{"id":8678,"date":"2025-02-13T08:56:00","date_gmt":"2025-02-13T07:56:00","guid":{"rendered":"https:\/\/www.idro-elettrica.it\/esperto-risponde\/inlet-manifolds-for-fire-pumps-what-is-prohibited\/"},"modified":"2026-07-01T09:46:57","modified_gmt":"2026-07-01T07:46:57","slug":"inlet-manifolds-for-fire-pumps-what-is-prohibited","status":"publish","type":"esperto-risponde","link":"https:\/\/www.idro-elettrica.it\/en\/esperto-risponde\/inlet-manifolds-for-fire-pumps-what-is-prohibited\/","title":{"rendered":"Inlet Manifolds for Fire Pumps: What Is Prohibited"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><em>Inlet manifolds for fire pumps<\/em>: The answer depends on the hydraulic configuration (above-head or below-head) and the inlet conditions described in the sections cited in the referenced rules.*<\/p>\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li class=\"\"><a href=\"#il-quesito-cosa-si-intende-per-collettori-di-aspirazione\">The question: What is meant by \u201cinlet manifolds\u201d?<\/a><\/li><li class=\"\"><a href=\"#uni-en-12845-soprabattente-e-divieto-di-interconnessione\">UNI EN 12845: Overhead panels and prohibition on interconnection<\/a><\/li><li class=\"\"><a href=\"#soprabattente-la-pompa-jockey-deve-essere-indipendente\">Overpressure: The jockey pump must be independent<\/a><\/li><li class=\"\"><a href=\"#uni-en-12845-sottobattente-e-possibilita-di-interconnessione-con-condizioni\">UNI EN 12845: Underlayment and Interconnection Options (Subject to Certain Conditions)<\/a><\/li><li class=\"\"><a href=\"#condizioni-in-aspirazione-perche-linterconnessione-puo-creare-criticita\">Inlet Conditions: Why Interconnection Can Create Critical Issues<\/a><\/li><li class=\"\"><a href=\"#sottobattente-esempi-di-problemi-con-interconnessione-in-aspirazione\">Sub-section: Examples of Problems with Inlet Interconnection<\/a><\/li><li class=\"\"><a href=\"#cosa-ne-deriva-divieti-e-casi-ammessi-secondo-il-testo\">What this means: prohibitions and permitted cases (according to the text)<\/a><\/li><li class=\"\"><a href=\"#conclusione\">Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n\n<h2 id=\"il-quesito-cosa-si-intende-per-collettori-di-aspirazione\" class=\"wp-block-heading\">The question: What is meant by \u201cinlet manifolds\u201d?<\/h2>\n\n<p class=\"wp-block-paragraph\">When we talk about \u201cinlet manifolds,\u201d we are essentially referring to<strong>the interconnection of the inlet lines<\/strong> of multiple pumps that are connected to the same water supply.<\/p>\n\n<p class=\"wp-block-paragraph\">This issue is not merely a matter of \u201cplant engineering\u201d: the choice affects <strong>the reliability<\/strong> and <strong>continuous operation of<\/strong> the pumps, especially under specific conditions where malfunctions may occur (as noted in the Inlet conditions).<\/p>\n\n<h2 id=\"uni-en-12845-soprabattente-e-divieto-di-interconnessione\" class=\"wp-block-heading\">UNI EN 12845: Overhead panels and prohibition on interconnection<\/h2>\n\n<p class=\"wp-block-paragraph\">In the case of <strong>an overhead installation<\/strong>, the text refers to the section on \u201cinlet piping\u201d and provides a clear instruction:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Where more than one pump is installed, <strong>the inlet lines must not be interconnected<\/strong>.<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">In this configuration, therefore, the installation of <strong>inlet manifolds<\/strong> between main fire pumps is <strong>explicitly prohibited<\/strong>.<\/p>\n\n<h2 id=\"soprabattente-la-pompa-jockey-deve-essere-indipendente\" class=\"wp-block-heading\">Overpressure: The jockey pump must be independent<\/h2>\n\n<p class=\"wp-block-paragraph\">That is not all: it is also specified that, <strong>if a pressure-maintaining (jockey) pump is installed in the upper tank<\/strong>, the <strong>inlet piping<\/strong> and its associated <strong>fittings and valves<\/strong> must be <strong>independent<\/strong> of those of the main pump(s).<\/p>\n\n<p class=\"wp-block-paragraph\">The operational implication is clear: in the upper tank, in addition to the prohibition on manifold connections between the main pumps, <strong>the jockey pump must also have its own dedicated inlet<\/strong>, without sharing it with the main pumps.<\/p>\n\n<h2 id=\"uni-en-12845-sottobattente-e-possibilita-di-interconnessione-con-condizioni\" class=\"wp-block-heading\">UNI EN 12845: Underlayment and Interconnection Options (Subject to Conditions)<\/h2>\n\n<p class=\"wp-block-paragraph\">With regard to the <strong>provision on the lower hinge<\/strong>, the text below introduces an option:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Where more than one pump is provided, the inlet lines <strong>may be interconnected<\/strong> if they are equipped with <strong>shut-off valves<\/strong>;<\/li>\n\n\n\n<li>The purpose is to allow each pump to <strong>continue operating<\/strong> when the other is taken offline for maintenance;<\/li>\n\n\n\n<li>The connections must be <strong>properly sized for the required flow rate<\/strong>.