What Is a Bypass Valve on a Swimming Pool Heater for?

Updated on February 26, 2018
robhampton profile image

Rob is a licensed pool service industry professional with over 20 years of experience.

What Is a Bypass?

The quick answer is that it simply directs the flow of water to prevent it from flowing through the heater. Adjustable valves are used to either bypass the heater or to flow through it allowing the heater to operate.

Heater Bypass Valves
Heater Bypass Valves | Source

Why Is a Bypass Needed?

A pool heater contains copper elements. More specifically, the "heat exchanger." This is the point where the water is actually heated and then returned back to the pool. Although in recent years there has been an increase in production of titanium heat exchangers, most existing pool heaters and heat pumps still have a copper exchanger.

Unbalanced water chemistry, most notably, pH and alkalinity, can create an adverse and unwanted effect on a copper heat exchanger: corrosion. When a heat exchanger becomes corroded, copper will start to release into the pool water causing copper stains.

Severe copper stain
Severe copper stain | Source

When to Bypass the Heater

A pool heater can be costly to operate if used to continuously heat the pool. On average, the heater on a residential pool is used occasionally but doesn't run daily. It's not always necessary to change the bypass valve settings every time the heater is used or each time the pool is finished being heated. It's ok for water to flow through the heater on a continuous cycle unless for the following reasons:

  • Shocking the Pool - If algae forms or the pool turns green, chemicals added to clear the algae will create corrosive properties in the water. Bypass the heater until the pool is clear.
  • Winterizing - Pools in cold climate locations should set the valves to bypass when closing down the pool for the winter.
  • Not Using the Heater - If the heater gets very little or no use, then it should be bypassed. A broken or non-operational heater should NEVER have any water flowing through it.
  • Unbalanced Chemistry - The chemistry in the water should be as close to ideal as possible. No need to bypass the heater when adding a small amount of chemicals for regular or weekly water maintenance.
  • Using Algeacides - Some algae control products are copper based. This is ok to use if you don't have a heater. If an algaecide is used, it should be non-copper based.

Copper Stains in the Pool

Most copper stains are caused from a heater that has a corroded exchanger and is causing copper to enter the water flow. The copper will start to adhere to the floor and walls of the pool finish. When this happens, stains will start to form. This can be a blue or teal colored etched look. The stains can also appear as various sized black spots. In a very severe situation it's possible for the entire surface of the pool to become stained and discolored.

Typically, ascorbic acid is used in conjunction with a metal sequestering agent and other chemical adjustments to remove the stains. Iron stains are usually yellow in color and can be treated similarly.

Positioning the Valves

When running the heater, a bypass valve can be positioned so that not all flow is directed into it. This is known as a partial bypass. The heater can still operate when enough water flows through it. High pressure can occur when trying to force all of the water through the heater. Smaller pool pumps with lower horsepower may require the bypass to allow full flow through the heater and no partial bypass.

Partial Bypass (left and center image)Image on right is full bypass
Partial Bypass (left and center image)Image on right is full bypass | Source

Questions & Answers

  • Can a pool heater be used on a salt system pool?

    Yes. A heater or heat pump, whether it's gas or electric can be used to heat a pool with a salt generator.

© 2018 Rob Hampton


    0 of 8192 characters used
    Post Comment

    • Coffeequeeen profile image

      Louise Powles 

      7 months ago from Norfolk, England

      I wish I had a swimming pool. I love swimming. My mother has one though where she lives in Spain. She's really lucky, she swims every day.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, dengarden.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://dengarden.com/privacy-policy#gdpr

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)