Read up wise.
The reference work for plumbing: hydraulics, heating, pumps, expansion and drinking-water hygiene — explained so it can be used on site.
Articles
Become a plumberGet started · 5 minThe plumber makes sure that water comes in clean, that heat is distributed, and that wastewater leaves safely again. It is a trade in high demand, with good pay and a low barrier to getting started — and at the same time a trade with responsibility, because you work with drinking water, gas and heat, where safety has to be right. Here is why you should consider the trade.Water velocity in pipes — why it mattersHydraulics · 11 minWhat the flow velocity depends on, how it is calculated from flow rate and diameter, and why too high a velocity causes noise and erosion.Heat output from water flow — P = q · c · ΔTHeating · 10 minThe relationship between flow, temperature difference and transferred heat output in a water-based system, with a worked example.Pipe content — how much water the system holdsHydraulics · 9 minHow the water content of a pipe run is calculated geometrically, and what it is used for, e.g. with the expansion vessel and filling.Pump power — hydraulic power and shaft powerInstallation · 12 minHow a pump's useful power depends on flow and head, how efficiency enters in, and what the operating point means.Expansion in closed heating systemsInstallation · 11 minWhy closed systems must accommodate the expansion of the water, what the expansion vessel and safety valve do, and how the expansion volume is calculated.Drinking-water hygiene and legionellaSafety & rules · 10 minWhy domestic water installations must protect water quality, what promotes legionella, and which principles reduce the risk.DS 439:2024 — the new standard for water systemsSafety & rules · 7 minDS 439:2024 is the first real technical revision of the water standard in nearly 50 years. The simplified dimensioning method is abolished, dimensioning now takes place via the qd method, and there is a tightened requirement for pressure testing of empty pipes before they are hidden. Here are the main points you need to know.DS 432:2020 — drainage, rainwater and high-water-level trapSafety & rules · 8 minDS 432:2020 is the standard for drainage systems. It raised the design rain intensity due to climate change, which points towards larger pipes and requirements for high-water-level traps in low-lying basement installations. Here are the formulas and the indicative figures you work with.Heat pumps — COP, SCOP and the DKK 27,000 subsidy pool.Heating · 8 minThe heat pump is the core of green heat transition. COP measures instantaneous efficiency, SCOP measures efficiency over the entire heating season according to EN 14825. And in 2026 the Heat Pump Pool provides a fixed subsidy of 27,000 kr. per household. Here are the figures and conditions.Floor heating — temperatures, loops and material consumptionHeating · 10 minWater-borne floor heating is low-temperature heating that fits perfectly with heat pumps. DS 469 and EN 1264 set limits for flow and surface temperature, and manufacturers provide rules of thumb for loop length and hose consumption. Here are the figures you dimension according to.Gas installations in 2026 — BEK 1702/2025 and certificate requirementsSafety & rules · 6 minAs of January 1, 2026, a new gas regulation, BEK no. 1702/2025, applies, replacing the old BEK 253/2018. At the same time, the authority has been moved to the Danish Business Authority. Here are the rules on authorization, A/B certificates and what has actually been decided about gas phase-out.Authorisation and KLS — How to Become Professionally ResponsibleGet started · 7 minDrinking water, gas and drainage may only be carried out by authorised companies. The route goes via journeyman certificate, work experience and authorisation training — and every authorised company must have an approved quality management system (KLS). Here are the requirements and the documents you work with on site.Legionella — the temperature requirements you need to knowSafety & rules · 6 minLegionella thrives in lukewarm, stagnant water between 20 and 45 °C. The standard keeps the bacterium down with specific temperature requirements: at least 60 °C in the tank, at least 50 °C at the most distant outlet and in the circulation return. Here are the figures and the real conflict with energy savings.The plumbing profession — from craft to authorized standardThe craft's history · 6 minThe plumbing profession has moved from a craft carried by experience to a documented standard-driven and authorized discipline. Here we stick to the part of the story that can be documented: guild traditions Danish standards for water and sewage authorization