Implementing a Personal Cold Plunge

Disclaimer:

The purpose of this website is to provide general guidance, ideas, and useful tips. We do not provide professional advice and this website should not be relied upon as such a source. Neither North American Sauna Society nor the author (who is unaffiliated with the organization) promote individual techniques, structures, or solutions. Please always consult a qualified professional expert prior to building or acquiring a sauna or any accessory related to sauna bathing such as a shower, cold plunge, place to rest, etc. Always read and follow any relevant manuals and safety instructions and consult a doctor beforehand to determine if sauna bathing and/or associated activities are appropriate and safe for you.

by:
Derek Davis


It was sometime in the late 70’s - I was on a road trip in southern Oregon with university friends and we decided to take a break at McCredie Hot Springs, not far off the Willamette Highway. Soaking in the springs was great, but the submersion afterward in the icy waters of the adjacent Salt Creek really took my breath away. This was my first experience with temperature-cycling and something I would never forget.

A decade later, I was to rediscover this pleasure in Garmisch-Partenkirchen, Germany. There to provide technical support to my company’s marketing team, I lucked into an après-ski event hosted by our sales office at a recreation center, something to which an engineer such as myself would not normally be invited. A large complex, it naturally had a sauna, but more significantly, a 60°F cold plunge. I must have done six rounds back and forth. At that point, the hook was firmly set, and I knew I would eventually have to have my own personal sauna and cold plunge.

So in the early 90’s, when my wife and I were looking to build a new home, we chose a lot that would accommodate an addition once the builder was finished. This addition was to have not only an attic for storage (sorely absent in Arizona homes) and a workshop, but a sauna, shower, cold plunge, and pool-equipment room.

This article provides an overview of our experience in designing and implementing this cold plunge system, something rarely found in a high-end custom home, let alone a mid-range residence such as ours.

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Primary Considerations

There are several points to carefully consider in designing a cold plunge system. I address the major ones below along with the approach I took for each. This is not to suggest mine is the only or best way – indeed, in some cases, I regret the choices I made. Hopefully the reader can benefit from my experiences.


I use the acronym TIWC for Things I Would Change.


Cold Plunge Design

As our cold plunge was to be in new construction (the addition to our house), we were able to easily integrate it with our little sauna/shower complex. It is an in-ground, concrete cylinder 6 feet deep and 42 inches in diameter, holding approximately 450 gallons of water. The inside is tiled in 1” hexagonal shower tile.


Construction steps included:
- excavating an oversized hole
- pouring a concrete base in the bottom
- allowing this to cureplacing a large sonotube
- placing the plumbing fixtures (drains and inlet)
- pouring the walls of the plunge on the outside of the sonotube
- allowing that to cure
- removing the sonotube (peeling it out)
- eventually pouring the slab of the addition around the plunge

Access

Located just across a hallway from the sauna, the plunge is entered via a stainless steel pool ladder. The plunge is too narrow to jump into, something that would be dangerous in any case. With the water depth at 5’ 6”, it is easy to submerge completely with a slight bend of the knees.

TIWC: deepen the plunge to about seven feet to accommodate taller people.

Drainage

We installed a floor drain a foot or so from edge of the cold plunge to capture runoff when exiting the plunge.


Filtering

Just as for a pool or spa, it is important to filter the water in the cold plunge to keep it clean and free of suspended contaminants.

Our system consists of a 2-speed (1 HP or 1/6 HP) main circulation pump with a leaf trap, followed by a 50 sq ft cartridge filter. Two parallel drains set low in the plunge walls opposite each other feed the pump. A single directable inlet set in the plunge wall about 1’ below the water surface feeds back into the plunge. Note that twin drains may be mandated by your local building code so as to prevent a bather from blocking a drain, creating a suction, and being trapped below the surface. This used to be a problem with hot tubs.

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The cold plunge equipment (like our pool equipment) is all located in an adjacent “equipment room”. Thus, unlike typical pool equipment installations, it is protected from the elements. This room has a sunken floor and floor drain, making maintenance tasks much more pleasant.

