--- product_id: 147296513 title: "Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN" price: "€ 10792.75" currency: EUR in_stock: true reviews_count: 9 url: https://www.desertcart.hr/products/147296513-hayward-pool-heater-for-inground-pools-universal-h-series-400 store_origin: HR region: Croatia --- # Low NOx Emissions Cupro Nickel Heat Exchanger 400,000 BTU Power Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN **Price:** € 10792.75 **Availability:** βœ… In Stock ## Summary > 🌊 Dive into Comfort with Hayward's Premium Heating! ## Quick Answers - **What is this?** Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - **How much does it cost?** € 10792.75 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/products/147296513-hayward-pool-heater-for-inground-pools-universal-h-series-400) ## Best For - Customers looking for quality international products ## Why This Product - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **User-Friendly Operation:** Easily manage your heater with front-panel access and an intuitive control pad. - β€’ **Eco-Friendly Performance:** Meet air quality standards with low NOx emissions, making your pool experience greener. - β€’ **Corrosion-Resistant Design:** Enjoy peace of mind with a durable cupro nickel heat exchanger that withstands harsh water conditions. - β€’ **Unmatched Heating Efficiency:** Experience rapid heating with 400,000 BTUs, perfect for any in-ground pool or spa. - β€’ **Energy-Saving Hydraulic Design:** Reduce your energy bills with an innovative design that minimizes pump run time. ## Overview The Hayward W3H400FDN Universal H-Series is a high-performance natural gas heater designed for in-ground pools and spas, featuring a powerful 400,000 BTU output, a corrosion-resistant cupro nickel heat exchanger, and an energy-efficient hydraulic design that reduces operational costs while ensuring eco-friendly performance. ## 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 capabilityβ€”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. Review: Good Unit - Wonder if they Used Soy Wire Insulation as Mice Liked to Eat Them - 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. Review: Best Heater I have Owned - 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 desertcart 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! ## 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 ## Technical Specifications | Specification | Value | |---------------|-------| | Best Sellers Rank | #45,902 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #6 in Swimming Pool Heaters | | Customer Reviews | 4.2 out of 5 stars 181 Reviews | ## Images ![Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - Image 1](https://m.media-amazon.com/images/I/61HANADWcVL.jpg) ![Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - Image 2](https://m.media-amazon.com/images/I/51V-EkKOe0L.jpg) ![Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - Image 3](https://m.media-amazon.com/images/I/61OheYonDVL.jpg) ![Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - Image 4](https://m.media-amazon.com/images/I/71lM3dAa2fL.jpg) ![Hayward Pool Heater for Inground Pools Universal H-Series 400,000 BTU (Natural Gas Pool Heater) Pool and Spa Heater W3H400FDN Replacement for H400FDN - Image 5](https://m.media-amazon.com/images/I/71kU97vnQxL.jpg) ## Available Options This product comes in different **Size** options. ## Customer Reviews ### ⭐⭐⭐⭐⭐ Good Unit - Wonder if they Used Soy Wire Insulation as Mice Liked to Eat Them *by R***B on September 5, 2025* 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. ### ⭐⭐⭐⭐⭐ Best Heater I have Owned *by D***R on September 1, 2023* 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! ### ⭐ Oddly the control panel is not rain proof *by M***N on January 21, 2025* 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. ## Frequently Bought Together - Hayward W3H400FDN Universal H-Series 400,000 BTU Natural Gas Pool and Spa Heater for In-Ground Pools and Spas - Hayward SPX3200UNKIT Union Connector Replacement Kit for Select Hayward Pump and Heater - 2 PACK -CMP Hi-Temp Union 2" inch 2MIP x 2" inch PVC Whisperflo & Intelliflo - 2 PACK --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.hr/products/147296513-hayward-pool-heater-for-inground-pools-universal-h-series-400](https://www.desertcart.hr/products/147296513-hayward-pool-heater-for-inground-pools-universal-h-series-400) --- *Product available on Desertcart Croatia* *Store origin: HR* *Last updated: 2026-05-21*