Low suction on Skimmer

[Nedkelly]

Hi folks, I have an 8m x 4m in ground pool with a sand filter.
i have good preesure in the green range on the pump but the suction on the skimmer is low.
i have also noticed the return jets in the pool on seem to be able to push the surface debris half way down the pool.
I have have checked for leaks and can find none, no bedris in either skimmer or pump baskets and have run out of ideas. Can you please advise?

cheers Trevor

 

[Vtfanatic]

How old is the pool? I had a similar issue a few years back. My pool was built with flex pipe at the skimmer that had collapsed. I had to retrench and run new pvc. Could be something similar with older pools. Do you have another skimmer?

 

[Nedkelly]

Pool is 10 years old, no flexi pipe from skimmer to pump house and no other skimmer.

 

[pooldv]

Welcome to TFP!

Green on the pressure gauge doesn't really mean much. It is pretty generic. What matters is what is the pressure no and what is the pressure when the filter is clean. Clean or backwash the filter when the pressure rises 20-25% above clean pressure.

Please add your pool info to your signature so that we can better help you. More here about how to create a sig and what to put in it, Pool School - Read This BEFORE You Post

Is your pool location in California? That doesn't match IP or the metric measurements.

 

[Nedkelly]

Welcome to TFP!

Green on the pressure gauge doesn't really mean much. It is pretty generic. What matters is what is the pressure no and what is the pressure when the filter is clean. Clean or backwash the filter when the pressure rises 20-25% above clean pressure.

Please add your pool info to your signature so that we can better help you. More here about how to create a sig and what to put in it, Pool School - Read This BEFORE You Post

Is your pool location in California? That doesn't match IP or the metric measurements.

The filter has been backwashed and rinsed and the pressure is sitting at the mark the installers marked was correct for normal operation.

 

[duraleigh]

Welcome to the forum

i have good preesure in the green range on the pump but the suction on the skimmer is low.

Why do you think it is low? It is the same pump and one continuous system. If pressure and flow is adequate into the pool, it has to be adequate out of the pool.

Tell us the pressure in psi at the filter and tell us the symptoms that make your suction "low"

 

[setsailsoon]

Hi folks, I have an 8m x 4m in ground pool with a sand filter.
i have good preesure in the green range on the pump but the suction on the skimmer is low.
i have also noticed the return jets in the pool on seem to be able to push the surface debris half way down the pool.
I have have checked for leaks and can find none, no bedris in either skimmer or pump baskets and have run out of ideas. Can you please advise?

cheers Trevor

Ned,

Are you sure the suction is low? Reason I ask is the suction provides the water that produces the pressure after your pump exerts some force on it. If your pressure is good that would mean the suction is normal unless there is a valve that's open that can cause recycle around your pump. That's not likely but you may want to check.

I hope this helps.

Chris

 

[Nedkelly]

Ned,

Are you sure the suction is low? Reason I ask is the suction provides the water that produces the pressure after your pump exerts some force on it. If your pressure is good that would mean the suction is normal unless there is a valve that's open that can cause recycle around your pump. That's not likely but you may want to check.

I hope this helps.

Chris

Hi Chris, thanks for your time and the rest of the guys to hlep me solve my problem.
the pressure at the filter is 12psi.
The pool jets don't seem to have the power to push any surface debris into the skimmer, the surface water is only disturbed by the jets about half way down the pool.

most surface debris passing the skimmer entrance does not get sucked in.
cheers again to all for your assistance.

 

[duraleigh]

I get it now. That's pretty common with pools. It is difficult to get really good flow into the skimmer to pull off surface debris. How far up the skimmer throat is the water? It should be up 1/3 or 1/2 of the skimmer sidewall.

12psi is fine for your pressure and that is really unrelated to your skimmer issue.

 

[Nedkelly]

I get it now. That's pretty common with pools. It is difficult to get really good flow into the skimmer to pull off surface debris. How far up the skimmer throat is the water? It should be up 1/3 or 1/2 of the skimmer sidewall.

12psi is fine for your pressure and that is really unrelated to your skimmer issue.

The water is up to about 1/2 of the skimmer.