We run the circulation pump on low-speed 24/7 (for reasons provided later) and the system has worked very well. Nevertheless, there are several TIWCs:

- If possible, downsize the circulation pump to even less than 1/6 HP, as the current water flow could easily be halved or quartered.
- The leaf trap, while important for outside pools, plays no role in this type of installation. I have never, in 18 years, had to remove anything from the leaf trap.
- The filter could also likely be downsized, though perhaps there is little benefit in doing so.

-
Add a skimmer (or rather, a surface-level drain) to the drain system. I originally assumed that since there would be no leaves, a skimmer would be pointless. But a way to capture floating hair would have been very useful. As it is, I’ve had to cobble together a ladder-mounted skimmer bag that fulfills this function – a functional, but not particularly esthetically-pleasing approach.
- Add an auto-filler to compensate for evaporation. Although the rate of water loss is low due to the low temperature, I do have to add an inch or so every couple of weeks.
- Add a third drain in the floor of the plunge along with appropriate valves so that fully emptying the plunge would be possible. Currently, emptying the plunge for cleaning (though I’ve only had to do this once, after 16 years of operation) requires the use of a sump pump to get that last 12 inches of water. A floor drain would also capture sand/other particles that tend to collect and swim around at the bottom.

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Chiller System

We chose to use a large remote drinking-fountain chiller to cool the cold plunge. The chiller is plumbed in to a diversionary loop downstream from the filter, with its own booster pump.

Although the chiller has its own thermostat, we use a timer to control the times of operation.

Of course, there are downsides to this approach:
- the hysteresis of the water temperature is higher than would normally be in the case when utilizing a thermostat; our plunge cycles between 58°F and 62°F over the course of one day
- adjusting the temperature (or range) requires a trial-and-error approach of tweaking the schedule of the chiller rather than simply adjusting a thermostat


However, the upsides are substantial:

- scheduling the chiller to operate only during the hours when electricity in our area is cheapest
- significantly reducing the number of compressor start-up cycles and, thus, presumably increasing the life of the chiller


Until two years ago, the chiller we used was an air-water type – this is to say, the waste heat is removed by blowing (room) air over the hot-side coil of the chiller. So you get cold water on one side, hot air on the other. While this worked well enough, this system had the disadvantages of:

- substantial noise from the blower fan and
- heating the air in the equipment room, thus placing an extra load on the air conditioning for that part of the house

So when the chiller compressor finally failed after 16 years of 6-9 hours/day operation (a decent product life), we replaced it with a water-to-water model. The difference is that the cooling of the hot-side coil is provided by some water source, also with its own booster pump. In our case, that cooling water is from our backyard pool, for which the support equipment is conveniently located in the same equipment room. So now, the equipment room is significantly quieter (no blower fan) and cooler (waste heat goes into the outdoor pool, rather then into the indoor air).

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Sanitizing

Pool water requires some means of sanitizing to kill bacteria, usually through dissolved chlorine – the same applies to a cold plunge. We chose ozonation for this purpose. The ozone is generated in a small UV lamp and drawn through a tube to be injected into the water flow (downstream of all other equipment in the system) through a venturi. The venturi’s required pressure differential is created by a small booster pump.

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Ozone has a low half-life in water, meaning that it only disinfects for about 20 minutes after injection. For this reason, we operate the filtration and ozone injection system continuously (24/7). Since the ozone lamp is not generally power-cycled, its operational life is much greater than normal. In 18 years of operation, I have replaced the lamp only twice, and one of those times wasn’t even due to natural bulb failure.

We have found ozonation to be extremely effective, without the negatives (smell, cost, hassle) associated with chemical usage. In fact, I don’t even have to adjust the pH of the water – something absolutely required when using chlorine. And in 18 years, I’ve only changed out the water twice.


Safety

One easily-overlooked issue is that of child safety. A cold plunge is really no different than a swimming pool and, at least in our case, is in a location that may often not be lighted. And though the ladder is inherently always within reach because the plunge is so narrow, securing access from small children should be considered. In our case, there are three doors to the sauna/shower/plunge complex. Each door is spring-loaded to be self-closing and has a standard door handle with its spring-loaded latch. In addition, each door has a second spring-loaded latch, operated by thumb-turn knob on the interior side and by a key on the exterior side. Removal of the key prevents anyone, especially loose children, from entering the complex by that door, yet does not prevent those within the complex from exiting (for fire safety).


