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Internet #311793698

Model #W3H400FDN

Store SKU #1004869551

Universal H-Series 400,000 BTU Natural Gas Pool Heater

Product Overview

The Universal H-Series Heater is an energy efficient, high performance, installation adaptable commitment to the pool service professional. An industry leading hydraulic design reduces circulation pump run time. The energy efficiency of the Universal H-Series gas heater combines with environmentally friendly low NOx emissions, a standard cupro nickel heat exchanger and ultimate installation flexibility on new or existing equipment pads to responsibly heat a pool or spa today and for years to come. The forced draft system in the Universal H-Series constantly moves air through the combustion chamber at a precise flow rate eliminating outside weather variables that can affect heating performance. Wind conditions are eliminated and there is no install a high-wind stack. Patented bypass design for superior hydraulic performance. 2 in. x 2-1/2 in. CPVC union plumbing connections are perfect for todays larger plumbing systems. Easy to read LED control panel. For indoor/outdoor use note: HAYWARD Universal H-Series heaters meet or exceed the SCAQMD and the SJAPCD low NOx emissions standards in all low NOx areas that apply the SCAQMD standard.
  • Model W3H400FDN
  • Excellent salt water and chemical corrosion resistance
  • Same water velocity through all tubes for faster heating
  • Common union for installation or service, adapts to larger plumbing recommended for greater efficiencies
  • State-of-the-art fin plate heat exchanger with cupro-nickel
  • Professional Installer Recommended
  • Electronic Digital Control
  • 2" PVC Threaded Union
  • 1 Year Manufactures Warranty
  • California Customers Please Note: South Coast Air Quality Management District ( SCAQMD) Area of Jurisdiction REQUIRES a Low Nox Heater be installed. The following 6 California Counties are affected: Los Angeles, San Bernardino, Ventura, Orange, Riverside, & Kern. Installing a non-compliant heater in these counties will void the manufacturer's warranty and could result in a fine from your local code enforcement.
  • Item cannot be refunded/returned without approval and authorization from Home Depot
  • For Indoor Installation a vent top must be purchased separately
  • Easy-to-read L.E.D. digital Control Panel
  • Shop our wide selection of Hayward Pool Heaters

Info & Guides

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


BTU Rating
No Additional Features
Fuel Type
Natural Gas
Heat Exchanger
Ignition Type
Continuous Spark
Outdoor Living Product Type
Pool Heaters
Pool Gallons (approx)
Pool Type
In Ground
Product Weight (lb.)

Warranty / Certifications

Manufacturer Warranty
1 year warranty

Questions & Answers


Installing heater indoors

Asked by Steve January 21, 2021

What is the part number for the indoor vertical venting kit for the new Hayward 400 H series

Does my Hayward Universal H-Series 400,000 BTU Natural Gas Pool Heater allow me to use the pool all winter long in upstate ny?

Asked by Quinn November 15, 2020

How many gallons in your pool? Is there any type of structure over the pool? Do you have an automatic cover? This would be a very expensive endeavor.

what size heater for a 30k gallon pool. want to keep it at 82° . Is 1 1/2" pipe big enough?

Asked by Dean September 20, 2020

What size of gas line do you have and how far is it going to be from the gas valve to your gas meter? What is the surface area of your pool? www.hayward.com check out heater selection guide

i have a 33000 gallon poolhow much btu do i needto heat this pool in 2hrs

Asked by parry September 5, 2020

what temperature are you starting at and how warm do you want to heat it to-

Do you offer installation? if so, price for install at 92545?

Asked by brianA August 9, 2020

no we do not, please go to www.hayward.com and put in your zip code and authorized service stations in your area will come up for your location

My pool is 12 x 20 how much BTU I go to need for a pool with thas dimensions

Asked by Orlando May 4, 2020

need to know more information, your average outside temperature, how fast do you want to heat, what size of supply pipe do you have More information can be found on Hayward's website under sizing your pool heater www.hayward.com

Can I use propane with this heater

Asked by Likepar01 April 27, 2020

no, order a propane heater

Customer Reviews

  • 3.7
    out of 3 reviews
  • 0% recommend this product
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Showing 1-3 of 3 reviews
Can not get heater to run . Contacted Hayward the people they recommend to fix it will not return...
Can not get heater to run . Contacted Hayward the people they recommend to fix it will not return my calls.
by Dan
Excellent Pool Heater.. it heats up entire pool of 20k...
Excellent Pool Heater.. it heats up entire pool of 20k gallons in about 3 to 4 hours...awesome.. highly recommend it..
Rating provided by a verified purchaser...
Rating provided by a verified purchaser
by HomeDepotCustomer
Showing 1-3 of 3 reviews