How should this valve be positioned? Heater bypass

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dsg2003gt

Member
Nov 12, 2022
17
Florida
I tried run run the heater with it wide open but it didnt seem to be getting enough flow, when I tried it closed, the pressure in the filter went up a fair bit. In the end I compromised and set it to 65/35 heater to bypass. Should I just send it all to the heater?

Thank you and happy thanksgiving!🦃
 

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What are you trying to do? What kind of heater do you have? Filling out your signature with your pool specifics helps us help you.

Heaters work best when they have sufficient flow. If you choke a heater off too much it will either not work or work poorly/inefficiently. Filter pressure will always go higher with a heater because they increase the head loss of the plumbing system. If you are trying to heat up a spa, then running the bypass so that all the water goes to the heater is the best approach. Almost all heaters nowadays operate with an internal bypass in their header such that most of the intake water goes straight to the outlet side. This allows heaters to accurately control and mix the amount of hot and cold water together. Using an external bypass doesn’t make that process any better. External bypasses are only needed when you don’t plan to use the heater much or you need to service the heater while the pool is still running.
 
dsg,

Not sure how you tried to position your valve, but to run the heater the handle should be pointed straight left. This forces all the water to go through the heater. You should expect the pressure to go up when you add the heater into the path of the water flow, this is normal.

The bypass is not there so that you can regulate the flow through the heater, it is there, so that in the summer, you can take the heater out of the path of the water flow. If you have a VS pump, it means that you can run it at lower RPMs in the summer with the heater bypassed.

Thanks,

Jim R.
 
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Thank you both. I added the pool details to my signature (need to add the robot).

It was cold (75*) here in Florida last night and I was trying to heat the spa. I know the rest of my valves pretty well, but this was the first time I have touched the heater since the pool was built. The PB just set everything up and walked away, and didn't even connect the Aquacal to the RS6 for control, so I had to figure that out after a few drinks, but in the end I got it all working, it just took a while to heat the spa (probably because I was bypassing 35% of the flow).

One last question if you have time. When running the heater what speed should the pump be on? I can't find any documentation on minimum RPM, but when it is on 3450 the jets pulverize me.
 
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dsg2003gt said:
Thank you both. I added the pool details to my signature (need to add the robot).

It was cold (75*) here in Florida last night and I was trying to heat the spa. I know the rest of my valves pretty well, but this was the first time I have touched the heater since the pool was built. The PB just set everything up and walked away, and didn't even connect the Aquacal to the RS6 for control, so I had to figure that out after a few drinks, but in the end I got it all working, it just took a while to heat the spa (probably because I was bypassing 35% of the flow).

One last question if you have time. When running the heater what speed should the pump be on? I can't find any documentation on minimum RPM, but when it is on 3450 the jets pulverize me.
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You should run the pump at a speed that is comfortable for you. You just have to play with it. Obviously if you run the pump to slow the flow switch (which is really just a pressure switch) for the heater will cut out and turn off the heater. So your minimum RPMs is whatever you need to keep the heater running. If you had a flow meter in the plumbing then you typically want to run the system at 40GPM to keep the heater happy. But if you don’t, then you just have to experiment with it a bit.
 
dsg,

There is almost never a reason to run at 3450... As Matt suggests, just lower it until it feels right for you.

You really can't go too low without the system telling you, so as long as the heater is not complaining of low flow, just set it for how you like it.

Thanks,

Jim R.
 
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dsg2003gt said:
One last question if you have time. When running the heater what speed should the pump be on? I can't find any documentation on minimum RPM, but when it is on 3450 the jets pulverize me.
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Try a pump speed between 1800 and 2400 RPM.

A HP like you have is less sensitive to a low flow then a gas heater. As long as the heater does not throw a LOW FLOW error message then you have enough pump speed.
 
Below is what Aquacal says about Water Flow Rates.

At 3450 RPM your pump can do more than 70 GPM and thus damage the heater.

Be careful turning up the pump speed too high to get strong spa jet pressure while you have water flowing through the heater.

Your builder should have installed a flow gauge with the bypass valve so that you can manage the water flow rate through the heater. Consider adding a water flow gauge to your plumbing.


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ajw22 said:
Below is what Aquacal says about Water Flow Rates.

At 3450 RPM your pump can do more than 70 GPM and thus damage the heater.

Be careful turning up the pump speed too high to get strong spa jet pressure while you have water flowing through the heater.

Your builder should have installed a flow gauge with the bypass valve so that you can manage the water flow rate through the heater. Consider adding a water flow gauge to your plumbing.


View attachment 463606
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One question on this.

