Flush, Drain, Refill: The Secret to Hot Tub Hygiene

indoor hot tub on patio, next to tall wooden bench.

Keeping your hot tub clean and sparkling means regular flushing, draining, and refilling to remove impurities and bacteria that have accumulated over time. You’ll usually want to do this every 3-4 months.

If this sounds like a lot of work, read on to discover how easy it is to keep your hot tub in tip-top condition by following our step-by-step guide.

Step 1: Prepare the Necessary Supplies

hot tub spa pool maintenance test, Ph chlorine and bromide levels

Before you begin, gather all the necessary supplies:

  • A hose
  • A submersible pump
  • New hot tub filter (or filters)
  • A spa system flush
  • Wet and dry vacuum (optional)
  • A hose filter
  • A water testing kit

Step 2: Turn off the Power

Technician servicing electrical panel

Hot tubs need a power source to keep the water warm and the jets working. Before working on any hot tub, always turn off the power supply to prevent accidents and ensure your safety.

The safest way to switch off the hot tub is at the GFCI circuit breaker, generally located outside the house. If you can’t find the circuit breaker box, unplug the hot tub at the power outlet. Ensure the hot tub’s display panel is not working before you continue.

If no lights appear on the display panel, the tub is safely powered down, and you can move on to the next step in the process.

Step 3: How To Flush a Hot Tub

Spillway Spas, NS-308, 6-8 Person

Before draining the hot tub, flush the plumbing system to remove any residue and contaminants like grime, slime, and sludge! This is how to flush most hot tubs:

  • Locate and tightly close the drain valve.
  • Add spa system flush to the water – follow the manufacturer’s instructions on the packaging.
  • Turn on the jets and let the system run for about 15 – 30 minutes or one full cycle (as per the manufacturer’s instructions).
  • Once the flushing process is complete, drain the water from the hot tub.

Step 4: How To Drain a Hot Tub

blue, empty hot tub on patio.

Draining a hot tub is easy when you know how. Part of hot tub maintenance is to drain and clean it every 3 – 4 months to ensure clean and sparkling water in your tub. Winterizing is a good idea if you are not using your hot tub for a season.

Hot Tub Drain Valves to Refresh Your Oasis

Hot tub  on patio in need of cleaning

Sitting in a pool of dirty, grimy water is not an option when you are trying to relax! A drain valve, aka drain spigot, is the best and most convenient way to remove dirty, grimy water from your hot tub. 

Hot tubs have a drain valve to allow you to drain old water from the tub and replace it with clean, fresh, sparkling water.

Most hot tub models have 2 water drain valves:

  • The primary drain valve, found at the bottom rim on the outside of the hot tub, allows you to drain the water from the hot tub into a suitable drainage area. Before you drain water from your hot tub, check your local regulations regarding restrictions on discarding chemically treated water.
  • The auxiliary drain valve used for draining the internal hot tub valves.
  • There are two different methods to use when draining a hot tub:

Draining a Hot Tub Using the Built-in Drain

This is the easiest method to drain your hot tub, but it could take a while! Follow these steps:

  • Find the drain valve and turn it wide open. If your hot tub model has 2 valves (a primary and an auxiliary), use the primary to drain most of the hot tub water using the hose. Open the auxiliary to drain the lines.
  • Connect one end of the hose to the primary valve and place the other end of the hose over a suitable drainage area like your lawn. The spigot’s thread is plastic, so take care not to apply too much force when attaching the hose, or it could break.
  • Open the ball valve on the spigot to allow the water to drain out of the tub.
  • Allow the water to drain freely from the hot tub. This could take a few hours.
  • Once the water has drained out of the hot tub, remove the hose.
  • Use a wet and dry vacuum on the jets or run a hose through the jets to ensure there is no dirty water residue left over.

