{"id":15,"date":"2026-08-31T08:49:11","date_gmt":"2026-08-31T08:49:11","guid":{"rendered":"https:\/\/vas.co.th\/?page_id=15"},"modified":"2026-08-31T10:00:39","modified_gmt":"2026-08-31T10:00:39","slug":"understanding-flow-and-head","status":"publish","type":"page","link":"https:\/\/vas.co.th\/?page_id=15","title":{"rendered":"Understanding Flow and Head"},"content":{"rendered":"\n<div class=\"vas-page vas-knowledge-article\">\n<section class=\"vas-article-hero vas-section\">\n<div class=\"vas-container vas-article-shell\">\n<nav class=\"vas-breadcrumbs\" aria-label=\"Breadcrumb\"><a href=\"https:\/\/vas.co.th\/\">Home<\/a><span>\/<\/span><a href=\"https:\/\/vas.co.th\/?page_id=9\">Knowledge Center<\/a><span>\/<\/span><span aria-current=\"page\">Understanding Flow and Head<\/span><\/nav>\n<p class=\"vas-eyebrow\">Water Pumps<\/p>\n<h1>Understanding Flow and Head<\/h1>\n<p class=\"vas-lead\">Flow describes how much water must move. Head describes the energy the pump must provide to overcome height and resistance.<\/p>\n<\/div>\n<\/section>\n<section class=\"vas-section vas-section--white\">\n<div class=\"vas-container vas-article-shell\">\n<article class=\"vas-article-body\">\n<figure class=\"vas-subject-visual vas-local-technical-figure\"><figcaption>\n<p class=\"vas-eyebrow\">System diagram<\/p>\n<h2>Understanding Flow and Head<\/h2>\n<\/figcaption><div class=\"vas-local-technical-figure__viewport\"><a href=\"https:\/\/vas.co.th\/wp-content\/plugins\/vas-site-prototype-plugin\/assets\/technical\/flow%20and%20head%20(head%20flow%20page).png\" target=\"_blank\" rel=\"noopener\" aria-label=\"Open Understanding Flow and Head at full size\"><img decoding=\"async\" src=\"https:\/\/vas.co.th\/wp-content\/plugins\/vas-site-prototype-plugin\/assets\/technical\/flow%20and%20head%20(head%20flow%20page).png\" alt=\"Diagram explaining pump flow, static head, pressure requirements, friction losses, and common units.\" loading=\"lazy\"><\/a><\/div>\n<p class=\"vas-photo-credit\">Flow and head must be considered together when matching a pump to a system.<\/p>\n<\/figure>\n<section class=\"vas-article-lessons\" aria-labelledby=\"vas-article-lessons-title\">\n<header>\n<p class=\"vas-eyebrow\">Key takeaways<\/p>\n<h2 id=\"vas-article-lessons-title\">What to Know<\/h2>\n<p>Scan the main ideas first. Open \u201cKey points\u201d only when you want the supporting details.<\/p>\n<\/header>\n<p class=\"vas-article-lessons__hint\">Swipe the cards to continue <span aria-hidden=\"true\">\u2192<\/span><\/p>\n<div class=\"vas-article-lessons__grid\" role=\"list\" aria-label=\"Article key takeaways\">\n<article class=\"vas-article-lesson\" role=\"listitem\"><span class=\"vas-article-lesson__number\">01<\/span><\/p>\n<h3>Flow Describes Quantity Over Time<\/h3>\n<p>The left side of the diagram shows water moving through a pipe and a flow meter. Flow tells us how much liquid the pump must deliver during a given period, not how high it can lift the water.<\/p>\n<details>\n<summary>Key points <span>3<\/span><\/summary>\n<ul>\n<li>Common units include litres per second, litres per minute, cubic metres per hour, and gallons per minute<\/li>\n<li>The required value should reflect normal and peak demand<\/li>\n<li>Pipe velocity and storage capacity may limit the practical flow<\/li>\n<\/ul>\n<\/details>\n<\/article>\n<article class=\"vas-article-lesson\" role=\"listitem\"><span class=\"vas-article-lesson__number\">02<\/span><\/p>\n<h3>Static Head Comes From Elevation<\/h3>\n<p>The central illustration measures the vertical difference between the source water level and the destination water level. This elevation difference creates static head that remains even when no water is moving.<\/p>\n<details>\n<summary>Key points <span>3<\/span><\/summary>\n<ul>\n<li>Measure between the relevant source and destination liquid levels<\/li>\n<li>Static head exists even when the system flow is zero<\/li>\n<li>A higher destination or lower source increases the required static lift<\/li>\n<\/ul>\n<\/details>\n<\/article>\n<article class=\"vas-article-lesson\" role=\"listitem\"><span class=\"vas-article-lesson__number\">03<\/span><\/p>\n<h3>Pressure and Friction Add More Head<\/h3>\n<p>If the destination must be pressurized, that pressure must be converted to an equivalent head and added. Friction through straight pipe, elbows, valves, strainers, filters, heat exchangers, and other equipment also adds resistance.