VS Pump speed

[JamesW]

This is an estimate of your current system curve at "A".

"B" is closer to what it should be.

"C" is a really good system.




In this graph, Curve A represents 2-inch, Curve B 1.5-inch, and Curve C represents 2.5-inch plumbing networks.

Your system curve matches the 1.5" plumbing curve, which is not good.

 

[DeanP66]

Yes, you should be able to just unscrew the fittings in the pool and pull out the eyeball.

Check valves restrict the flow of water in only one direction. So when your pump is on, the check valve will open to allow water to flow. They are usually spring loaded. When the pump turns off, the spring closes the stopper inside the valve and won't allow any water in the opposite direction to flow. You'll generally see these after the heater if there is a chlorinator installed to protect the heater from the highly chlorinated water that could backtrack into the heater's heat exchanger and rot it out prematurely. The good check valves are serviceable. They usually have about 8 screws that you can use to repair them by just replacing the guts that go inside (stopper, spring assembly).

 

[mas985]

What are the "check valves"? The part of the pipe that can be unscrewed just before my SWG?

Yes

This would be something inside the heater itself that is restricting flow? What are "multiport valves?

Correct. Multiport valves are on the filter. That is the value you use to change from filter to backwash mode.

Do you mean setting the filter to waste and running the pump to see what my flow rate is? This would eliminate everything after the filter from the equation, right? Or do you mean something else?

Something more involved. For example, there is a union right after the pump outlet that can be disconnected and the temporary pipe (i.e. backwash hose) can be used as a return to the pool. This eliminates all of the plumbing after the pump. So if you set the pump for 20 GPM and the RPM drops significantly from the original setting, then the issues is post pump. You can then add back in the filter, heater, check valve, etc. until you find where the problem may exist. It is a bit involved but will determine the exact location of the excess head loss. This would not be possible without the unions.

 

[KevinBond]

Check the cell to make sure that it is clean.

Do you mean the SWG cell? How will I know if it's clean or not?

Can you put the system in "Service Mode" and then go to the pump control panel and find the flow at the following speeds?

Ok, for "Pump PSI", this would be "System Pressure PSI" from the video linked above? Also, I assume I should have all my ball valves completely open?

 

[JamesW]

Do you mean the SWG cell? How will I know if it's clean or not?

There is a screen at the inlet. Make sure that it is clean and look at the plates.

Ok, for "Pump PSI", this would be "System Pressure PSI" from the video linked above? Also, I assume I should have all my ball valves completely open?

Yes.

 

[KevinBond]

There is a screen at the inlet.

In inlet is where the water goes into it (bottom of it in my pic above)?

Make sure that it is clean and look at the plates.

I'll have to remove it to see this, correct?

 

[JamesW]

 

[JamesW]

What is the part that the arrow is pointing to?

When you remove the cell to check to see if the cell is clean, you can also unscrew the union nut at the part to see if there is anything stuck in it.

It's probably a check valve.

There should be a part number, model number and manufacturer stamped on the part.

 

[needsajet]

Hey Kevin, have you ever tried reducing the pump setting down to the point where you can tell that the SWCG stops working? I'm wondering what the intellicenter "thinks" your flow rate is at that point.

 

[JamesW]

This would be a good system curve.

Formula H = 0.008F^2



Yours is below.

Formula = H=0.04444F^2

0.04444 ÷ 0.008 = 5.555.

So, your system is about 5 times more restrictive than is ideally should be.

plot y=0.04444x^2, x from 0 to 60, y from 0 to 100 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

Your TDH at 30 GPM is 40 feet of head (17.3 psi), which is too much.
Your TDH at 3,450 is going to be about 86 feet (37 psi system pressure) at about 44 gpm.

 

[needsajet]

So, your system is about 5 times more restrictive than is ideally should be.

This ratio makes me think it's something other than the combination of components, fittings and pipe.

I wonder if the pump is not sensing GPM correctly, especially considering there seems to be plenty of flow to perform the intended functions.

If there was not enough flow for the system to work properly, I would wonder about a blockage somewhere.

 

[KevinBond]

Wow, thanks so much for all the great advice and things to try! I'll be able to get try most of these things later today.

What size eyeballs are used

They are 3/4".

 

[mas985]

How about the filter pressure at 3450 RPM? What is the flow rate you get at full speed?