Draining a Hot Tub Using a Submersible Pump

New submersible elektriskpump with a blue plastic housing on a stone floor

If your tub does not have a built-in drain valve, you will need a submersible pump to drain the water. A pump will remove the water much quicker from the hot tub, saving you time. Follow these steps:

  • Place the pump in the deepest end of the hot tub. Follow the manufacturer’s instructions to properly set up and use the pump. If the pump’s outflow hose is too short, attach a hose to extend the length.
  • Pump the water out of the hot tub and into a suitable drainage area.
  • When the tub is empty, switch off the pump, and remove it.
  • Check for any leftover residue and clean out using a wet and dry vacuum or a hose through the jets.

Top tip: Always loosen the unions on the hot tub to allow the water in the lines to drain away. Remove the lowest drain plug to ensure that all the water drains out – check that the water has drained from all the plumbing lines.

Filters for Crystal Clear Hot Tub Water

Hot Tub Technician Performing Scheduled Garden SPA Maintenance. Checking Residue on the Water Filter. Residential Garden Hot Tub Service. Water Quality Maintenance.

Hot tub filters have an important job to do. As the water passes through them, unwanted particles like debris and dirt are trapped in their folds, ensuring clean, uncontaminated water is circulated back into the tub.

Dirty, old, or damaged filters mean dirty, grimy water – yuck!

Always remove the filters from the hot tub after draining the water and check them thoroughly. If they are fairly new, clean them with a filter cleaning solution or rinse them off with warm tap water and re-use them. If the filters are old or damaged, discard them and use new filters in your clean hot tub.

Hot tub filters should be cleaned at least twice a month if your use the hot tub regularly. Modern hot tub filters are designed to last for at least 18 – 24 months, so take care of them, and you will always have crystal-clear hot tub water! (Source) (Source)

Top Tip: This would be the best time to deep clean your hot tub. Find out everything you need to know about keeping your jetted tub clean!

Step 5: How To Refill a Hot Tub

hot tub-feature

Before you begin the refilling process, check the manufacturer’s instructions for any special instructions for your particular hot tub model.

There are different methods to use when refilling your hot tub:

Refill Your Hot Tub Using a Hose

senior man filling hot tub with water after cleaning the hot tob on the screened-in lanai

Placing a garden hose attached to the outside faucet into the hot tub is one of the easiest ways to refill the hot tub, but it could result in an airlock which could damage the hot tub or prevent water from shooting out through the jets into the hot tub.

What is an Air Lock in my Hot Tub?

An airlock results from air getting trapped in the plumbing lines or equipment when refilling the tub. If you turn on the hot tub and water does not come from the jets, you have an airlock!

Refill Your Hot Tub Through the Filter Housing

The best way to refill your hot tub safely is to place the hose into the filter housing. This allows the water to run through the hot tub pipes and prevents air locks.

  • Attach one end of the hose to the outside water faucet.
  • Attach the other end of the hose to the hose filter. This will remove any impurities from the water going into the hot tub.
  • Place the end of the hose filter directly into the hot tub’s filter housing to allow the water to run through the hot tub’s pipes as it fills up.
  • Turn on the water.
  • Your hot tub could take a while to fill up, depending on the size of the hot tub and the water pressure.
  • Switch off the water once it reaches the ideal water level, as stated on the side of the tub and in the manufacturer’s handbook. Ideally, the water should cover the jets and reach to about an inch below the headrests.
  • Remove the hose from the filter housing and replace the filter.
  • Switch the power back on at the circuit breaker to begin heating up the water.

Check The Water Chemicals In Your Hot Tub

Hot tub water needs certain chemicals to keep it clean and sanitized. The correct hot tub chemicals are essential to prevent and kill bacteria and algae, keeping the water sparkling. So, buy the right hot tub chemicals.

Check the water chemical levels using a water testing kit at least once a week to ensure there is no skin and eye irritation from hot tub use. Incorrect water chemistry can allow bacteria into the water and even cause damage to the hot tub!

Watch this great video to see how easy it is to flush, drain and refill your hot tub!

How to Drain and Refill Your HotSpring Spa - Hot Tubs Albuquerque

Why Are There Black Flakes In My Hot Tub?

