Heater located too far from filter?

[fplouffe]

I am planning to install a heater, either heat pump or gas heater, to my pool. The pool is 8000gl fiberglass, and the pump/filter is about 10' from the pool. Everything is plumbed with 1 1/2" pipes, the pump is 1 1/2 hp and a sand filter.
There is no way I can physically locate the heater near the filter. The best location is about 45' away from the filter.
I have been told by the installer that it wouldn't be a good idea because I would loose to much pressure. He didn't really offer any suggestion how I can make this work which is a bit disappointing. After reading much about head loss and everything, I think he might be right, but I think there is a solution for my problem.
I figured that if I replace the sand filter with a cartridge filter, and thus removing the backwash valve that is a major head loss contributor, and also redo the plumbing between the pump and return line with 2" pipes, I would actually have a lower head loss from pipes/filter/heater than I currently have.
That way, having the heater that far away wouldn't be a concern.

Is that making sense? Would I get away with just going to 2" pipes and keeping the sand filter with it's 1 1/2" backwash valve?

Thanks

 

[Bama Rambler]

Mark (mas985) will have the best answer so maybe he'll see this and drop by. You should probably post the models of your equipment so we'll have a better idea about them.

I'd think if you plumbed from the filter to the heater and back with 2" or 2½" piping and keep the amount of elbows to a minimum you'd be fine with it 45' away. I'd use sweeps (long radius elbows) where ever elbows were required to keep head loss down.

 

[fplouffe]

Thanks. After reading Mark's hydraulic 101 post, I sure hope to get his feedback for my particular problem.

Regarding my equipments:

- Hayward SuperPump SP2610X15 1 1/2 HP
- Hayward sand filter 244T, 24", VariFlo 1 1/2" backwash valve
- Hayward salt-chlorine generator piped inline

I am reading 20 psi on the filter pressure gauge when the filter is clean.

My reading led me to conclude that a good part of the head loss are generated by the filter and backwash valve. The sand filter add around 7-10 feet of head while the backwash could add as mush as 15 feet of head. Unfortunately, I haven't found definitive values regarding head loss for my given equipment.
But my line of thinking was that going with a cartridge filter, I would still have 7-10 feet of head for the filter, but I would regain the 15 feet of head by eliminating the backwash valve. Then, adding around 100' of 2" pipe plus the heater, I wouldn't see too much of a pressure drop in the end.

This sound pretty logical to me and I am trying to convince myself that it's holding ground. I just hope to a confirmation before making a move.

Thanks

 

[Bama Rambler]

If mas985 hasn't stopped by in a while, PM him and ask him to take a look.

 

[JasonLion]

You can certainly do this, even with the backwash valve, if you get everything figured out correctly.

Can you tell us how far it is from the equipment pad to the return jet(s) right now? And how much further would it be if you run the pipe to the proposed heater location?

 

[fplouffe]

Right now, the plumbing is pretty simple. The equipment pad is pretty close to the pool; there isn't more than 10' - 12' of pipe from skimmer to the pump inlet. The filter is right next the pump. The return goes right back to the pool; the salt chlorinator is on the return line. There is 5 spa jet like returns in my pool. There is a 1 1/2" pipe going half way around the pool to each of the jets. From the outlet of the filter to the very last pool return jet, there is no more than 50' of 1 1/2" pipe.
The only location where I could install the heater would mean adding around 100' of pipe: 50' to go from the filter to the heater and 50' to get back from the heater to hook on the return line.

You are saying I should be ok keeping the backwash valve. Wouldn't adding the heater + 100' of pipe increase the head loss too much? I'd like the flow rate to stay as close as possible than it currently is.

Adding the heater, no matter how close or far, would add pretty much the same head loss. It's the 100' of pipe of added head loss that I can't get away with; I am thinking of using 2" for this line since it is significantly better that 1 1/2" even though the rest of the plumbing is 1 1/2".
Since the heater will probably add 10 to 15 feet of head (or more ?), my thinking is to trade the head loss from the backwash valve for the heater head loss.
So in my perfect hypothetical world, the total head loss of my system would only increase because of the 100' of new pipe.

 

[JasonLion]

Alright, let me put that a different way. You can't keep the same flow rate you have now and use the same pump you have now. You can get a tolerable flow rate with your current pump, or get the same flow rate with a different pump.

mas985 is the real expert on this kind of question. Hopefully he will be along soon.

 

[fplouffe]

Thanks Jason. I pm Mark hopping he can join the party.
What is certain is that keeping my current equipment and adding the heater will yield lower flow rate.
So if I understand you correctly, you think I can keep the current sand filter and a going with a higher flow rate pump should maintain the flow rate. Then, you don't believe it's a valid option to keep the current pump and swap the sand filter for a lower head loss inducing cartridge filter that would balance out most of the added head loss from the new heater and then maintaining the flow rate?
Wouldn't it be more cost effective to swap a filter than a pump?