Note that while our local building inspector was very persnickety about safety barriers for our backyard pool, he had no concerns about access to the cold plunge. Apparently, at least in that inspector’s mind and to those at the building department who inspected the plans, no safety barrier was required by code. On the other hand, it would be unfortunate to be nearly done with construction only to have the inspector say “whoops, what about a safety barrier?”


And while we’re on the subject of safety, I should note that local building codes normally require that all electrical pool equipment be earth-bonded to protect bathers from a possible short circuit. This applies to the chiller, all pump motors, ozone generator, etc. In addition, the ladder into the cold plunge must be earth-bonded.

Optional Features

Here are few items we have implemented beyond what’s strictly necessary for a cold plunge.

Pressure Gauges

Usually, there is a pressure gauge built into the filter to alert the user when the filter is clogging up. For your cold plunge, this will likely never happen. But pressure gauges at other points in the system can be useful, both to verify correct operation and to diagnose problems.

In particular, for an ozonation system with venturi injection, it is very useful to have gauges upstream and downstream of the injector so that one can dial-in the pressure drop across it and obtain the desired ozone injection rate.

Waterfall Shower

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In Germany, facilities with a cold plunge frequently also have something called a Schwallbrause or Waterfall Shower. This special type of shower head delivers a high flow-rate sheet of cold water and is great for rinsing off prior to entering the cold plunge.

Unfortunately, the cold water in Phoenix, actually isn’t, at least not in the summer. A better description would be lukewarm.

To address this, I built a heat exchanger, using cold plunge water to cool a separate storage tank. That water, in turn, feeds the Waterfall Shower.

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This is done with another diversionary loop downstream from the chiller output, but upstream from the ozone injector. A small circulation pump drives the water through a copper coil wrapped around the storage tank.


TWIC: Replace the “lukewarm” cold water feed to the regular shower head with the same chilled water of the Waterfall shower head.
Fill Faucet

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Although we do not have an auto-filler to compensate for evaporation, there is a manual faucet directly above the cold plunge, making topping off extremely easy. Even if an auto-filler is implemented, I recommend a separate faucet for two reasons. First, filling the plunge from empty using just the auto-filler will take forever and, second, it is very convenient for refilling the sauna bucket.


System Monitor


First, a bit of background. The ozone system normally includes “gas check-valves” in the delivery tube from the ozone generator to the venturi injector. The purpose of these is a block reverse water flow that can occur if the injection booster pump fails or loses power. Unfortunately, over time these check-valves tend to fail in the open position so that by the time they are needed, they don’t function and the ozone generator is destroyed. This is not just theoretical – I speak from experience.

A more reliable solution uses an in-line float sensor in the delivery tube, detecting reverse water flow so that the main circulation pump can be shut down before water reaches the ozone generator. This is one function of the System Monitor.

A second function is to automatically shut down the chiller and its booster pumps in the event that either the cold plunge or pool main circulation pumps fail or lose power. This assures that the chiller doesn’t either freeze up (on the cold side) or overheat (on the hot side).

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Wrap up

I hope the reader has found this article of interest. I would be more than happy to hear of your own experiences on this topic and can be reached at
derekdavis@cox.net.

Finally, for reference here is a simplified plumbing schematic of our installation:
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The Sauna and the Full Monty

Is there something missing from your sauna experience? The sauna can capture lots of physical and psychological benefits. But if you were not born or raised in a country where saunas reign, you, like me, may stumble to understand what most second graders from those regions know. As a sauna enthusiast living in upstate New York, I've made an attempt to sort out a few of these basics in this brief overview as I continue with my learning process. Before we begin, let me acknowledge a couple of realities. The sauna is an individual experience, so ultimately, you are the expert on preferences. Also, I realize that full control of all elements can probably only be gained if you have your own sauna; but for discussion, let us focus on the optimum, and you can adjust for actual conditions.