When we fill our whirlpool tubs and turn them on, the last thing that we expect to see are black flakes spurting out of the jets! 

You have followed the manufacturer’s instructions and cleaned the tub regularly, so what is going on? Why are black flakes jetting out of the jets with the water, and what are they exactly?

Black flakes in your tub could be a result of a few reasons:

  1. The water authorities are adding iron or manganese to the water system. These minerals are not harmful, but the water pumped into your tub could look dirty and possibly stain your plumbing fittings and fixtures.
  2. More likely, bacteria, mold, mildew, or biofilm from oils, soaps, human skin, or other human excrements were left over in the water from the last time the tub was used. Even if you drained the tub, residual warm water remains in the pipes and jets, allowing bacteria to hatch and grow. The next time you use the tub, the bacteria are expelled through the jets in the tub, resembling black or brown flakes.
  3. The water chemistry in your jacuzzi is not balanced. (Here’s a post to help you correctly balance the chemicals in your jacuzzi.)

So How Do I Get Rid of the Flakes?

When you switch on your jacuzzi tub, and black flakes spray out of the jets together with the water, what should you do, and is it safe to enter the tub?


The big problem with jets is that they build up a layer of biofilm which is extremely difficult to get rid of. Biofilm describes a range of microorganisms found in whirlpools and tubs, like leftover soap scum, hair, and other unmentionable things.

Biofilm also includes mold, parasites, dirt, bacteria, and viruses. All of these microorganisms stew in the pipes and plumbing after the water has drained from the tub between uses. 

Clean Out the Jets

The longer the leftover micro-organisms sit in the pipes, the more biofilm or slimy scum grows over them and the harder it is to remove. If you don’t use the jets regularly, the scum inside the pipes dries out and hardens so that when you next use the jets, the flakes peel off the pipes and spray into the tub water.

It would help if you gave the jacuzzi tub a regular soaking clean to prevent any buildup of scum and bacterial growth. 

If your jacuzzi tub or swim spa does have black flakes streaming into the tub the next time you switch on the jets, you’ll want to follow this routine for cleaning the jets.

What’s The Best Temperature For YOUR Hot Tub?

For most people, the best hot tub temperature is 98.6 ºF (37 ºC) because this is the average human body temperature. 

If you find it’s too chilly, slowly increase the temperature until you’re comfortable. 

However, keep in mind that children, the elderly, and pregnant women are more sensitive to higher temperatures than others. 

Young Children

The CDC says children under 5 should not use hot tubs at all due to the risk of drowning. (And older children should be able to stand with their heads above the water.) When older children use the hot tub, limit to 5-10 minutes at 98.6 ºF (37 ºC).


Elderly people shouldn’t soak for longer than 5 – 10 minutes.

Anyone With A Lung Or Heart Condition

People with existing lung and heart conditions should avoid hot tubs altogether because the bacteria that grow in warm water can be harmful. 

Pregnant Women

Pregnant women’s temperatures should not rise above 102.2 ºF (39 ºC). But this can happen very quickly if you spend 5–10 minutes in a hot tub heated to 104 ºF (40 ºC).

Because sitting in warmer water than your body’s temperature will raise your temperature, hot tubs can be harmful to an unborn baby. If you are pregnant, don’t get into a hot bath or hot tub without talking to your doctor first.

Long periods spent in hot water can result in severe heat-related illnesses, so staying in the hot tub for more than 10 minutes at a time is not recommended. Also, keep hydrated. And to maintain track of time, keep a clock visible nearby. 

Hot Tub Hygiene

Good hot tub hygiene comes down to adhering to a routine of flushing, draining and refilling hot tub and then balancing the chemicals and cleaning the jets. Keep a record of your schedule and you’ll enjoy your hot tub more knowing that it’s sparkling clean at all times.

Tags: Draining a hot tub, hot tub filters, Hot tub hygiene, Hot tub hygiene supplies, How to clean a hot tub, How To Refill a Hot Tub

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