Pool losing one fourth inch of water at night with Pump and Filter turned Off

A clear glass vase, on the first step in the pool, used to determine if it evaporation or some other kind of leak in the in-ground pool.

A clear glass vase, on the first step in the pool, used to determine if it was evaporation or some other kind of leak in the in-ground pool.

The square, clear glass vase that I used for pool water-loss testing.

The square, clear glass vase that I used for pool water-loss testing.

Recently I had my in-ground pool relined, and the plumbing from the skimmer to the pump and filter was also replaced. A few weeks after I had that done, I noticed that the water level in the pool had dropped drastically. I thought that it could be evaporation because the weather here in up state New York has been really hot. I filled the pool again, turned off the pump (so that there was not too much water movement) and marked the skimmer with a few pencil lines so I could see where the water level in the pool was. After doing that I still noticed that my pool, which doesn’t have a heater or any kind of water fall feature, was loosing about one fourth inch of water, every night, with the pump and filter turned off. After many days of seeing the water level drop, I called up the owner of the pool service that installed the liner, and he came back to take a look. The pool liner is guaranteed, by the manufacturer, for structural flaws such as holes and faulty seams so I thought it might be something like that. The pool man came back, did some different tests, and it was suggested that a diver come in and take a complete look over everything.

The diver came, looked over everything, and he and the pool man felt that there was a leaking problem with the main drain. The pool man said that the diver should plug the main drain and I could continue operate the pool, with no difficulty, so the main drain was plugged.

A few weeks later, another man was working here at my house, as the relining of the pool is just part of the construction that I’m having done. The man was called in to do the finish work on a cement patio that was poured and on a sidewalk that was installed behind my house. The cement man, was also the installer of pools. He gave me the name of another diver, and that diver was called in for a second opinion.

The second diver came, and after two hours of checking every inch of the pool with a sonar device, diving to look over the liner, and pressure testing the piping to and from the pool, he felt it was not a main drain problem, but a leak in the return piping from the pump and filter, back into the pool. He then unplugged the main drain.

After I paid him, and he left, I called up the pool man, and told him of the divers finding, and the pool man was still questioning the second diver’s opinion.

The pool man came back, did pressure testing of the pool’s return piping, and even left the instrument in place for three hours to see if over time there would be a pressure drop…NOTHING.

After paying for two, who are considered, competent divers, and not getting a similar conclusion, I had to do some research myself.

I looked on the internet, and read many different articles on the subject. The writers of the pieces had their ways of doing things, but I still had to modify what they did to fit my situation. Here is what I did…

(1) I turned off the pool pump and filter and waited a few minutes for the water to become still.

(2) I marked the skimmer with a pencil to know where the water line was when I started my testing. (A scotch bright pad can easily erase the pencil marks from the skimmer).

(3) I took a heavy straight sided (wide mouth) clear glass vase (measuring 5 1/2 inch square and 7 inches tall) and placed it on the top step of the pool, close to the end of the step in the sun. You could also use a large clear glass salad bowl, or any other kind of glass vessel that is heavy and has a wide mouth that would easily let evaporation happen.

(4) I filled the vase with water from the pool, to match the water level on the inside of the vase with the water level of the pool. I then ran the pool by day and turned it off by night.

I then started watching, daily, to see if there was any kind of difference between the water level inside the vase versus outside it. From all of the different articles that I read about evaporation in pools, evaporation does not happen that much by day (no matter how hot it gets), but by night. The water in the pool heats up by day, and when the air cools at night the water evaporates. Also, evaporation happens more when there is hot dry weather, versus hot humid weather. Humid air has water in it already, so less evaporation occurs, versus dry air causing more evaporation.

The object of the(my) testing was to see if the water level (over time) in the vase stays equal to the water level in the pool. If the water level drops equally in the vase and pool it is just evaporation. But, if the water level stays high in the vase, and the water level in the pool drops drastically, there is a leak somewhere; and at that point someone should be called in..