 

[duraleigh]

You may get better skimming if you lower it to 1/3,. That said, it will be marginally better and you SURELY don't want to get too low and start sucking air in through the skimmer.

 

[Nedkelly]

You may get better skimming if you lower it to 1/3,. That said, it will be marginally better and you SURELY don't want to get too low and start sucking air in through the skimmer.

i tried that before coming on this forum for some professional help.

 

[duraleigh]

If we gave you professional help, we would have to charge you for it. We're a group of pool owners sharing advice about the TFP method of pool care.

 

[Nedkelly]

If we gave you professional help, we would have to charge you for it. We're a group of pool owners sharing advice about the TFP method of pool care.

I appreciate that, better to ask those with everyday experience for help.
its great to have a forum like this where you can ask for help from a wide variety of sources.

 

[setsailsoon]

Hi Chris, thanks for your time and the rest of the guys to hlep me solve my problem.
the pressure at the filter is 12psi.
The pool jets don't seem to have the power to push any surface debris into the skimmer, the surface water is only disturbed by the jets about half way down the pool.

most surface debris passing the skimmer entrance does not get sucked in.
cheers again to all for your assistance.

OK Ned, now I understand as well! I thought you meant there was water bypassing the skimmer somehow. Skimmers work as a weir and the level affects the velocity of water going into your skimmer. The higher the velocity the further out from the skimmer box you will see surface debris sucked in. The higher the level the more of the water that gets sucked in below the surface and the surface velocity is actually reduced since the pump flow rate is constant. As your water level in the skimmer is reduced the surface velocity increases. There is a limit to how low you can go though since at some point you can't get the sufficient water flow to meet the suction requirements of the pump and you will start sucking air. The size of the skimmer opening should match your pool pump volume so you get sufficient velocity at 50% level. It's possible your pump was replaced at some point with one that has too low a flow. Can you tell us your pool volume and pump flow rate or make and model number?

Do you have a suction side cleaner or did you add one recently? Could be too much flow is going through the cleaner. All of this water bypasses the skimmer box and definitely reduces surface velocity

One possible solution would be to block off part of the skimmer box with a piece of plastic covering part of the opening at one end. You could experiment to get it to the right amount. If that solves the problem you can try something more permanent.

On our pool I do notice increased surface debris when any of the following conditions happen:

• A lot of rain and pool level goes up.
• Wind blowing away from the skimmer box
• Too much suction is coming through the suction side cleaner

I hope this helps.

Chris

 

[Nedkelly]

OK Ned, now I understand as well! I thought you meant there was water bypassing the skimmer somehow. Skimmers work as a weir and the level affects the velocity of water going into your skimmer. The higher the velocity the further out from the skimmer box you will see surface debris sucked in. The higher the level the more of the water that gets sucked in below the surface and the surface velocity is actually reduced since the pump flow rate is constant. As your water level in the skimmer is reduced the surface velocity increases. There is a limit to how low you can go though since at some point you can't get the sufficient water flow to meet the suction requirements of the pump and you will start sucking air. The size of the skimmer opening should match your pool pump volume so you get sufficient velocity at 50% level. It's possible your pump was replaced at some point with one that has too low a flow. Can you tell us your pool volume and pump flow rate or make and model number?

Do you have a suction side cleaner or did you add one recently? Could be too much flow is going through the cleaner. All of this water bypasses the skimmer box and definitely reduces surface velocity

One possible solution would be to block off part of the skimmer box with a piece of plastic covering part of the opening at one end. You could experiment to get it to the right amount. If that solves the problem you can try something more permanent.

On our pool I do notice increased surface debris when any of the following conditions happen:

• A lot of rain and pool level goes up.
• Wind blowing away from the skimmer box
• Too much suction is coming through the suction side cleaner

I hope this helps.

Chris

Thanks Chris,
Lots of great info in your post so I am going to do some experimentation on the skimmer entrance to see what affect it has. The pump is the oringinal from the pool installation an nothing extra added since.
thanks for all great insights.
Ned

 

[edavis]

Did you come up with a solution? I am experiencing similar situation.