requirements for drinking water gas and sewage and today's shift toward low temperature heating and heat pumps.Pipe assembly and materials — brazing, pressing, threading and weldingMaterials · 13 minJoining two pipes so they stay tight for decades is the very foundation of the plumbing trade. Here we cover the four major joining techniques — hard soldering and soft soldering of copper, press fittings, threaded joints for steel pipe and welding — plus material selection against galvanic corrosion and temperature/pressure, and the safety rules that come with hot work.Pressure testing, tightness testing and commissioningExecution · 11 minA pipe is not finished when it's assembled — it's finished when it's been tested for leaks, flushed clean and put into operation with tape on. We cover leakage testing of empty pipes before concealment (the new DS 439:2024 requirement), pressure and leakage testing of water, gas and heating systems, flushing through and the certificates that must be in the file.Mechanical ventilation and indoor climateVentilation · 13 minVentilation technician is one of the plumbing and energy trade's main courses, and healthy indoor climate is a BR18 requirement. Here we cover air exchange and indoor climate requirements (CO2, humidity), balanced ventilation with heat recovery, duct sizing and commissioning, and energy consumption for air transport (SEL) — with the figures you size for in Denmark.District heating — connection, exchanger and coolingHeating · 11 minDistrict heating is the dominant heat source in Danish cities and a central HVAC work area. Here we cover direct and indirect connection, the district heating unit with heat exchanger, why large temperature drop (low return temperature) is incentivised, and the supply/return temperatures you work with — plus the district heating certificate in the education.Refrigeration technology and refrigerant handling (F-gas)Cooling · 13 minWith the heat pump rollout, refrigeration technology has become a core competence in the HVAC trade. We cover the four components of the refrigeration cycle, refrigerants and their global warming potential (GWP), the F-gas Regulation (EU) 2024/573 and the Danish certification and leak detection requirements — work with fluorinated refrigerants is subject to certification.Work environment and safety in plumbing workWork environment · 11 minHVAC work contains some of the construction industry's classic risks: open flame during soldering, asbestos in older installations, heavy lifting, gas and pressurised systems. Here we gather the most important occupational health rules — hot work and fire watch, asbestos regulations, Danish Working Environment Authority's limits for heavy lifting, noise and personal protective equipment.Drain system design — water traps, ventilation and drain stacksSafety & rules · 12 minDS 432 article covers the SIZING — rain and waste water flow, slope and filling degree. Here we look at the system structure itself: the water trap that keeps sewer gas out, the vent that prevents it being siphoned dry, the soil stacks and branch pipes that carry the water away, and the installation of the plumbing fixtures it all hangs from.Solar heating — solar collectors, solar heat tank and frost protectionHeating · 11 minSolar heating is one of the renewable energy competency goals in the HVAC energy education. We cover flat-plate and evacuated tube collectors, the solar heating circuit with freeze protection, stagnation, the solar storage tank and how area and tank are sized to the hot water demand — as well as how solar heating works together with heat pump and district heating.Water treatment — hardness, lime, softening and filtrationInstallation · 11 minWater hardness, lime scaling from hot water use, water softeners, particulate filters and the quality of fill water in closed heating systems (VDI 2035) are everyday plumbing work. Here we gather how water quality affects the installation — and what to do about it.HVAC drawing, symbols and isometryExecution · 11 minDrawing reading and production is an explicit competence goal and the prerequisite for all design. We cover schematic diagrams, pipe routing plan and isometry, DN designation (DS/EN ISO 6708), standardised plumbing symbols (DS/EN ISO 4067) and introductory ICT/BIM and CCS coding.Hot water production — tank, flow-through and sizingHeating · 12 minThe Legionella and district heating articles mention tank and flow-through — here we size the hot water supply itself. We look at the balance between tank size and capacity, simultaneity and peak load for domestic hot water, charge circuit and flow-through water heater, and how Legionella and district heating considerations play a role.