Arrives
Apr 26 – Apr 27
Recently Viewed
Size: 400,000 BTU (W3H400FDN)
Features
- EASY TO USE: Intuitive inground pool heater control panel enables easy operation and maintenance. The digital LED display helps maintain pool water temperature while monitoring pool water heater performance with self-diagnostic capabilities
- MULTIPLE COVERAGE OPTIONS FOR POOLS AND SPAS: This gas pool heater and pool and spa heater suits in-ground pools and spas up to 1200 sq ft with a natural gas connection; additional models cover 450, 600, or 750 sq ft
- ENERGY SAVING AND BUILT TO LAST: Efficiently designed pool heater for inground pools helps deliver consistent hot water for swimming pools, reduce pump run time for energy savings, and protect against corrosion caused by unbalanced water chemistry
- SIMPLE INSTALLATION: This 400,000 BTU Hayward natural gas pool heater allows flexible gas and electric connections on the right or left side, with an H-Series built-in 3/4" gas connection for easier fuel line setup
- LOW ENVIRONMENTAL IMPACT: Hayward gas pool heaters for inground use are certified for low-NOx emissions and eco-friendly operation, reducing circulation pump run time while delivering a reliable swimming pool heater solution for inground pools
Description
The Universal H-Series 400,000 BTU Natural Gas Pool & Spa Heater from Hayward provides reliable, long-lasting comfort for pools and spas with a surface area up to 1,200 ft. Built with a durable cupro nickel heat exchanger, it offers exceptional protection against corrosion and premature failure caused by unbalanced water chemistry, ensuring you get season after season of premium heating performance. The Universal H-Series boasts industry-leading hydraulic performance coupled with lightning-fast speed-to-heat capability—so you spend less time waiting, and more time swimming. Its low NOx emissions meet air quality standards in all low-NOx areas, so you can rest easy knowing its environmental impact is low, too.
Product Dimensions: 29.5 x 34 x 24 inches
Item Weight: 195 pounds
Manufacturer: Hayward
Item model number: W3H400FDN
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Apr 26 – Apr 27
This item is non-returnable:
Non-returnable. Transportation of this item is subject to hazardous materials regulation
View our full returns policy here.
Non-returnable. Transportation of this item is subject to hazardous materials regulation
View our full returns policy here.
- Klarna Financing
- Affirm Pay in 4
- Affirm Financing
- Afterpay Financing
- PayTomorrow Financing
- Financing through Apple Pay
Learn more about financing & leasing here.
Similar Products
Top Amazon Reviews
Size: 400,000 BTU (W3H400FDN)
Easy to install. Not cheap, but efficient heater for my large pool. It has been 2yrs, and aside from the mice that ate the wiring harness to the display, it was worked great (display was easy to replace and parts are easily accessible which is also nice to make sure this lasts for a long time to come. I think the wires may have been soy based insulation which may be part of the problem). Otherwise it fit where my prior unit was as I just replaced the 20+ year old unit. Not the quietest of devices, but as this is my first pool/hot tub...not sure if they get quieter.
...
show more
Reviewed in the United States on September 5, 2025 by Rob
Size: 400,000 BTU (W3H400FDN)
So I purchased nearly identical model 17 years ago. Self installed except for need of larger supply line for gas input that required a licensed plumber. While I did have a couple failures related to the odd geckos crawling up behind a circuit board with 220 voltage (part easily obtained from Amazon and replaced myself) and shorting out. The heater performed wonderfully! Fast forward to this spring and it was not working after winter months. No input from control board. Tested things I was sure of to no avail. BUT then realized this was 17 years old! I purchased this newer version and it arrived. Unwired and unplumbed from old and connections identical to new. Rewired and replumbed in about 45 minutes and it was up and running 100%. Highly Recommend Hayward products. I also use there pool pumps and sand filters among other odds and ends. Always satisfied!
...
show more
Reviewed in the United States on September 1, 2023 by Douglas Pilcher
Size: 400,000 BTU (W3H400FDN)
The control panel is not rain proof. During operation a CE error code came on. Unplugging and plugging back in did get it to try and start again but the CE code returned. Waited a few days still the same. After going through enough online reviews it was most likely from a wet circuit board. Sure enough after removing the control panel and the plastic housing that was labeled if removed warranty is voided a wet circuit board was discovered. After several days drying it out like a cell phone I reinstalled it. The heater did then come back to life and heat up but the buttons wouldn't work. The heater was just going into last known operation. So looks like I like many others will need to locate and order a new circuit board. Another issue from other reviews is rodent like getting into it. Not sure how it can be sold as an outdoor designed heater and especially by an established manufacturer.
...
show more
Reviewed in the United States on January 21, 2025 by Mike Richardson
Size: 400,000 BTU (W3H400FDN)
Heater works great had a 200,000 Hayward prior to this and a 20,000 gallon inground pool the 200,000 struggled to keep up and eventually stopped working so I decided to go big with the 400 great move because it pretty much slipped right into the same fittings that the 200 had the only thing I had to change was my gas and that was minimal Had it up and running in a couple hours and heated the pool 20° overnight. The shipping was excellent R & L carriers delivered it. It showed up without a mark on it. It was a few days late, so I was mad about that but other than being a few days late I definitely go back to that company again they did a great job shipping it
...
show more
Reviewed in the United States on August 20, 2023 by jim
Size: 400,000 BTU (W3H400FDN)
So glad I tripped the trigger on this. I went with 'go big, or go home'. I'm only heating a 15,000, but when I want to heat it up for visitors, we live in S. FL we get many, I don't want to have to start days before like I did with a heat pump. And if the weather was cooler, yes it does happen in S. FL, it would take a heat pump forever bypassing the timer and running it 24/7. This brings the pool up three degrees an hour. And with a lightweight cover this can't be beat. And when the visitors want to use the spa it's up to temp in minutes, not hours. If you're just not sure about gas vs. heat pump, take my word for it, this is where you want to be. You don't need to run it as long to get to, and maintain where, you want to be. You could run this thing in the dead of winter no matter where you are. Good luck trying that with a heat pump.
...
show more
Reviewed in the United States on December 10, 2021 by K
Size: 400,000 BTU (W3H400FDN)
I had expected the product ( pool heater) to be the same color as the advertised product but it was not. The heater was easy to handle and install.
Reviewed in the United States on April 30, 2021 by ANDREW
Size: 400,000 BTU (W3H400FDN)
We have now been using the Heater for only 14 months. Two months out of warranty, the redesigned plastic control panel bezel warped, water got in to the control panel electronics and now it has been difficult to get parts to replace. This model has a plastic cover on back that seems to trap/hold the water in place and causes shorts, I have water stains on the electrical circuit board where this happened, when I opened the box there was still water in place on a dry day. Customer service is, pass the problem or non responsive in our experiences. Calls to Hayward are usually a 45 minute approximate hold before someone answers (our first call was dropped by CS).
...
show more
Reviewed in the United States on August 13, 2021 by Bruce C8 Owner
Size: 400,000 BTU (W3H400FDN)
I bought this in Jan 2024. I FINALLY installed it a few weeks ago as one of the last things to do as part of a huge renovation project. Had to run a new gas line etc. it starts right up. No worries. Then I get a HF error. Follow the manual and reset. Nope. Did my research. It’s either a bad board, or a bad gas valve. Their online help is effectively useless, especially if you are on your phone. I’ll call Hayward today. I’ll update this as soon as I get this resolved.
...
show more
Reviewed in the United States on April 25, 2025 by Eric R. Roberts