Many pool owners have never drained the water from their pools. They wouldn’t know how to drain water from a swimming pool or why they need to drain the water. When the time comes to drain water they usually hire in a professional pool service but this is not necessary.
There are several ways to drain water from a swimming pool which depends on the type of pool and the setup of the pool plumbing and filtration system. Some systems are easy, you just turn a valve and run the pump to remove water from the pool. Otherwise a submersible pump is mandatory to drain an inground pool and highly recommended for an above ground pool otherwise it’s a slow process.
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How to Drain Water from a Swimming Pool
Many people ask me, why you would ever drain the water from an inground pool. Well there are many reasons including:
Why Drain an In Ground Pool?
Winterize the Pool: Some people prefer to drain their pool for the winter and refill it again in the spring rather than try to winterize it with chemicals and cover the pool water.
Painting the Pool: Painted pool surfaces last between 5 and 15 years before requiring repainting. Some owners decide to paint over plaster to further enhance the look of their pool.
Plaster Repair: Swimming pool plaster is made with fine crushed white marble and fine white cement that is smoothed over the rough concrete shell. The surface can be damaged by unbalanced pool water and does deteriorate over time. The average marble plaster pool can last up to 15 or 20 years before requiring renovation. If your pool surface only has minor cracks and etching you can repair that part of the surface with new plaster.
Please read our article on How to Repair Pool Plaster
Clean the Pool: Sometimes a pool requires more extensive cleaning, such as an acid wash, to the pool surface and this can only be achieved when you empty the pool.
Renovate the Pool: If you have an older pool maybe it’s time to renovate the whole pool. This usually involves removing the old plaster, aggregate or whatever lining and replacing it with the latest pool lining technology. Usually at the same time you would replace the hydrostatic valve, skimmer box and filtration system.
Bad Pool Chemistry: If the water chemistry is so out of balance with excessive dissolved solids, cyanuric acid, high pH or high metals it may be easier to replace the water with fresh water than try to fix the pool with more chemicals.
What is hydrostatic pressure in swimming pools?
There is a hidden danger when some inground pools are emptied of water. The pool can lift up or pop out of the ground as there may be pressure built up underneath the pool. When the weight of the water is removed the pressure underneath exerts an upwards pressure on the bottom of the pool. This is common in fibreglass shell pools when they do not have a hydrostatic valve fitted.
Concrete pools always have a hydrostatic valve built into the lowest point of the pool at the deep end which releases pressure from under the pool. It looks like a drain fitting with a cover at the bottom of the pool. Ground water under the pool can flow through the valve into the pool to equalize the pressure.
When you drain your pool down to the last few inches of water and you cannot remove it with a pump you can open the hydrostatic valve by lifting it up and wedging it open to drain the remaining water to the ground. The valve is on a spring that can open upwards into the pool. It’s designed to release pressure underneath into the pool but we can use it to drain water out of the pool by lifting the valve and holding it open until the excess water has drained away.
Please read out article on Hydrostatic Pool Valves
Does my pool have a hydrostatic valve?
If there is a drain like fitting with a cover over it at the bottom of your pool you have a hydrostatic valve.
If you are unsure whether your pool has a hydrostatic valve and whether it is safe to empty it contact a swimming pool contractor for a professional opinion.
When to Drain an Inground Pool
Inground concrete pools are usually lined with pebble aggregate, white marble plaster or fibreglass. As these surfaces are designed to remain damp, it is not recommended to empty these pools in the middle of summer as the pool surface can dry out and crack. So it is better to empty the pool in autumn or winter. Also it’s too hot in summer to re-plaster, paint or restore your pool.
Where are You Draining the Water?
Inground pool contain lots of water so you need a water disposal plan before you start draining your pool. You simply cannot pump 60,000 litres of water into the back yard. You must be able direct the water to a storm water drain, the local street drain or a local creek. It’s recommended to not empty your pool when it’s raining as the storm water system is already flooded with water and you run the risk of overburdening the drains.
You cannot direct this water into your sealed sewerage drains as this is illegal and places a huge burden on the sewerage system in your area. Your local city council may have further restrictions and conditions as to when and how you can dispose of swimming pool water.
How to Drain Water from a Swimming Pool
Firstly, remember to turn off the power supply to the filtration system. You don’t want your pump to automatically activate when the pool is empty.
