Swimming Pool Blog
by Rob Cox, April 17, 2012
How do I drain my pool?
Some of the reasons for draining an inground swimming pool include:
* Neglected pool, can't see shallow end floor
* Repair or renovation work to plaster or tile
* Acid washing of a plaster pool
* Changing saturated water
Manage a swimming pool long enough, and It's likely that at some point during your pool ownership or management years, you will need to drain the pool. Here's some information on how to safely drain a swimming pool, to avoid any kind of trouble.
Vinyl Liner Pools:
It is considered best practice to try and avoid draining an inground vinyl pool completely. The better method for draining a vinyl pool is to drain halfway, clean very well, and refill. Repeat the process if needed.
The problem with draining vinyl liner pools is that once the water level gets within a few inches of the floor, the liner will relax and pull away from the walls. Especially with older liners, and during cold temperatures, the liner can also contract or shrink slightly without the weight of the water, keeping it in place. This can cause the liner to snap or break while trying to reset an especially fragile liner.
If your liner is fairly new, and not brittle, you can drain the pool completely, but you will need to use a powerful shop-vac or blower box, like the mighty vac, to "re-set the liner". Even so, you may still experience some wrinkling while re-setting the liner - so that's why it's best to not completely drain a vinyl lined pool, but to follow the gradual approach above.
Gunite or Plaster Pools:
It's more common to drain a plastered pool, and many pool owners make it an annual tradition. Here's the steps involved in safely draining your inground pool - to avoid physical damage to the pool and local environmental damage.
General Plaster Pool Draining Tips:
1. Make sure that your pH level is between 7.0 and 8.0 before draining.
2. Allow Chlorine or Biguanide to drop to near zero levels.
3. Pump your pool water far away from the pool (rural areas) or to the storm drain in towns and cities.
4. Don't drain the pool after heavy rainstorms, or if your pool is in a topographical depression.
5. As the water level drops close to the floor, find the hydrostatic relief valves plastered into the floor. Chip the plaster out from inside the plug and use straight pliers to twist open these holes through the floor. This is to allow any hydrostatic pressure under the pool to enter the pool shell. When hydrostatic pressure is extremely great, it can lift a pool out of the ground! To make sure this doesn't happen, locate and open all hydrostats on the floor, as soon as they are exposed. If water comes shooting out like a texas oil well, stop draining the pool immediately.
6. If the pool is very mucky and green, you will want to spray off the gunk as the water level lowers. Otherwise it will "bake" on with the sun and become harder to remove.
How to drain your pool:
1. A small submersible pump, one that can pump at a good rate, can be dropped in the pool - connected to a long hose. Be sure to reach the storm drain, or pump far, far away from the pool. If you don't own a small submersible pump, you can get one at a local rental shop for a small daily fee.
2. Use the filter pump. If you have a separate main drain line, and you can close off the skimmer valves, then you can set your filter multiport valve to "Waste", and drain the water out of the backwash hose. If your pool is not too dirty, but has clear water, you can also do this with a push-pull valve (aka, slide valve). just move the handle to the backwash position and close the skimmer valves.
If you have a cartridge filter, there is no backwash valve, and using the filter pump to drain your pool will be impossible, unless you install a 3-way valve after the pump, to allow for diverting the water out of the system.
If you have what I call "Combination Skimmers", where the main drain is tied into the skimmer, you can also use the filter pump to drain the pool. If you have only one hole in the bottom of the skimmer, you can continue to pump the pool nearly empty by plugging the top of the skimmer with an expansion plug, or a threaded plug with o-ring.
If you see two holes when you look into your combination skimmer, usually front and back - then it is more difficult to pump below the skimmer. The easiest method is to connect a threaded hose adapter into the hole which goes to the pump, and connect a primed, "tight" vacuum hose to it. If you hear air sucking, you can use some duct tape.
If using the filter pump to drain or lower your pool water level, it's important to leave the pump running until it's completely empty. If you shut it off (to go to bed for example), you will likely not catch prime again.
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