Lower flow rate after hayward upgrade?

[Benzee5]

I have an Intex 16x32x52 above ground pool.
I upgrade to a hayward 1091 skimmer. For now, I can move my intake hose between Hayward and O.E. Flow rate is lower with the Haward (according to needle on sand filter).

Doesn't make sense. New skimmer has 1.5" hard plumbing vs the skinny hose of OE.
OH, and only one of the dual intex lines are connected.

 

[mattwm]

I imagine the gauge on the filter is for pressure and not flow. If this is the case, then it makes sense you would have lower pressure considering the upgrade to larger and rigid pipe.

 

[jblizzle]

Welcome to TFP!!!

I think Matt is thinking about that backward and I think I agree with the OP puzzlement.

If you are only changing the suctions side (and the filter is after the pump right? I thought there was some Intex system where the filter was before the pump),
lowering the restriction on the suction side should cause the filter pressure and flow rates to increase.

If the return lines were increased in size, then I would expect that to possibly lower the filter pressure, but the flow rate would increase.

Can you actually feel the return jet and sense a difference?

 

[Benzee5]

The gauge reads Lower is better. With the intex hose connected, the gauge reads in the green, mid to low end (great), with haward, the gauge reads high green. Almost yellow. I'll post pic when reassemble salt system. Its soaking in vinegar now.

 

[Benzee5]

Haward gauge reading plus pic of skimmer (unubstructed)



Intex reading. Only 1 of the dual hoses attached

 

[jblizzle]

It is showing higher pressure with the Hayward. That is what would be expected with lower resistance in the suction line.
Ignore the stupid colors.

All is good.
Nothing to see here.
Move along.

 

[Benzee5]

This morning, there was barely any water flow. I pulled out the skimmer basket expecting it to be clogged and it wasn't.
Next I checked the pressure on the sand filter and it was in the yellow. About 14psi.
So I backwashed and then rinsed the sand filter then the needle went to just above where it is in the pic above. 11psi. Plus there's water flow now.

3psi raise made almost no water flow. I think I should trust that gauge.

With Hayward hooked up, not only is my pressure reading higher, I don't have as much pressure coming from the return. It's noticeable.

This doesn't make any sense to me.

 

[jblizzle]

We recommended cleaning your filter when the pressure raises 20 to 25% over the clean pressure. If you wait much longer than that the flow rate drop significantly, which appears to be what you just observed.

 

[jblizzle]

It just doesn't work the way you're claiming it does. If you have a clean filter and the pressure goes up the flow rate must have increased.

 

[Benzee5]

I cant attach anymore pics but at 10:30am today, I was at 11psi. Water barely flowing.
I switched over to the old and pressure was 5psi. Very good flow coming on return now.

 

[jblizzle]

Would need to get pictures of your entire plumbing setup, but what you are describing is not normal and makes me think you are overlooking something.

To post more/larger pictures, you either need to raise your storage allotment by Becoming a TFP Supporter or follow the How To Post Pictures tutorial ... just avoid PhotoBucket.

 

[Benzee5]

The guy at Leslie's had a great idea. The pump cant handle the new water flow and its choking. He said to try throttle back the flow with the shutoff valve. Find the sweet spot where the pressure will be good. I'll try and see how it does or dont work. If not I'll show pics of plumbing. If this site will let me. Wouldn't accept pics a little while ago. Mb limit

 

[jblizzle]

That Leslie's guy has no idea what he is talking about. That makes no sense from a hydraulics perspective.

See the links in my previous post about adding pictures.

 

[JasonJoel]

Actually what the Leslie guy is saying CAN make sense. It all depends on what the pump curve looks like for that particular pump.

I've seen many times where people had to partly block the outlet to raise pressure to get on a better/more stable part of the pump curve and prevent it from cavitating or stalling.

That being said with what the OP described with high pressure and low flow, I would not think partially blocking the outlet would help

 

[jblizzle]

Actually what the Leslie guy is saying CAN make sense. It all depends on what the pump curve looks like for that particular pump.

I've seen many times where people had to partly block the outlet to raise pressure to get on a better/more stable part of the pump curve and prevent it from cavitating or stalling.

That being said with what the OP described with high pressure and low flow, I would not think partially blocking the outlet would help

Agreed, if the head loss is too low on the pressure side of the pump, there can be cavitation problems.
But the change being made in this thread is about lowering the head loss on the suction side of the pump, which should not cause the same issue.

My understanding of what the Leslies guy was suggesting was to paritally block off the new suction line from the skimmer, which makes absolutely no sense.

 

[mattwm]

I admit this has had my mind boggled the past couple days. A constant speed pump will ride its curve and flow will vary along with system pressure. If THD is reduced ( pump does not care where ) then flow should increase. This is evident when looking at any performance pump curve. Pressure and flow cannot both increase.. this can only happen when more work is done on the system (more rpm). Where am I going wrong?

 

[Benzee5]

Ok. I partially closed valve until pressure dropped. Worked great! You could actually hear it change at the pump. Flow is doing good now. Only took like a 1/4 turn. Well, valve is 1/4, so 1/4 of that lol.

 

[jblizzle]

I admit this has had my mind boggled the past couple days. A constant speed pump will ride its curve and flow will vary along with system pressure. If THD is reduced ( pump does not care where ) then flow should increase. This is evident when looking at any performance pump curve. Pressure and flow cannot both increase.. this can only happen when more work is done on the system (more rpm). Where am I going wrong?

I think you have to consider whether the head loss is on the suction side or the pressure side. If you add loss on the suction side (close the suction line), you will reduce flow and reduce the filter pressure. Alternatively, if you lower the head loss on the suction side (like the OP did by going from a hose to PVC with skimmer), the flow rate and the filter pressure will increase.

If you were to add head loss on the pressure side (say the filter getting dirty), then the flow rate will drop and the filter pressure will increase.

Ok. I partially closed valve until pressure dropped. Worked great! You could actually hear it change at the pump. Flow is doing good now. Only took like a 1/4 turn. Well, valve is 1/4, so 1/4 of that lol.

I just can't in my mind think of why that would have helped. Does the pressure on the filter guage increase or decrease when you closed the suction valve? Remember ignore the stupid colors because they really are pointless.

 

[Benzee5]

Ignore the colors but meanwhile when it in yellow at 11psi, there's barely any flow. When in green at 5-6psi, I have great flow. Which is where it's at now.

 

[jblizzle]

If nothing is changing Downstream of the filter what you just stated is impossible. The only way for the pressure to go up in the filter is if there is blockage in the filter or after the filter or if the flow rate increased.