<\/p>\n<details>\n<summary>Key points <span>3<\/span><\/summary>\n<ul>\n<li>Friction loss normally rises rapidly as flow increases<\/li>\n<li>Longer or smaller pipework produces more resistance<\/li>\n<li>Dirty filters and partly closed valves can increase the required head<\/li>\n<\/ul>\n<\/details>\n<\/article>\n<article class=\"vas-article-lesson\" role=\"listitem\"><span class=\"vas-article-lesson__number\">04<\/span><\/p>\n<h3>Total Dynamic Head<\/h3>\n<p>The pump must overcome the complete system requirement at the intended flow. In practical terms, total dynamic head combines static elevation, required pressure difference, and friction losses, with the exact calculation depending on the system arrangement.<\/p>\n<details>\n<summary>Key points <span>3<\/span><\/summary>\n<ul>\n<li>Combine elevation, pressure difference, and friction at the design flow<\/li>\n<li>Use the complete piping and equipment arrangement in the calculation<\/li>\n<li>Changing flow changes friction and therefore the total system requirement<\/li>\n<\/ul>\n<\/details>\n<\/article>\n<article class=\"vas-article-lesson\" role=\"listitem\"><span class=\"vas-article-lesson__number\">05<\/span><\/p>\n<h3>Match Flow and Head Together<\/h3>\n<p>A statement such as 50 cubic metres per hour is incomplete without the head at that flow. Likewise, a 30-metre head rating does not reveal how much water the pump will deliver. The selected duty point must specify both values together.<\/p>\n<details>\n<summary>Key points <span>3<\/span><\/summary>\n<ul>\n<li>State the required flow and its corresponding total head as one duty point<\/li>\n<li>Do not select from maximum-flow or maximum-head values independently<\/li>\n<li>Plot the duty against the verified pump curve before confirming a model<\/li>\n<\/ul>\n<\/details>\n<\/article>\n<\/div>\n<\/section>\n<\/article>\n<aside class=\"vas-article-next\">\n<p class=\"vas-eyebrow\">Put it into practice<\/p>\n<h2>Discuss the Right Product for Your Needs<\/h2>\n<p>Use this guide as a starting point. Final selection should be confirmed against the actual system conditions and manufacturer specifications.<\/p>\n<div class=\"vas-actions\"><a class=\"vas-button\" href=\"https:\/\/vas.co.th\/?page_id=22\">Contact Us<\/a><a class=\"vas-button vas-button--secondary\" href=\"https:\/\/vas.co.th\/?page_id=7\">View Water Pumps<\/a><\/div>\n<p><a class=\"vas-text-link\" href=\"https:\/\/vas.co.th\/?page_id=9\">Back to the Knowledge Center <span class=\"vas-icon vas-icon--arrow-right \" aria-hidden=\"true\"><\/span><\/a><\/aside>\n<\/div>\n<\/section><\/div>\n","protected":false},"excerpt":{"rendered":"<p>Home\/Knowledge Center\/Understanding Flow and Head Water Pumps Understanding Flow and Head Flow describes how much water must move. Head describes the energy the pump must provide to overcome height and resistance. System diagram Understanding Flow and Head Flow and head must be considered together when matching a pump to a system. Key takeaways What to&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":9,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_kad_post_transparent":"","_kad_post_title":"hide","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"hide","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"class_list":["post-15","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/pages\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vas.co.th\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15"}],"version-history":[{"count":1,"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/pages\/15\/revisions"}],"predecessor-version":[{"id":39,"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/pages\/15\/revisions\/39"}],"up":[{"embeddable":true,"href":"https:\/\/vas.co.th\/index.php?rest_route=\/wp\/v2\/pages\/9"}],"wp:attachment":[{"href":"https:\/\/vas.co.th\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}