My findings, after four ways of testing, and about an inch water loss, in both the vase and pool, was that it was evaporation after all. Being that the pool liner is new, and having all of that work done, it is such a relief to find that out. Interesting thought, that neither of the divers, nor the pool man had me do any kind of testing similar to what I did with the glass vase.

I hope that if you are having a problem with your pool loosing water, this post helps you come to your own conclusion before calling in a diver or some other pool expert. Happy Swimming!

Companion Posts on Fred Gonsowski Garden Home.com
Picking the Right Paint or Siding Color(s) for you Home 10-19-2011,
Choosing the Right Color ROOF for your Home 10-7-2011,
Picking the Color for Your Front Door 1-17-2012,
Cleaning your Tile and Grout with Oxi Clean…Caulking the Tub like a Pro 2-25-2012
Got Grass growing out onto your Sidewalk or Driveway?…Edge it! 8-26-2012,
An Easy Way to get DEW OFF of car windows in the morning 9-22-2012,
Foundation Planting…Laying out Foundation Plants in Front of your Home 9-28-2013,


About fredgonsowskigardenhome

Your eyes deserve to view beauty. I hope Fred Gonsowski Garden Home helps to turn your vision, into a reality.
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7 Responses to Pool losing one fourth inch of water at night with Pump and Filter turned Off

  1. Cheryl De La Vega says:

    Great pool article! Thank you for all of the detail and problem solving.

    • Hi there Cheryl, glad to be inspiring. My pool issue took a lot of joy out of my back yard project. Practically all of the topics I’ve written about, I’ve gone through myself, and cover how I handled them.

  2. Margaret says:

    Wow, you’re quite a good researcher! I can relate to how frustrating it is when there’s a house problem and the “expert” contractors can’t solve it. It just goes to show that the old saying is correct, “When you want something done right, do it yourself”.

    • Hi there Margaret, the problem with all of it is that it is costing money, kind of a lot of money to get no real results from the pros. I’ve used the pool man for years, and I had the first diver come a few times over the years, and everything was OK. With the liner being new, and costly, it heightened the anxiety that the falling water level caused.

  3. West Coast Homeowner says:

    Love your blog! I found you through Pinterest. Did you design your pool or was it there when you bought the house? I would love to read any tips on design or landscaping around a pool? I’m thinking about putting in something but I don’t know where to start.

    • Hi there West Coast Homeowner, the pool was there when I bought the place. The previous owners of my house put in the pool, and had a Mercedes, but let the place run down to nothing. The house was on the market for 2 1/2 years, and no one wanted it, as there was soo much to be redone.

      When it comes to pools, I would suggest to everyone, to forget getting an in-ground one, and buy an above ground pool instead. An in-ground pool raises the tax level of your hours, you have to have it fenced in, and you have to have extra home-owners insurance because of the pool, not to mention the yearly chemical cost, and having the pool opened and closed each year (all the pool pluming blown out and winterized). A pool is nice for a few years, but after a while you will start to not use it that much, and even possibly hate it. If you have an in-ground pool you are stuck with it, but if you have an above-ground pool, and when the “Thrill Is Gone” you can throw it away. Think twice, or even a hundred times before spending the money on something that does not really raise the value of your property. A pool, here in the north-east is a luxury, a foolish bragging thing for some folk to talk about, and the season for swimming is really short. One year there were only five warm days for swimming. You might say, a heater will change that, but when the weather is cold, you have to be mostly/completely under water to stay worm. After leaving the heated pool you have to run, not walk, back to the house, as the air is cold. Also, if you are in a bug infested place, at night, mosquitoes bite you face, while in the pool. Also, if you don’t like touching dead animals, don’t get an in-ground pool. I’ve had to take out dead chipmunks, mice, baby rabbits, moles, dead frogs that got pulled into the skimmer, and one time a big black crow fell in and was pulled tail end into the skimmer. How yucky is that.

      Hope my little rant makes you think twice. If you still get an in-ground pool, enjoy it, but I hope you remember what I’ve just written to you. As with all of the topics on my blog, I’ve been there and done that ;-}

      • West Coast Homeowner says:

        Thanks for all the tips! I live in Southern California so the weather is less of an issue for me. Lots to consider.

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