How to Drain Water from Pool After Rain

It is surprising just how quickly a pool can become full and even overflow after a heavy downpour. Where I live, we get virtually no rain for much of the year, but when we do, it really rains, and my pool overflows.

To drain water from a pool after rain, you will either have to:

• use the pool pump on the waste setting on the pool filter valve
• use a submersible pump
• siphon using a garden hose
• or even the very low tech solution of using a bucket

Even if the water level in your pool hasn’t reached the top and overflowed, if it has reached anywhere near the top of the pool skimmer entrances, then you will need to drain some of it back to the correct level, which is roughly halfway up the skimmer.

How to Drain a Pool Using the Pool Pump

How to drain a pool with a sand filter

This is, without doubt, the easiest method I know of letting water out of a pool if you have a sand filter and a multiport valve with a waste setting.

Step 1 – Run out backwash hose

If you have a backwash hose, run it into the area where you want the water to disperse. If your pool waste goes straight to your drainage system, this step is not necessary.

Step 2 – Multiport valve to drain or waste

Set the multiport valve to either the drain or the waste setting but make sure you switch off the pump before you do this if it is running. (Never move the valve with the pump running as this can damage it)

If you have a valve that shuts off water to the waste pipe (I have one on my pool set-up), make sure it is open.

Step 3 – Switch on the pool pump

Switch on the pool pump and then monitor the water level. It should go down quite quickly, so don’t go off and leave it running as if you get delayed. You may come back to a half-empty pool.

Step 4 – Switch off the pool pump

When the water has reached its correct level, which would normally be approximately halfway up the skimmer entrances, switch off the pool pump. Then, set the multiport valve setting back to the filter position and turn the pump back on as normal.

How to drain a pool with a cartridge filter

Step 1 – Switch off the pump

Step 2 – Unscrew the drain plug

Look at the back of the filter. Near the bottom, you will see the drain plug. Unscrew it completely and remove it.

Step 3 – switch the pump back on

Switch the pool pump back on. Water will then flow from the drain hole. Keep the pump on until the water has reached the desired level, then turn it off.

Step 4 – Replace the drain plug

Screw the plug back into the drain hole.

Using a submersible pump

Using a submersible pump (also known as a utility pump) hooked up to a hose is the next quickest way to drain the water from your pool should you need to lower the water level after rain

You just need to connect your hose pipe to the pump, drop the pump into the pool (preferably into the deepest part) and switch on the power to the pump.

You can direct the other end of the hose to a convenient area of your yard or into a drain.

TIP: If you have a vinyl liner, make sure that you lower the pump to the bottom gently, as a sharp edge on the pump could damage the liner.

You can buy a very effective submersible pump quite cheaply. The Wayne (US assembled) VIP50 is a robust, non-clogging pump that will pump 1800 gallons per hour.

Many utility pumps have a floating switch that cuts the motor when the level drops to prevent the pump from running dry and burning out. You won’t need this feature when using a pump to lower the pool level after rain, but it may be useful if you ever want to use it to empty your pool.

Once you have one you may find other uses for it too where this feature might be useful. Wayne also makes a Wayne 57729-WYN1 higher flow pump with an automatic cut-out when the level drops.

Using gravity (and a hose)

If you have an above-ground pool and need to drain some water, gravity is your friend. You can use a hose to siphon off some of the water, or all of it, if it is perhaps at the top of a slope.

The best way I find to siphon water from a pool is:

1. Place the end of the hose into the pool and then turn on the faucet.
2. Keep it running until all the air is pushed out of the end by the water.
3. Now turn off the faucet.
4. Unscrew or pull off the hose and quickly place a finger over the end to prevent too much air from entering or water flowing out.
5. Now take the end with your finger over it to wherever you intend to empty the water and lay it down. Note: This must be below the level that the other end of the hose is in the pool.
6. The water should then start to flow out due to the siphoning effect.
7. When the water reaches the desired level, remove the end of the hose from the pool to stop the siphon.

Using a low-tech bucket

If all else fails, you could use a bucket to drain water from a pool, but I wouldn’t recommend it unless you are very fit and have lots of time on your hands.

It could take as many as almost 1000 buckets to reduce the water level in a 20ft x 40ft pool by 10 inches. That’s a lot of buckets!

Do you need to drain water after rain?

If you have only had a small amount of rain, which has only raised the level by half an inch to an inch, then you probably don’t need to drain your pool. The level will reduce with evaporation by itself.

However, if you have had sufficient rain to raise your pool water level to the top, or even above, the skimmer entrance/s then you need to empty some of the water. With the water this high, the skimmers will not work, so any debris that lands on the pool will either just float there or become waterlogged and sink to the bottom.

Can a swimming pool overflow when it rains?

A pool certainly can overflow if there is sufficient rain. The water must go somewhere, so once it reaches the top of the pool, it will continue to flow out all over your paving, decking, etc.

Sometimes, pool builders install a pool drain near the top of the pool to allow the excess water to flow away to a controlled area (drain, soak-away, etc.), which will prevent it from actually overflowing.

Should I shock my pool after it rains?

It is certainly not necessary to shock your pool after every rain event. If that were the case, then in some areas, you would be shocking the pool many times a day.

Generally, it would only be necessary to shock the pool if you have had a significant amount of rain, particularly if it necessitated draining the excess water.

Once you have shocked the pool and given it time to settle, you should test the water and make any necessary adjustments.

Does rain dilute chlorine in pool?

Certainly, if your pool level increases significantly during heavy rain, that can affect chlorine levels. But rain can also affect your pool chemistry in other ways:

Rain is often acidic, so this can cause the pool’s water’s pH to go down (making it more acidic). For the same reason, rainwater can also decrease the total alkalinity of the pool water.

Heavy rain may bring with it tiny debris particles, in which case the chlorine levels will decrease as the chlorine is used up to deal with the debris.

Related articles

How to drain an inground pool below the skimmer

Should you run a pool pump when it rains?