Thanks.

 

[mas985]

Sorry I missed this one. Yesterday was a little hectic.

Anyway, this sounds like an interesting problem and I would be happy to help if I can. You seem to have a fairly good grasp of the issues involved. The extra pipe will definitely have an impact but the amount is dependent on what you currently have.

I can do some predictions on performance but my first attempt put your current filter pressure at around 14 PSI insted of 20 PSI. That ususally means that there is something in the plumbing which is causing more head loss than would be expected. It could be the filter but it could also be a bad filter gauge.

Are you sure the gauge is in good working order and goes to zero when the pump is off?

What size are the eyeball returns (inside orifice): 1", 3/4", etc? To confirm, there are five correct?

Also, is there only a single suction run?

Is the pump much lower than the water line?

Assuming the gauge is correct, I need to add 300' of 1.5" pipe to get to 20 PSI, 41 GPM @ 58' head. If I then add another 100' of 1.5" pipe and a heater (113' of equivalent pipe), I get 22.3 PSI, 36 GPM @ 61' Head. Substituting 100' of 2" pipe yeilds 21.7 PSI, 37 GPM @ 60' of head. So because your current setup has such high head loss, the impact of the heater and extra pipe is much less. But then I would try to figure out why the current setup has such high head loss. Is there a way to bypass the filter and see what the pressure is?

 

[fplouffe]

Hi Mark, thanks for stopping by.

For the sake of brevity, I left out some details that now I realize are more critical than I thought. You are correct about the PSI reading. When the pool was freshly installed and there where nothing but the pump and filter, I was reading 15 PSI. So your model is pretty spot on.

Up here in cold Canada, the pool is medium size but since it's 4' deep all around, it holds only 8000 gl. The pool has 1 skimmer with the main drain through the skimmer so there is only one suction line of 1.5". There is 1 return line of 1.5" with 5 returns. The returns are spa like jets with caps on top of the pool that I can open to get air bubbles in the water jets. The orifice of the return are no more than 3/4" but I would say closer to 1/2". The pump is about 1' above the water line.

The last couple of years, I added the salt chlorinator and solar panels. So the plumbing got a bit more complex with a 3 way valve and some 90 degree bends. The 3 way valve is 1.5" but the rest of the new plumbing is 2" pipes to minimize the head loss. The chlorinator cell is also 2". It's a bit mix and match. I used 2" where all the 90 bends are. The 3 way should be 2" but since I already had it, I didn't change it.

Regarding the solar panel, I have 90' total of 1.5" pipes to get the water to the side of the house and back to the pool. The rise 25'.

I read 20 PSI when the water goes the shortest route: pool->pump->filter->chlorinator->pool. I read 24 PSI when I engage the solar panels: pool->pump->filter->solar->chlorinator->pool.

To make a long story short, I will decommission the solar panel because they aren't effective enough when I need them (spring and fall) and are leaking too often to my liking. My plan is to replace with a heater (gas or heat pump, no decided yet). The location is about the same where the pipes goes up the wall for the solar panels. I could reuse the pipes already there but since they are 1.5" that might not be ideal. The plumbing at the filter might get simpler since the 3 way valve would most likely be removed.

Do you think it could work with the existing 90' of 1.5" pipes? I figured 2" would be better but that involve digging. I can live with that.
Does is make sense going with a higher flow cartridge filter? I am basing myself on reading somewhere that multiport backwash valve can add as mush as 15 feet of head. Is that plausible?

I stop here to not make your head explode

Thanks

 

[mas985]

If the returns are truely venturi jets, then the orifice is likely to be much smaller than 1/2". The 1/2" exit is probably the eyeball but the jet is inside the fitting and you have to remove the eyeball to see it. A standard venturi jet will be either 7/16" or 3/8". If I assume 7/16" orifice, I get exactly 15 PSI so that at least is consistent.

But, I wouldn't expect a few valves and the SWG to add 5 PSI to the pressure. That would now require the equivalent of 200' of 1.5" pipe which is way more than what the 90's and SWG should add. So at this point, I am little stumped as to what would have caused the significant increase in head. Also, I am still a bit confused on what was added to the plumbing that caused the 5 PSI rise. Can you relist in detail every fitting that was added and it's size?

If I can match what you currently have, then I can tell you exactly what will change with the pipe. However, since you are using about the same pipe for solar, the new setup should be about the same as that. The heater will probably be similar to the panels. So if you were satisfied with that, then you will probably be ok with the new setup.

 

[fplouffe]

Strictly speaking of the 20 PSI path, the water get out of the filter from the 1.5" port. This is the pipe/fittings in order:

- roughly 12" of 1.5" pvc pipe
- 1.5" 3 way valve, line flow
- roughly 12" of 2" pvc pipe
- 90deg 2" pvc elbow
- 18" of 2" pvc pipe
- 90deg 2" pvc elbow
- 18" of 2" pvc pipe
- 90deg 2" pvc elbow
- 2" tee, branch flow
- 6" of 2" pvc pipe
- 2" SWG cell
- 2" SWC flow switch
- 2" to 1.5" pvc elbow
- 90deg 1.5" elbow insert, to get into the 1.5" flexible pvc return line.