First, let me submit that a prime purpose of the sauna is a psychological experience. Many will describe it as meditation. It is a time to slow down, clear the mind, and relax. In addition to the heat, the sauna accomplishes this through its isolated, peaceful, controlled environment. The interior of the sauna is natural and simple, a visual calm. Movements are limited, and bathers speak softly about positive, neutral topics. The dominant smell (and taste as your tongue also takes on the sensation) should be a sweet, deep, wood type. The experience lasts more than a few fleeting minutes, the hustle-bustle of life is put on hold, you are in another world. The key here is a conscious effort to relax yourself and to help others do the same. The sauna is designed for it. Think monk and monastery!

Now let's look at the heat that actuates the perspiration process that brings on that cleansed and rejuvenated feeling. The term "sauna bath" capturers this effect nicely. It took me some time to realize that it is not just about the heat, it is also about the cooling down period. We've all seen the images of the plunge into icy water after the sauna. You need not be so extreme, but you may consider a cooler place to relax after you have engaged sufficient heating. The outdoors may serve well in some geographic areas, and many sauna designs include a room or some form of lounging area for this cooling down activity. With a few cycles of heating up, then cooling down, an lasting effect similar to a workout session is created. This repetition is important and usually results in a head-to-toe feeling of melted butter!


Jon Harbison

Sauna and Health

One of the constant discussion topics that the North American Sauna Society is contacted about is the question of sauna and health. Is the sauna healthy for you and if so, are there clinical studies to prove this?

There has been extensive medical research done on the physiological and emotional effects of regular sauna bathing; the Europeans have mainly studied the traditional saunas and the Japanese the IR bathing, but we haven’t had wide-ranging North American studies. There are also many varying types of heated spaces out there that are marketed as saunas and even more creative ways to use them. Therefore, an important thing when considering the health benefits is the definition of what sauna bathing actually is. Particularly the American sauna bathing sometimes deviates from the more ethnic sauna bathing experiences, such as the Finnish sauna and the claims why people should do sauna are sometimes truthful, sometimes misleading in their promises of a healthy life style.

We have found three user types; there is the occasional newspaper reader that likes his sauna mild; then there is the gym sauna bather with her water bottle and an eye on the gym clock; finally, there is the sauna bather, who repeats the intervals of staying in the heat and cooling off as his/her body tells her to. One would assume that the potential health benefits would intensify, as the sauna experience gets more wholesome. Staying in a heated room for a predefined time is not possible but in lower temperatures. Dipping in a cold lake or a swimming pool for a couple of minutes to cool off craves higher temperatures inside the sauna room to feel comfortable.

The main point is that regular sauna bathing has proven medical benefits, but the results will vary depending upon the individual and the way in which he/she sauna bathes. You do what feels natural to yourself; with sauna bathing there is no place for the idea that it must be painful for it to achieve the benefits. Sauna truly is “not only good for you, it feels good too!” Most of us at the North American Sauna Society represent the idea that only a rejuvenating feeling of repeated rounds of staying in the heat, going out, getting back in, going for a swim or a shower, drinking something while taking a break, and doing this as many times as you yourself find enjoyable is what the sauna experience should be about. If you don’t get your endorphins flowing and you don’t get that fantastic feeling, then your sauna experience is not fully cooperating with you. Feeling of comfort is all that matters. If you are new to the sauna, start slow and work your way up. It will be very rewarding and being outright healthy can be a secondary though, it just makes you feel so good.

Sauna Design; a Heated Space That Should Be Just Right



A sauna in one’s home can be as simple as portable-plug-in type or can be custom-built on-site. Small traditional saunas and nearly all infrared saunas usually come pre-fabricated and just need assembly and an electric outlet to get them running. However, if you want your sauna customized to fit a specific space, or with an array of custom upgrades, and/or need the sauna to accommodate more bathers, say in a gym, you probably will go with a traditional sauna that is built to order. No matter what type, a sauna should be UL and code compliant. Mistakes due to lack of knowledge of design and build can make the sauna space impractical, prevent users from an enjoyable sauna experience and, in worst case, be outright unhealthy or even dangerous.

On the other hand, with proper planning and design, the sauna will be an amenity to add value and architectural appeal to the home or club and provide wellness enhancing benefit for years to come.

