Plate heat exchangers are, of course, devices designed for efficient heat transfer between two liquid circuits. However, they are most commonly used in central heating systems, including DHW - in underfloor heating, cooling systems, and industrial heating applications. Thanks to their compact size and large heat exchange surface area, they are very popular in various fields of heating technology. Today they are perhaps the most popular type of heat exchanger - but is a plate heat exchanger suitable for pools?
Due to their relatively low price and easy availability, plate heat exchangers are sometimes chosen by users for pool water heating. This is usually due to lower purchase costs and often lack of awareness. Unfortunately, this is a solution that may be inappropriate - and can lead to serious damage to the exchanger - meaning it can develop leaks. It also has a fatal impact on pool pumps, but more on that shortly.
It does happen that in some configurations, plate heat exchangers in pools work properly for some time - but this requires giving up pool chemicals and high chlorine concentrations - making it rather impractical, because if not chlorine then what? Changing water once a week? It turns out it's not just about that - but also warranty issues, as the manufacturer may void the warranty simply for using a plate heat exchanger for pool heating, based on using the device beyond its intended purpose. Using it in a pool by default means applying pool chemicals and chlorine concentrations that far exceed the exchanger's specifications.
Standard plate heat exchangers, especially those brazed with copper, are not resistant to contact with pool water containing chlorine and other water treatment chemicals. High-concentration chlorine is not the same as chlorinated tap water. It aggressively attacks copper joints, causing corrosion and ultimately leaks in the plate heat exchanger. As a result, users may face leaks and costly device replacement within a short time.
The most destructive combination is high chlorine concentrations, pool chemicals and salt - which some add to pools to create a bacteria-unfriendly environment or for chlorine generators. Under such conditions, plate heat exchanger leaks can sometimes develop in literally just a few weeks.
Using salt for pool water treatment or as an additive to chlorine generators, water softeners - is a completely separate issue. Salt will always be very destructive to heat exchangers (plate and others), because efficient heat transfer doesn't allow using thicker steel sheets. This leaves relatively thin materials - while salt is extremely corrosive.
Salt is essentially out of the question if we want to use a steel heat exchanger. Whether it's a plate heat exchanger or a pool type. Simply put, salt, even in small amounts, will eventually cause very characteristic pitting corrosion, which is easily recognizable during potential warranty service (very high risk of warranty rejection).
If we decide to use salt in the pool, in any amount - we should use a titanium heat exchanger. Models made of titanium are of course significantly more expensive, but only they can guarantee safe operation in salty or salt-treated environments. Unfortunately, many people approach the salt issue very lightly and believe small amounts can't cause harm. We have to debunk this - even small amounts of salt are enough to cause pitting corrosion, it's just a matter of time. In this case, it's not even about the type of exchanger, but its material.
The same applies when using heat exchangers with groundwater, which also contains salt derivatives and dangerous chlorides.
Using a plate heat exchanger in pool installation can negatively affect not only the device itself but also the operation of pool pumps and their wear rate, significantly increasing the risk of failures over time. This results from the simple fact that plate heat exchangers are designed for standard flow rates, working best with flows typical for central heating or DHW systems. Pool pumps obviously generate at least several times greater flows - heating a pool containing from several to several dozen or hundred thousand liters requires this, which is completely different from heating a system with say 100 or 150 liters of water.
A plate heat exchanger simply isn't adapted to such flows and with excessive flows automatically generates very high pressure drops, which is destructive for pool pumps in the long run. If you choose a pool pump generating 6 or 10,000 liters per hour flow, why would you install a plate heat exchanger that works most efficiently at 2-4,000 liters per hour? Higher flow resistance in an unsuitable plate heat exchanger can overload the pump, shortening its lifespan and increasing failure risk. This is another argument for choosing dedicated pool heat exchangers that ensure not only safety but also longer system durability.
For pool heating, specialized pool heat exchangers should be used, made of materials resistant to aggressive chemicals - most often acid-resistant stainless steel or titanium. These devices are designed specifically for operation in demanding chemical conditions and are fully compatible with pool water.
Their main characteristic in this context is the absence of copper joints - they must have stainless steel connections and brazing. Additionally, they don't have a plate construction - these exchangers consist of tubes because they need to handle large water flows on the pool side - but unlike plate models - without generating excessive hydraulic resistance. They shouldn't unnecessarily burden pumps or lead to their premature wear.
Of course, it should still be remembered that when choosing a steel heat exchanger, salt additives should be avoided, while if we opt for salt - we must use the expensive titanium equivalent.
Using an unsuitable heat exchanger carries not only the risk of its damage. Aggressive chemicals that compromise brazed joints may also penetrate other installation elements - like circulation pumps or piping. In the long term, this may lead to failure of the entire system.
When powering pool heating with a water-glycol mixture (e.g. with solar heating or heat pumps), there's also a risk of harmful glycol entering the pool, requiring not only immediate water replacement but also pool cleaning. Glycol in pipes isn't a problem, but contact with human skin is undesirable.
Although plate heat exchangers may seem attractive due to their price and availability, their use in pool technology is not recommended and is potentially very risky. When choosing the right heat exchanger for a pool, it's worth considering not just cost but primarily the device's purpose and material resistance. Otherwise, instead of savings, we face unnecessary expenses and problems. By choosing such a solution without consulting the seller, you're essentially doing so at your own risk and using the device practically without warranty.
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