Flow under 10 gpm in Filter mode vs 50 gpm in backwash

[mas985]

So it’s either that valve that’s too tight, or the connection to the inlet?

Correct!

The spring side of the bypass valve should be on the inlet side of the manifold. If reversed, the valve will not open.

From the pics & vids I could not tell if it was reversed.

One thing you could try is to just remove the bypass valve (temporarily) and see if everything works.

 

[Joberg]

Correct!

The spring side of the bypass valve should be on the inlet side of the manifold. If reversed, the valve will not open.

From the pics & vids I could not tell if it was reversed.

One thing you could try is to just remove the bypass valve (temporarily) and see if everything works.

I should have tried your suggestion earlier. I received the new valve, it’s also pretty stiff, so I decided to completely remove the bypass valve and the flow is still restricted to 20 GPM at 3250 RPM (I would expect 2x more at least):

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So clearly something up with my heater’s internals. Either there’s massive scaling, rust, or it’s not large enough for the flow I need? Any advice how I can debug this further?

 

[mas985]

With the bypass removed, water should not even go through the heat exchanger. Have you looked inside the manifold for anything broken or loose? Is filter pressure still high on full speed without the bypass valve.

 

[Joberg]

With the bypass removed, water should not even go through the heat exchanger. Have you looked inside the manifold for anything broken or loose? Is filter pressure still high on full speed without the bypass valve.

You’re right, I disconnected the output of the heater to make sure there isn’t something else getting in the way on the return line:

https://youtube.com/shorts/3MCAxvpZJXo?feature=share

As you can see, I now get a healthy 50 GPM coming out of the manifold. When I connect the line back to the heater, the flow drops down to 20 GPM at 3250 RPM (15 GPM at 2200), it’s still better than 8-10 GPM. So when the bypass valve is on, I lose 2X flow, and there’s another 2x loss in the return line which explains why 40-50 GPM drops to 8-12 GPM when everything is connected properly.

So it feels like I need to replace my heater. And fix something in my return line (60 years old pool).

Since we’re renovating the pool area, I’m tempted to ask the pool company to create a new return line + pool outlet in my existing pool and forget about this line. Bad idea? Is it doable?

Another option is to do nothing. Let the pump priming disabled and deal with 8-10 GPM?

 

[mas985]

How many returns do you have into the pool? What size is the eyeball?

When you had the the heater inlet disconnected, what was the flow rate at 3250 RPM?

 

[Joberg]

55 GPM at 3250 RPM when the heater is disconnected.

To be clear, my pool is really old , the eye hole is about 0.75 inches, and I have only one return.

Here’s a video showing first the return to the pool, and next the “skimmer” line with no skimmer (I’m actually 3D printing an insert to prevent entrapment on this line). I bought a small endoscopic camera to see if I could inspect the lines:

I know it feels “clown town” but the pool came with the house. As you can see, the tubing is all metal (copper?), and it looks like there might be build up in there as well.

 

[mas985]

55 GPM at 3250 RPM when the heater is disconnected.

So 55 GPM with the inlet disconnected and 50 GPM with the outlet disconnected?

I don't think the heater is the issue. I just think you have very restrictive plumbing to and from the pool. Even at 50 GPM on backwash at 2700 RPM, the operating point indicates very high suction side head loss (55'). For a typical pool with 1.5" plumbing and your filter type, I would expect an operating point of 94 GPM @ 44' of head @ 2700 GPM. The copper lines may not even be 1.5", then could be as small as 1.25" which would explain the very high head loss. The return side seems to be the same. A single 3/4" return outlet has a LOT of head loss which would also explain why the flow rate decreases a lot when connecting the full return line.

Honestly, I am not sure there is a low cost solution to this problem. The suction lines and returns lines should be replaced with something reasonable or you may never get this pool to work properly.

 

[Joberg]

So 55 GPM with the inlet disconnected and 50 GPM with the outlet disconnected?

I don't think the heater is the issue. I just think you have very restrictive plumbing to and from the pool. Even at 50 GPM on backwash at 2700 RPM, the operating point indicates very high suction side head loss (55'). For a typical pool with 1.5" plumbing and your filter type, I would expect an operating point of 94 GPM @ 44' of head @ 2700 GPM. The copper lines may not even be 1.5", then could be as small as 1.25" which would explain the very high head loss. The return side seems to be the same. A single 3/4" return outlet has a LOT of head loss which would also explain why the flow rate decreases a lot when connecting the full return line.

Honestly, I am not sure there is a low cost solution to this problem. The suction lines and returns lines should be replaced with something reasonable or you may never get this pool to work properly.

Its fine, I have contractors already renovating the whole area. I’m wondering if I could just add an extra return line versus changing existing one? I would like to know if it’s a bad idea to retrofit new return lines or if it’s doable?

 

[mas985]

If you are already adding lines, replacing the old ones should not be that much more difficult. But I would not continue to use copper pipes. It will just continue to stain the pool surface.

 

[CountryBoy19]

Edit: NVM, I thought I had read to the end when I hadn't.

 

[Joberg]

If you are already adding lines, replacing the old ones should not be that much more difficult. But I would not continue to use copper pipes. It will just continue to stain the pool surface.

Do you consult by any chance? You’ve been the most helpful compared to our local pool guys. I’m happy to get on a zoom call, and potentially fly you over and pay for your time if you think you can help me draw an extra return line. I can help, and find hands to do the work. I just need the brains to help with the project.

 

[mas985]

I don't think any of that is necessary but are you planning to do the work yourself? You will need to trench from the equipment to the pool and around the pool. You will want at least 2 and better to have 4 return lines. I would also put in a real skimmer with 2.5" suction lines. This is a lot of work and will require ripping up the concreate around the pool. You may be better off getting a pool builder to do the work.