When planning your sauna you should make sure you are dealing with people knowledgeable about sauna. It would be even better if these people also had personal experience regarding sauna bathing. Even though sauna bathing is a growing worldwide trend, there are still many architects and contractors who are not too familiar with it and don’t know the difference between a sauna and any other room. Compromises are made due to lack of understanding and can end up causing an uncomfortable sauna experience due to poorly designed benches, improper materials, improper lighting and ventilation. Even basic design flaws such as doors opening inwards or sauna rooms with too high ceilings can cause safety risks and prevent users from enjoying the rejuvenating heat.

Proper design of commercial sauna rooms is particularly important due to heavy day-long use. Not only does the club owner want the sauna to look stunning, it’s equally important sauna comfort, safety and maintenance issues are properly addressed upfront in the planning of the sauna project. Important design criteria include ventilation, proper plumbing to ensure easy cleaning, handicap accessibility features and properly matching the heater kW rating with the room size per UL standards.


Yet, North American Sauna Society’s mission is not to police sauna builders, but to promote sauna bathing. Even though all these issues should be addressed, our concern is that every sauna or infrared room that is not built up to standards prevents users from getting a genuine sauna bathing experience and thus blurring general public’s understanding of what sauna bathing really is.

When you are purchasing or renovating your sauna, in need of replacing your heater, or about to make other improvements, it is a good time to check that your sauna meets the code and doesn’t have operational issues. Check North American Sauna Society’s dealer list, or contact us directly to find a knowledgeable sauna professional to work with.



Sauna Bathing in North America; Similar or Different than Abroad?


A conservative estimate is that there are over a million saunas in North America. There is often a sauna in hotels, gyms, and private clubs and to an increasing extent, also in private homes. North America is a melting pot of most cultures in the world and American sauna bathing can be seen as a mixture of many ethnic and other influences that have consolidated and made the American way of sauna. Besides this, a great and growing trend in American sauna bathing is health conscientiousness/ wellness, which has increased particularly the popularity of infrared rooms (saunas) during the past 10 years.

Sauna-bathing experience differs whether the sauna is traditional, or infrared. It’s a matter of taste which one finds better, but sometimes it can happen that a devoted sauna bather misses some elements in an American sauna that s(he) is used to, regardless of the type. In both cases you should take breaks, and particularly with a traditional sauna you will be highly rewarded if sauna bathing takes place in a space that allows repeated visits to the hot room, relaxation in between, and an ability to take a shower or go for a swim during and after.

Some people say that the modern sauna originates from Finland. There are no such words in the Finnish vocabulary as “dry sauna” at the same time there is no “wet sauna” either it is just “sauna”. Sprinkling water to the heater is a welcome part of sauna bathing, since by it you control the humidity in the room, i.e., the feeling of heat. The most stubborn misunderstanding is that you can’t throw water on to an electric heater. While there can be heaters that are poorly built, all the heaters sold by members of North American Sauna Society are built to take water, and are meant to be used in this way. Not only is it OK to sprinkle water on the heated rocks, it’s an essential part of the sauna bathing experience.

American sauna bathing is sometimes a “side product” of something else; you sauna for the purpose of exercise, weight loss, beauty, etc., and this can sometimes lead to less than optimal locations for sauna rooms. They can be in the far corners of locker rooms, next to exercising equipment, and so forth. For many people abroad sauna is the main attraction and even after a good long exercise it still has its own distinctive purpose. You enjoy the heat, taking breaks and taking it easy. If you are lucky, you even enjoy beautiful scenery both through the sauna window and while cooling off outside. Also, a traditional sauna has to be warm enough to raise your core body temperature to get your endorphins flowing.

There are an increasing number of magnificent saunas in the United States and to back this trend North American Sauna Society is contemplating the idea of starting to certify American saunas and sauna dealers. There is a sauna that fits everybody’s bathing needs and it is paramount that both sellers and buyers know what the customer really wants and needs. Saunas are more affordable than ever, but they are space-consuming dis-investments if they don’t live up to buyers’ expectations. A sauna bathing experience is something intangible and very difficult to convey to people with less knowledge on the topic. The North American Sauna Society’s mission is to be the trusted third party and make sure that objective, unbiased information and advice is given to the general public in the matters of sauna.