Bottom Drain Valve And Pool Water Pressure

by Steve

Should you run the main on a in ground pool at half closed?

Does this take away the pressure from the sand filters and put more strain on the pump itself?

Thanks for the question Steve

This might sound like a "foo-foo" answer, but it's not.

Each pool is different, with different needs and requirements. Some pools have many trees and flowering plants for landscaping.

This means more leaves and debris will fall into the pool and stay on the surface.

The skimmer needs to be wide open and the bottom drain can be half way.

Other pools may have no landscaping, but there's alot of dirt around, and let's say the pool doesn't have a pool cleaner like a Polaris.

It has pop-up cleaners on the floor of the pool.

These pop up and move the dirt to the deep end where it gets sucked away through the bottom drain.

In this case the skimmer can be dialed down a bit, but the bottom drain can be wide open.

If your filter is running at a good pressure and your pump has a good prime, you probably have a good balance.

And that's what it's about, a good balance between the skimmer and bottom drain.

There is no hard and fast rule saying the bottom drain valve should be 1/2 way open and the skimmer valve only 1/4 open.

It really depends on what your pool needs for proper cleaning, while having enough GPM to ensure good filtration and proper water flow. A good balance.

Home pools run gallons per minute (GPM) between 20 - 60. Commercial pools run between 240 - 280 GPM.

You can probably go to your local pool store and buy a GPM gauge if you're concerned about it.

I had about 50 pools on my pool route in Arizona and each one was dialed in a little differently.

Hope this answers your question and have a safe and fun swimming season.


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Dec 13, 2017
bottom drain
by: Todd

Have a pool where the pump basket fills up with water fine but when I open the bottom drain valve the water in the basket disappears and the gages on the 2 sand tank drop to to 0 after a few mins water shoots back into the pump basket for a second then disappears again I can shut the valve off to the bottom drains and water appears again and runs fine. What could be causing this

Hi Todd.Pools are a closed system which means air should not get into it. Clogs can also cause the issue you're describing. If you have good prime with the skimmer, then open the bottom drain and the pump loses prime, most often it's a clog in the bottom drain plumbing.

What you can do is to put your multi-port valve to recirculate and open the bottom drain. Recirculate bypasses the filter so you get much more flow. This might dislodge any debris that might be caught in the drain.

Another possibility is to use a water bladder that can be purchased at any hardware store. I have a video on YouTube about unclogging both the skimmer and bottom drain.

You close the skimmer valve is possible, then place the water bladder in the pump pot plumbing which will force water back to the drain.

If these don't work you will need to call in a professional to unclog the system. You could just leave it alone. Bottom drain and mainly to suction the bottom water to be filtered.

Hope this helps.


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Water Not Free-Flowing When Pool Pump Switched On

by Pat Hughes
(Surrey, UK)

This season my pool pump has acted strangely. To begin with, priming the pump at the start of the season was OK but needed quite a lot of water to activate free-flow.

Sometimes when turning the pump on after shut down over night the water has flowed normally without priming, but sometimes after much priming it has "fired" up quite vigorously making the sand filter bubble in a similar way, which has made the water push through at the base in the pool but not sucking the water in through the skimmer at the top.

Now after such an event I cannot get free-flow at all when switching the pump on even after leaving the hose on for some time.

The sand filter, I believe, now needs replacement sand which I am about to arrange, but would this be part of the problem?

The pool does not have a cover over it and it is sited over a very large tree with debris constantly falling into the pool.

Any advice would be very welcome.

Thanks for your question Pat

I have written about problems like this at these posts:


Closed Valve Setting Still Lets Water Through!...Pool Leaking..

Above Ground Swimming Pool Losing Water..Running Sand Filter System..

There could be a variety of problems with the loss of suction from the pool pump.

*Broken, worn, or torn gasket on the pump lid
*Impeller blocked with debris
*Loose pump lid
*Cracked or broken suction lines

Whenever air gets into the system it will create an air pocket in the pool pump. This could be caused by any number of reasons, a few of which are above.

The sand in your sand filter should last anywhere between 5 - 10 years, depending on the amount it's used. More use will equal more frequent changing out of the sand.

Before you replace the sand I would advise you to look inside the filter to make sure there's enough sand. Your owner's manual or contacting the manufacturer can help with that.

Also be sure the sand doesn't need to be de-greased. Squeeze the sand together and if it feels greasy or sticks together, it might need a de-greaser. A good de-greaser is "Filter Fresh" which can be found at any pool store. It's the product I use when the sand filters at the YMCA need to be de-greased.

If after de-greasing you're still not getting the pressure you need, it might be time to change out the sand. You should backwash the filter when the pressure reaches 8 - 10psi over "just backwashed" pressure and stop when the water turns clear. This takes about 1 - 2 minutes.

Make sure you pool water level is correct; 1/3 to 1/2 up from the bottom of the skimmer(s). Too much water and the skimmer won't have enough little water and air will get into the system.

Hope this helps and let me know how it turns out for you

Have a great Summer


Donation..My Pool Guy..

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Above Ground Swimming Pool Losing Water..Running Sand Filter System..

by Karen

Pool liner was just replaced. Pool water level remains constant until the sand filter system is running.

The swimming pool water level drops after a couple of hours to the point where the skimmer isn't getting enough water to do its job.

What is the possible problem?

Thanks for the question Karen

I would first check the obvious:

*Are there any leaks on or around the filter equipment or pad? Look at the filter, pump motor, pipe valves, etc...any piece of equipment.

*Check the ground around the filter and pad for moisture and wet spots

*Is there any moisture around the pool or wet areas? Walk around the pool and the equipment.

*For your vinyl pool liner, look for tears anywhere and everywhere; separation around all the fittings, skimmers, returns, cleaner line, lights, steps and the corners

Use a grease pen and mark an area on your pool, then measure the amount of pool water you're losing. It shouldn't be more than about 1/4 inch per day.

Vinyl pool liners should have water in them at all times, but here are a couple of tests you can do to eliminate some things:

If the pool water level drops, then stops right below the skimmer, the leak is probably is or near the skimmer or the return lines. If the water level drops, then stops by the light, the leak is probably is or around the light.

If you have air coming back through the return lines, there might be a crack in the lines, or the pool filter pump lid or O-ring needs to be adjusted or replaced.

If the pool is losing water while the pool pump motor is running, the leak is on the return line side of the filter system. Take a look through the pump motor lid and check to be sure the pump has a good water supply. If there's alot of air it could be a cracked pipe somewhere.

If the pool is losing water while the pump motor is off, then it's probably the pool itself.

If you do these and you still can't find the leak, then it's best to call a local leak detection business. You might be able to minimize the cost of them coming out by doing a little trouble-shooting of your own and cut down on the hours they're on-site.

Hope this helps and best of luck


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