The best way to fully drain an inground pool is with a submersible electric pump which is put on the bottom of the pool and pumps water through a flexi pipe to your drain.
I have seen some filtration systems that have a valve you can activate that pumps the water from near the hydrostatic valve at the bottom of the pool to the storm water drain.
Most systems have a valve to activate which redirects water from the skimmer box to the drain. This is no good for draining the pool as it will only lower the water to the bottom of the skimmer box and then suck in air. A home handyman will be able to connect a flexi pool hose (the one you use to vacuum the pool) to the inlet pipe in the skimmer box and weight the other end of the hose to the deep end of the pool. You can use the vacuum head as the weight. Now you can use your pump to empty the whole pool. So it’s like vacuuming the pool into the drain until the pool is empty.
It is difficult to drain the last few inches of water with the pump. Simply open the hydrostatic valve by lifting the valve head and let the water run into the ground under the pool. Or you can remove the valve by unscrewing it to the drain the water. When you drain a swimming pool I always recommend to replace the hydrostatic valve because the rubber seal and spring deteriorate over time causing leakage from the pool. The valve simply unscrews from the drain and only costs $20 to $30 to replace.
How Long to Drain an Inground Pool
A small pool will take about 6 hours and a large pool over 12 hours. This really depends on the volume of the pool and what pump you are using. The important thing is to keep monitoring the process. I don’t recommend draining overnight as you may leave the pump to run dry causing damage or you may cause an unexpected flood.
Draining Water from an Above Ground Pool
An above ground pool can easily be removed to another location, stored away or sold when no longer needed. Draining water from an above ground pool is a common practice because the pool volume is relatively small and doesn’t take long to empty and refill.
Why Drain an Above Ground Pool?
Repair or Replace the Vinyl Liner: To replace a liner you need to fully drain the pool. You can make underwater repairs to a liner without draining the water using a good underwater repair kit. However, sometimes it’s too difficult to repair. You will need to drain water down to the repair site or completely drain the pool.
Relocation of the Pool: Obviously you need to drain all water to move the pool.
Clean and Refill: If the water is green with algae and the pool liner is slimy to touch one way to fix it is empty the pool and thoroughly clean the vinyl liner. Refill the pool and balance your water chemistry.
Bad Pool Chemistry: If the water chemistry is so bad with chlorine lock due to excessive cyanuric acid, high pH or high metals it may be easier to replace the water with fresh water than try to fix the pool with more chemicals.
Where are You Draining the Water?
The best way to dispose of the water is to pump it into your storm water drain. You don’t want to create a flood on your property or worse on the neighbor’s property. If you have a large property with sloping land you may be able to drain the pool onto your yard and be able to absorb the volume of water without causing damage to gardens or landscaping. If you are on a small block of land the stormwater drain or street is your best option.
How to Drain Water from a Swimming Pool
There are really only two options.
First use a garden hose to siphon the water out of the pool. This is the slowest method and you won’t get the last few inches of water. This could take all day or let it run overnight.
How to Drain a Pool with a Garden Hose
Second use a submersible electric pump. This will speed up the process and remove all the water right down to the last puddle. I highly recommend using an electric pump. You will get good use out of it when you own an above ground pool.
Clean the Vinyl Liner
When the pool is empty you really need to clean the liner before refilling the pool. Or leave it to dry out if you are dismantling the pool and storing it. Be careful to not leave a liner in hot summer sun as it could damage it.
Draining Water from a Hot Tub
Hot tubs and inground spa pools are easy to drain.
The safest and fastest way is to use a submersible pump to a storm water drain. This should only take 30 minutes.
Some hot tubs have a valve at the bottom of the tub that opens to empty the water. But you better have a hose connected to the drain first.
Many people use a siphon hose to a drain and leave it overnight.
The reasons to drain a spa pool are the same as for an inground pool. It could be for repairs, maintenance or renovation.
Please read our article on How Often Should You Change Your Hot Tub Water
Conclusion
Draining a swimming pool is the best solution if you have to winterize the pool, clean or resurface it.
It’s relatively easy and any competent person can perform the task. I recommend a portable, submersible water pump for the task. These are cheap to buy and will be used many times.
The other option is to have the pool plumbing setup to be able to pump out the water to waste. All you need is a hose from your skimmer box inlet pipe into the bottom of the pool. I have used this method myself many times and it works well.