I am not really happy with the last 2 components; it's a lot of successive elbow and reducer to get from 2" to sub 1.5" flex pvc insert, all in a row.

When I used the charts on http://www.engineeringtoolbox.com, I came up with 1 to 2 feet of head for all of the above with assumed flow rate of 40 to 50 GPM.

The jump of 5 PSI is equivalent to 11.5 ' of head, right? So it leave nearly 10' of head unaccounted for.
Could it be in part due to dirtier filter than when I was running 15 PSI with brand new filter? Could it be because I severely underestimated the head loss of the SWG (I counted as 2' of 2" pipe)? Also, the charts doesn't specify head loss of reducers so I couldn't estimate the head loss of the elbow/reducer combo (I only counted the elbows).

Do you think it's a waste of time/money looking at replacing the sand filter for a cartridge filter? I still think I could reduce the total head loss by 10' to 15' of head by this change.


Thanks,

 

[mas985]

Ok, with the addition of the extra plumbing, I get the equivalent of about 100' of 2" pipe and results in 15.8 PSI, 49.2 GPM @ 52.3' of head. Before it was 15 PSI, 50.7 GPM @ 51.2' of head. So not much of a change and there still is something unaccounted for.

Also, is all of the return line flex and was that there before the changes were made?

Again, are you confident on accuracy of the pressure gauge? They do fail a lot.

Other options, I would open up the filter and check to see if the sand looks good and is not gummed up. Also check the SWG to make sure there is no scaling or something caught in the plates.

However, if you believe the pressure gauge and there is nothing wrong with the filter or SWG, then here is what you might expect with 1.5" pipe:

Current: 20 PSI, 40.1 GPM @ 58.4' of head
Heater: 22 PSI, 35.2 GPM @ 61.1' of head

There is not much of a difference because the existing head is so high. But if your gauge is wrong and the actual PSI is much lower then:

Current: 15.8 PSI, 49.2 GPM @ 52.3' of head
Heater: 19.6 PSI, 41.1 GPM @ 57.8' of head

 

[fplouffe]

Thanks for your advice. I'll opened up the filter next week-end to check it out; I never did. Also, I am not discounting the fact that the gauge might be off. As for the SWG, I checked it 2 weeks ago, it's pristine.
The return line is flex pvc (it's called Carlon I think). It's buried under the concrete walkway. It hasn't change one iota since pool installation. It exits the ground near the filter; so the changes are only between the filter outlet port and this return line where it get out of the ground.

So, worst case, I am looking at 35GPM. Not that bad but I would like to be at least at 40GPM. I can't see where the head loss trouble spot is right now but I'll definitely do more research.

Last thing, I know I am insistent with this, but I would like to either confirm or deny my preconceived idea about cartridge and sand filter. With all else being equal, do you think I would lower total head loss with a cart filter and hence, up the flow rate?

I can't find back the source but I read multi-port backwash valve alone contribute as much as 10'-15' of head. It would be nice if manufacturer publish actual head loss from their equipment.

You are estimating my current head loss at 58.4' of head; could removing the backwash valve bring me down to around 50' of head? That would be a better starting point to add the heater.

Thanks

 

[mas985]

Last thing, I know I am insistent with this, but I would like to either confirm or deny my preconceived idea about cartridge and sand filter. With all else being equal, do you think I would lower total head loss with a cart filter and hence, up the flow rate?

I can't find back the source but I read multi-port backwash valve alone contribute as much as 10'-15' of head. It would be nice if manufacturer publish actual head loss from their equipment.

You are estimating my current head loss at 58.4' of head; could removing the backwash valve bring me down to around 50' of head? That would be a better starting point to add the heater.

Thanks

Sorry about forgeting that piece. Unfortunately, I can't find any data from Hayward on that filter. However, if you compare Pentairs top mount to their cartridge, there is quite a bit of difference. The cartridge has 1 PSI at 50 GPM while the top mount is about 9 PSI loss but a different top mount has about 5 PSI of loss so it does depend some on the filter.

At this point it is hard to know if it is the filter which is causing the high head but then it would have showed up in the old configuration as well. That doesn't mean that a cartridge wouldn't help because it probably would. There might be two issues with the filter. One the normal head loss and two the sand may be clogged.

 

[fplouffe]

Thanks Mark for all your informations. I definitely know more what to look for and what to expect.

I made one mistake when I listed the water path above; the water is actually going the 3 way valve the branch flow path, not the inline flow path. Because of this, there is one less 2" elbow.
The 3 way is Hayward; on the body, there's a head loss spec: .8 PSI max. So that's almost 1 PSI right there from the valve.

Thanks.