How to Drain and Refill Your Hot Tub

Draining and refilling your hot tub is the reset button for water quality. No matter how well you maintain the chemistry, total dissolved solids (TDS) build up over time and the water becomes harder to balance. A fresh fill every 3 months keeps everything running cleanly.

How often should you drain your hot tub?

Every 3 months as a minimum. If you use your tub very frequently, have multiple regular bathers, or notice chemicals stopping working as expected, do it sooner.

A quick rule of thumb: divide the volume of your tub (in litres) by the number of bather sessions per week, then divide by 12. The result is roughly how many weeks between drains.

What you'll need

• Submersible drain pump or gravity drain hose (check if your tub has a built-in drain valve)
• Hot tub cleaner / pipe purge product
• Non-abrasive surface cleaner and sponge
• Clean hosepipe
• Garden or drain to discharge into (check local bylaws — do not drain into a watercourse)
• Fresh chemicals to rebalance

Step-by-step: draining your hot tub

1. Run a pipe purge first — add a hot tub flush product (such as Ahh-Some or Swirl Away) and run the jets for 30 minutes before draining. This loosens biofilm from the pipework and you'll drain it away with the old water.
2. Switch off the tub — always turn off at the isolator before draining. Never run pumps dry.
3. Drain the water — use the built-in drain valve if your tub has one, or use a submersible pump. A 1,500-litre tub takes 1–2 hours to drain fully.
4. Clean the shell — once drained, spray a hot tub shell cleaner and wipe down all surfaces with a soft cloth or sponge. Pay attention to the waterline where oils and scale accumulate. Rinse thoroughly — any cleaner residue will foam when you refill.
5. Clean or replace the filter — this is the ideal time to deep clean or replace the filter cartridge.
6. Rinse the shell — give the tub a final rinse and drain any standing water from the footwell.
7. Refill — use a hosepipe fed through the filter housing (rather than over the edge) to reduce the risk of airlocks. Fill to just above the jets.
8. Power on and test — switch the tub back on and allow it to circulate for 30 minutes before testing and balancing the water.

Balancing fresh water

Fresh tap water in Lincolnshire is moderately hard and slightly alkaline. Start by testing and then adjust in this order:

1. Total Alkalinity — target 80–120 ppm
2. pH — target 7.2–7.6
3. Calcium Hardness — target 150–250 ppm
4. Sanitiser (chlorine or bromine) — target 3–5 ppm

See our water chemistry guide for full details.

Don't want to do it yourself?

A full drain, clean and refill is included in our annual service, or can be booked as a standalone visit. Get in touch to arrange it.