One of the issues that you may be experiencing is that the lift for that pump is quite high at 6'. At that lift, that pump will probably not prime unless at close to full speed. If there is a lot of air mixed in with the water, then the pump will be at lower load than normal so it will appear as though the head loss is quite high when in fact it is just that there is too much air mixed in with the water. This will reveal itself at higher RPM.

 

[KevinBond]

Check the cell to make sure that it is clean.

Pretty sure it is clean, here are some pics:

Can you put the system in "Service Mode" and then go to the pump control panel and find the flow at the following speeds?

RPM	Filter PSI	Pump PSI	GPM
1500	4	7	11
1725	5	9	18
1925	9	12	25
2350	13	18	36
2730	19	24	44
3110	24	30	52
3450	30	37	60

Something more involved. For example, there is a union right after the pump outlet that can be disconnected and the temporary pipe (i.e. backwash hose) can be used as a return to the pool. This eliminates all of the plumbing after the pump. So if you set the pump for 20 GPM and the RPM drops significantly from the original setting, then the issues is post pump. You can then add back in the filter, heater, check valve, etc. until you find where the problem may exist. It is a bit involved but will determine the exact location of the excess head loss. This would not be possible without the unions.

I still have to try this. I should be able to use a hose clamp to secure the backwash hose above the pump.

What is the part that the arrow is pointing to?

Here is all I could see for the model #, etc of this part:

When you remove the cell to check to see if the cell is clean, you can also unscrew the union nut at the part to see if there is anything stuck in it.

Didn't see anything inside, here's a pic:

Hey Kevin, have you ever tried reducing the pump setting down to the point where you can tell that the SWCG stops working?

~1670 RPM/15 GPM is the min to activate the SWG.

How about the filter pressure at 3450 RPM? What is the flow rate you get at full speed?

Filter pressure: 30 PSI, 60 GPM.

 

[mas985]

Your measurements appear to be valid for the pump's display values (i.e. they are on the pump's head curves) so the pump is displaying the correct pressure and flow for the given RPM. The plumbing curve increases with decreasing flow rate which is indicative of the behavior of a check valve so all as expected expect that the plumbing curve even for full speed is still quite high (0.024) so very high head loss plumbing.

I am sticking with my original inclination that the check valve is most likely the cause of the excess head loss. That type of check valve uses an axial spring so they tend to have a lot of head loss. That might be the first thing to bypass if you can. Also, there are some markings on the top of the check valve that might be a model number. DN 50 is jut the size of the pipe in mm.

BTW, I forgot to mention that you don't really need that check valve anyway.

 

[KevinBond]

That might be the first thing to bypass if you can.

Is there an easy way for me to try this?

Also, there are some markings on the top of the check valve that might be a model number.

In the picture? That just says "FLOW" and the arrow. On the ball valves I clearly see model numbers. I'll have to take the check valve off again and give it another look.

BTW, I forgot to mention that you don't really need that check valve anyway.

No? I thought it was to prevent chlorinated water from going back into the heater?

Also, I hear a bit of a rattling near the check valve when water is flowing but I think it's from the heater (it's not on). Could that be anything?

 

[DeanP66]

The check valve is a definite must have when using a chlorinator (tabs) because of the highly concentrated chlorine and acid that can backtrack into the heater's copper heat exchanger and rot it out prematurely. As far as a SWG, most people on this site seem to agree that a check valve is not necessary. I'm not sure I agree though. If your pump and SWG turn off at the exact same time, you could have a similar situation like with a chlorinator. Now, you can remedy this by having the SWG shut off before the pump does and that should alleviate any of the danger.

Even the companies that sell heaters can't seem to agree on whether a CV is needed for a SWG. They all agree that it is necessary with a chlorinator. It's up to you though. Maybe going with no CV may help increase your flow rate quite a bit. Just follow the tip about having your SWG turn off well before the pump does and you should be fine.

 

[mknauss]

If your pump and SWG turn off at the exact same time, you could have a similar situation like with a chlorinator.

A SWCG does not create an acidic stew like trichlor.
There is no need for a check valve between the SWCG and heater.

 

[DeanP66]

Maybe not an acidic stew, but it could still create concentrated chlorine right after the generator that could backtrack into the heater, no?

 

[mknauss]

Maybe not an acidic stew, but it could still create concentrated chlorine right after the generator that could backtrack into the heater, no?

No. The FC level coming out of the SWCG is only a point or two higher than what is in the bulk pool volume.