Skimmers and water levels

[Richakn]

Hi,

Is there anything I can do to improve the performance of my skimmer? I have a floating weir skimmer and it struggles to pull in leaves when the water is at the height my pool guy recommended to keep it. I guess I can lower the water level (in the past when the water level has been lower it has been more effective), but wondered if that's the only solution.

It seems as though the water is higher than the top of the floating weir and therefoe a lot of debris just rests on the top of the water at the inlet (it just seems to get trapped between the water and the top of the inlet) - it doesn't seem to suck it down. The outlet jets seem to be firing and the water 'pull' from the skimmer basket seems ok. The pressure in the system seems fine.

 

[jblizzle]

Can you provide a picture of the water level relative to the skimmer?
Sounds too high if it is above the weir.
Usually the water level should be in the middle of the skimmer opening.

 

[borjis]

I've posted about this a few times.

Some skimmers for whatever reason have been installed in such a way, that the "middle-height" of the skimmer
is not the proper fill level.

Mine is such a skimmer. If I fill to the half point on the skimmer, I get air sucked in and vortexing.
All it needs is about 1/2 an inch more and that is the lowest it can be, so my fill line is about 1 or 2 inches more
to avoid any issues. More of an "upper mid level" fill level.

 

[Richard320]

Think it through. Water seeks its own level.

As the pump sucks water out of the skimmer well, pool water flows into the skimmer well through the throat to maintain the level. So far, so good?

If the cross section area of the skimmer throat is 3"X12", that's .25 sq ft. Let's say the skimmer is pulling a measly 100 gallons per minute. That's 13 cubic feet per minute. That means the flow coming through the skimmer throat will have a velocity of 52 ft/minute to maintain the water level. Now reduce that opening to 1/2"X 12". That's 1/6 the area so to maintain the water level that water is moving six times as fast or 312 feet per minute. That's a pretty good clip - 3.5 miles per hour; enough to overcome slight breezes and currents and pull water into the opening. The weir is critical. The skimmer weir limits the flow coming in to maybe the top 1/2" of water. Less water above the wir means faster current. More water above the weir means sluggish flow.

 

[Jimrahbe]

Rich,

Please show us a pic of your skimmer.. I'm not sure if you have a standard skimmer or some add on skimmer or ????

Thanks,

Jim R.

 

[Richakn]

Photos attached - does this help? It seems like the water is higher (despite being lower than the pool guy told me to maintain it at) than the floating weir.

 

[Jimrahbe]

Rich,

I have not seen that style of weir in a pool before, but it works just like the weir on my standalone spa..

It appears to be working to me... Basically, when the pump sucks water out of the skimmer, the floating weir drops just a little to let more more water in, which also allows any debris to come in...

In general,, the lower the water level, the better a skimmer will work.. the problem is making sure that the water level never goes below the skimmer's mouth..

If this were my pool, I'd see if I could make the floating part a little less buoyant.... Not sure how, but that is what I would try..

Thanks,

Jim R.

 

[Rich D]

Think it through. Water seeks its own level.

As the pump sucks water out of the skimmer well, pool water flows into the skimmer well through the throat to maintain the level. So far, so good?

If the cross section area of the skimmer throat is 3"X12", that's .25 sq ft. Let's say the skimmer is pulling a measly 100 gallons per minute. That's 13 cubic feet per minute. That means the flow coming through the skimmer throat will have a velocity of 52 ft/minute to maintain the water level. Now reduce that opening to 1/2"X 12". That's 1/6 the area so to maintain the water level that water is moving six times as fast or 312 feet per minute. That's a pretty good clip - 3.5 miles per hour; enough to overcome slight breezes and currents and pull water into the opening. The weir is critical. The skimmer weir limits the flow coming in to maybe the top 1/2" of water. Less water above the wir means faster current. More water above the weir means sluggish flow.

Ahhh... That makes sense.. I had not thought of it that way. I have a IFCS and a three way valve that blends the suction lines of the skimmer and main drain. When I wanted extra skimming I was adjusting the three way to almost shut off the main drain thinking the more water through the skimmer the better. This did not seem to give any extra skimming performance. It actually seemed worse then the 50/50 setting I usually run it at. So I just checked and with the main drain almost closed the weir door is laying flat on the bottom of the skimmer so I was pulling in at least 3" of water. I had to throttle the skimmer flow way down to get approx 1/2" of flow over the wier door. I assume these weir doors are designed with a non IFCS pool in mind. I run my variable speed pump at 2950 rpm to get the proper pressure at the heads, So I would assume I would want to throttle the skimmer even lower at these rpms.

Thanks for the great info...

 

[Richard320]

Ahhh... That makes sense.. I had not thought of it that way. I have a IFCS and a three way valve that blends the suction lines of the skimmer and main drain. When I wanted extra skimming I was adjusting the three way to almost shut off the main drain thinking the more water through the skimmer the better. This did not seem to give any extra skimming performance. It actually seemed worse then the 50/50 setting I usually run it at. So I just checked and with the main drain almost closed the weir door is laying flat on the bottom of the skimmer so I was pulling in at least 3" of water. I had to throttle the skimmer flow way down to get approx 1/2" of flow over the wier door. I assume these weir doors are designed with a non IFCS pool in mind. I run my variable speed pump at 2950 rpm to get the proper pressure at the heads, So I would assume I would want to throttle the skimmer even lower at these rpms.

Thanks for the great info...

Maybe you just need more styrofoam on the back of the weir so it floats higher at the higher speeds

 

[Rich D]

Maybe you just need more styrofoam on the back of the weir so it floats higher at the higher speeds

Great point. I will definitely give that a try..