Does this mean that while heating only I need to keep it between 30/70 GPM and then after I can turn it back up to let the Venturis bubble a little (because my air blower is insane) or does that mean that while the Aquacal is having water sent to it I cant exceed 70 GPM even when not heating?
 
dsg2003gt said:
Does this mean that while heating only I need to keep it between 30/70 GPM and then after I can turn it back up to let the Venturis bubble a little (because my air blower is insane)
Click to expand...

No.

dsg2003gt said:
or does that mean that while the Aquacal is having water sent to it I cant exceed 70 GPM even when not heating?
Click to expand...

Correct.
 
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Thank you. Last question on this:
1. When the heater is not in operation should I leave it positioned to block the flow to the heater or should i leave it in the position in the attached picture?
 

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What’s plumbed there really isn’t a bypass configuration. In order to have a bypass that lets you take the heater out of service without impacting the pool’s operation, there needs to be at least a check valve on the output line of the heater. The check valve is necessary to keep water from back flowing. See this Wiki Article for a proper description -

Heater Bypass - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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I read that before when I initially tried to figure this out. For the time being is that valve positioned good when not using the heater?

Would this be a good place for the check valve?
 

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dsg2003gt said:
I read that before when I initially tried to figure this out. For the time being is that valve positioned good when not using the heater?

Would this be a good place for the check valve?
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In this position, the water is going into the heater. The handle now is at 9 o'clock, closing off the pipe to the pool. Place the handle at 12 o'clock to bypass the heater. The shutoff door inside the valve is on the opposite side of the handle, underneath the word "OFF."

Yes, it is a good place for the check valve. However, the bottom of the check valve is not flat...it extends down about an inch. If you don't have the clearance between the pipe and the concrete, may have to place it in the vertical section.

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dsg2003gt said:
Thank you. Last question on this:
1. When the heater is not in operation should I leave it positioned to block the flow to the heater or should i leave it in the position in the attached picture?
Click to expand...

In this position you send about 50% of your flow through the heater and 50% bypasses the heater.

With this setting your heater will not get more than 70GPM of water flow.

If your heater does not get enough flow to operate and gives a LOW FLOW error then turn the handle a bit clockwise until the LOW FLOW goes away. The valve setting will depend on the pump RPM. Adjusting the valve that way will let you run the heater with the pump at 3450 RPM and have your jets giving you maximum pressure.

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In this valve position you are putting full pump water flow through the heater. You need to watch your pump RPMS to not put more than 70 GPM though the heater.

Yes, you can put a CV in the lower heater outlet pipe. The CV will not change this discussion. The CV will only make a difference if you need to disconnect the heater or the heater begins leaking and you need to fully bypass it to run your pool.


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In this position, the heater will get pressure but almost no flow, so you risk damaging the heater.

You cannot rely on the "No Flow" indicator to tell you if there is enough flow as the heater only has a pressure switch and not a flow switch.

You can have zero flow and still have enough pressure to keep the pressure switch activated.

The bypass should be at least 1/2 closed at all times and all of the way closed at lower flow rates.

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The Bypass Valve Kit (# STK0135) is the best way to protect the heater from excess flow when you will have different flow rates including flows in excess of the recommended limit.

The bypass is a 5 psi check valve, which opens at 5 psi and this ensures that there is at least 40 gpm going to the heater before the check valve opens based on the head loss chart.

Below is the chart for the Ultratemp, but the Aquacal is probably similar.

There is also a flow switch that can be added if necessary.

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https://www.aquacal.com/wp-content/...9/en-us/Content/Resources/CURRENT/LTP0114.pdf

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https://www.aquacal.com/wp-content/...ls_QS/6 Accessories/Available Accessories.htm

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The amount of flow through the heater depends on the head loss through the bypass.

Even at 130 gpm total flow, the head loss is less than 1 psi across the valve when the valve is all the way open which will create only about 15 gpm through the heater.

So, you would get about 115 gpm through the valve and about 15 gpm through the heater.

When you have two or more parallel paths that start and end at the same locations, the head loss for each path has to be the same.

This self balances the flow based on the head loss graph for each path.

If we assume about 10 to 15% of the water will go through the heater with the valve open, the flow through the heater at 40 gpm total will only be about 4 to 6 gpm through the heater with the valve open and about 34 to 36 gpm will go through the bypass.

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For example, if you have (1) 0.75" pipe at 100 feet long, (1) 1.25" pipe at 100 feet long and (1) 1.5" pipe at 100 feet long all Teed together and you put 110 gpm into the T, the water flow would automatically balance such that the head loss would be equal for each pipe.

The 3/4" pipe would get 10 gpm, the 1.25" pipe would get 40 gpm and the 1.5" pipe would get 60 gpm and the total head loss from the T to the output of the pipes would be 20 feet.

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