<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">Read at face value, the immediate conclusion would be: in summary, <strong>inlet manifolds for fire pumps<\/strong> can always be built. The text, however, clarifies that <strong>this is not the case<\/strong>. <\/p>\n\n<h2 id=\"condizioni-in-aspirazione-perche-linterconnessione-puo-creare-criticita\" class=\"wp-block-heading\">Inlet Conditions: Why Interconnection Can Create Critical Issues<\/h2>\n\n<p class=\"wp-block-paragraph\">The chapter on <strong>inlet conditions<\/strong> highlights that water supply systems (both above-pipe and below-pipe) serving systems with <strong>deluge valves<\/strong> or <strong>dry hydrant networks<\/strong> require special attention during the overall design process.<\/p>\n\n<p class=\"wp-block-paragraph\">Under certain operating conditions, malfunctions may occur that could result in:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>draining<\/strong> the pump;<\/li>\n\n\n\n<li>pump <strong>cavitation<\/strong>;<\/li>\n\n\n\n<li>phenomena related to exceeding the <strong>inlet capacity<\/strong>.<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">It is also noted that this phenomenon is <strong>particularly pronounced<\/strong> in the case of over-beam installations.<\/p>\n\n<h2 id=\"sottobattente-esempi-di-problemi-con-interconnessione-in-aspirazione\" class=\"wp-block-heading\">Sub-section: Examples of Problems with Inlet Interconnection<\/h2>\n\n<p class=\"wp-block-paragraph\">In the case described below, even if the interconnection were sized for the flow rates involved, the text points out potential problems in typical single-source supply scenarios, for example:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>2 pumps, each operating at 100%<\/strong> capacity: simultaneous operation is not provided for under the regulations; the idle pump may be subject to <strong>air ingress<\/strong> through the interconnection (via devices and potential entry points such as minimum recirculation, diesel heat exchanger cooling, sealing devices, flanges, connections, shut-off valves, etc.);<\/li>\n\n\n\n<li><strong>3 pumps, each<\/strong> operating <strong>at 50%<\/strong> capacity: the system is designed for the simultaneous operation of two pumps; here as well, the idle pump may be subject to <strong>air ingress through<\/strong> the interconnection (with similar dynamics).<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">The key point is the principle stated: \u201csuperior\u201d standalone power supplies, given their high degree of reliability, <strong>must not depend<\/strong> on interconnections that could cause problems stemming from the other interconnected pumps.<\/p>\n\n<h2 id=\"cosa-ne-deriva-divieti-e-casi-ammessi-secondo-il-testo\" class=\"wp-block-heading\">What this means: Prohibitions and Permitted Cases (according to the text)<\/h2>\n\n<p class=\"wp-block-paragraph\">When the passages cited are considered in sequence, the text leads to the following practical conclusions:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>It is expressly prohibited<\/strong> to install inlet manifolds <strong>above the floor slab<\/strong> where two or more pumps (including the jockey pump) are installed.<\/li>\n\n\n\n<li>Inlet manifolds <strong>are prohibited<\/strong> even in cases of <strong>individual water supplies with higher head<\/strong> (for technical reasons related to inlet conditions; this prohibition also applies to jockey pumps).<\/li>\n\n\n\n<li>Inlet collectors <strong>are eligible<\/strong> <strong>only in the case of single, underpressure feed systems<\/strong>, as stated in the final summary of the text.<\/li>\n<\/ul>\n\n<h2 id=\"conclusione\" class=\"wp-block-heading\">Conclusion<\/h2>\n\n<p class=\"wp-block-paragraph\"><strong>Inlet manifolds for fire pumps<\/strong> are not a \u201cstandard\u201d choice: the text in <strong>the footnote<\/strong> explicitly prohibits their use and requires that even the jockey pump be independent. In <strong>the lower section<\/strong>, interconnection may appear possible, but the <strong>inlet conditions<\/strong> and the issue of separate upper feed lines lead to a more restrictive approach, with interconnection permitted only in specific cases. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Inlet manifolds for fire pumps: In the upper section, the prohibition is explicit and also applies to the jockey pump. In the lower section, interconnection \u201cwould seem\u201d possible, but inlet conditions may lead to a prohibition in specific scenarios. <\/p>\n","protected":false},"featured_media":8680,"parent":0,"template":"","meta":{"_acf_changed":false,"_angie_page":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"tags":[552,1087,709,1085,1086,560,720,562,549,570],"class_list":["post-8678","esperto-risponde","type-esperto-risponde","status-publish","has-post-thumbnail","hentry","tag-fire-pumps","tag-inlet-conditions-2","tag-inlet-line","tag-inlet-manifolds","tag-jockey-pump-2","tag-lower-sash","tag-main-fire-pumps","tag-overhead","tag-uni-en-12845","tag-uni-tr-11438"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/8678","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde"}],"about":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/types\/esperto-risponde"}],"version-history":[{"count":0,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/esperto-risponde\/8678\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media\/8680"}],"wp:attachment":[{"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/media?parent=8678"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.idro-elettrica.it\/en\/wp-json\/wp\/v2\/tags?post=8678"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}