38°C magnesium soak · Included in every session
Heated Mineral Pool
Most people end their Haven session here. After the intensity of the sauna and the shock of the ice bath, the mineral pool is where the body finally settles, warm enough to stay in for a long time, mineral-rich enough to feel genuinely different from an ordinary pool or hot tub.
Haven’s pool is heated to 38°C and enriched with a blend of magnesium, sodium, and boron, three minerals chosen for what they do to the body during a warm soak, not just for how they make the water feel. It’s included in every 90-minute Haven session alongside the Finnish sauna, steam room, and ice bath.
The blend
Three minerals. Three distinct roles.
The blend isn’t arbitrary. Magnesium, sodium, and boron each interact with the body in different ways during warm water immersion, and together they produce an effect that plain heated water doesn’t replicate.
Magnesium
The primary active mineralMagnesium is involved in over 300 processes in the body, muscle contraction and release, nerve transmission, energy production, and sleep regulation. Most people are chronically low in it, which shows up as muscle tension, poor sleep, anxiety, and fatigue that doesn’t resolve with rest.
At 38°C with open pores, magnesium absorbs transdermally, through the skin, at a meaningful rate. Research has found measurable increases in blood magnesium levels after soaking in magnesium-rich water, particularly when the soak is warm and sustained. It won’t correct a significant deficiency on its own, but for maintenance and recovery it’s a genuinely effective and unusually pleasant delivery method.
Sodium
Water quality and circulationSodium in mineral pools does two things. First, it dramatically changes how the water feels on skin, mineral water has a softness and weightlessness that chlorinated water doesn’t, which is immediately noticeable and makes it more comfortable to stay in longer.
Second, soaking in warm sodium-enriched water supports gentle vasodilation, the widening of blood vessels, which improves circulation without the cardiovascular demand of the sauna. For people with tired legs, poor peripheral circulation, or swollen joints, this is one of the more targeted benefits in the pool.
Boron
Joints and inflammationBoron is less well-known than magnesium but has a solid body of research behind its effects on bone and joint health. It plays a role in how the body metabolises key minerals, calcium, magnesium, and phosphorus, and has demonstrated anti-inflammatory effects in multiple studies.
Its inclusion in the pool is particularly relevant for people dealing with joint stiffness, arthritis, or chronic inflammation. The warm water reduces mechanical load on joints while the boron works on the inflammatory response, a useful combination that goes beyond what heat alone provides.
The pool is part of every session.
BOOK A SESSIONTemperature
The temperature is deliberate
38°C sits just above body temperature, warm enough to be deeply relaxing and to keep pores open for mineral absorption, but below the threshold where the body starts working hard to manage heat.
36.5°C
Core body temperature
Below this and the pool feels cool. Above it, the body relaxes rather than thermally stresses.
38°C
Haven’s mineral pool
Warm enough to stay in for 20–30 minutes comfortably. Pores open. Muscles relaxed. Mineral absorption at its most effective.
40°C+
Most hot tubs
Too hot for extended soaking. The body begins heat-managing rather than recovering. Most people find 40°C+ uncomfortable beyond 10–15 minutes.
The 2°C difference between Haven’s pool and a typical hot tub matters more than it sounds. At 38°C you can stay for as long as you want, which is the point. The mineral absorption and deep relaxation response both require time to develop fully. A temperature that forces you out after 15 minutes works against what the pool is for.
The benefits
The full picture of benefits
Sleep
Magnesium regulates melatonin production and activates GABA receptors, the same pathway targeted by many sleep medications. The core temperature drop after leaving the warm pool also mimics the body’s natural pre-sleep signal. Session nights tend to be noticeably better sleep nights.
Muscle recovery
Muscles need magnesium to fully release after contraction. When levels are low, that release is incomplete, which is what produces persistent tightness that doesn’t respond to stretching. A magnesium soak addresses this at the source rather than mechanically.
Stress and anxiety
Magnesium suppresses the release of stress hormones and moderates the nervous system’s reactivity. Chronically low magnesium amplifies the stress response. Replenishing it doesn’t remove stress, but it reliably lowers the baseline from which you’re responding to it.
Skin
Mineral water is measurably gentler on skin than chlorinated water, no drying effect, no irritation. Magnesium has demonstrated anti-inflammatory effects for skin conditions including eczema and psoriasis. Most people notice their skin feels softer for hours after a soak.
Circulation
Warm water causes blood vessels to dilate and blood flow to increase. At 38°C this happens gently, supporting circulation without the cardiovascular demand of the sauna. Particularly beneficial for people with poor peripheral circulation, cold hands and feet, or post-exercise congestion in the legs.
Joint health
Warm water reduces the gravitational load on joints while buoyancy supports the body. Boron’s anti-inflammatory effect adds a biochemical layer to the mechanical relief. For anyone dealing with arthritis, joint stiffness, or recurring inflammation, the pool is typically the most immediately comfortable space in the building.
Every pass includes the mineral pool.
SEE PRICINGThe ritual
Where the pool fits in your session
Most people end here
After two or three heat-cold cycles through the sauna or steam room and ice bath, the mineral pool is the natural closing chapter of a session. The body is already in a deeply relaxed state; the warm mineral water holds and extends that without introducing new physiological demand.
20–30 minutes is the ideal window
Mineral absorption and the nervous system response both build over time. Under 15 minutes is too short to get the full benefit. There’s no real upper limit, the temperature is comfortable enough to stay as long as you like within your 90 minutes.
It also works as a gentle warm-up
Some people start in the mineral pool before moving to the sauna, particularly those who are new to heat therapy or find jumping straight into 85°C confronting. The pool at 38°C eases the body into warmth and prepares the muscles for more intense heat.
The pool works better after heat than before it
When the body has been through sauna or steam, pores are open, circulation is elevated, and the skin is primed to absorb. A 20-minute soak in this state is more effective than the same soak in isolation. If your time is limited, prioritise the pool after the circuit rather than at the start.
One session, four facilities
Heated mineral pool at Haven Wellness,
Smeaton Grange
The mineral pool is included in every Haven session alongside the Finnish sauna, eucalyptus and peppermint steam room, and ice bath. One session, all four facilities, 90 minutes. Towels provided.