Plumbing for solar

[cactus_LV]

Hi,

So originally my plumbing for solar was supposed to look like the following:

Filter -> Check valve -> 3 Way valve -> 1-solar
2-heater

Unfortunately there wasn't enough space between the filter and the 3 way valve so my plumber did the following:

Filter -> Check valve -> 3 Way valve -> 1-check valve -> 1-solar,
2-heater

With this setup I assume that intake pipe of the solar will never drain because of the check valve which isn't ideal (especially in winter) so I am inclined to remove it. At the same time I don't want the water to drain backwards through my filter and pump back into the pool (when the pump turns off). Is it ok to put a check valve between the pump and filter instead of after the filter (since there isn't enough space to put one) to prevent the water from draining backwards through the filter?

As always your help is very much appreciated!

 

[ajw22]

A CV between your pump and filter will accomplish the same thing as after the filter.

Did your plumber use a solar diverter valve that has a drain hole?

Solar Pool Heaters - Further Reading

www.troublefreepool.com

 

[Ahultin]

So originally my plumbing for solar was supposed to look like the following:

Filter -> Check valve -> 3 Way valve -> 1-solar
2-heater

Unfortunately there wasn't enough space between the filter and the 3 way valve so my plumber did the following:

Filter -> Check valve -> 3 Way valve -> 1-check valve -> 1-solar,
2-heater

My system does not have a check valve between filter and 3 way but it does have a check valve before the solar return tee which it appears you do not. Assuming your plumber used a standard 2" jandy check valve you could swap the inards for a shut off to be used as isolation for future servicing.

 

[cactus_LV]

Did your plumber use a solar diverter valve that has a drain hole?

They did not but based on the description I could drill a very small hole into the diverter to achieve the same result. Is it as easy as that or should I rather buy a new diverter assembly?

 

[cactus_LV]

Seems like the pentair solar valve has a check valve integrated for draining so a bit more sophisticated than just a hole. Is that needed / worth $100?

 

[ajw22]

@Dirk knows more about the solar diverters.

 

[Dirk]

Yep, your check can't go where it is.

You can put that check between the pump and filter (that's where mine is) and it will serve the same purpose as between filter and three-way, which is to keep the drain-down water from the panels from backwashing the filter. That seems a little counter-intuitive, but with the check blocking the flow on the "wrong" side of the filter, it's still going to keep water from flowing into the filter on the other side.

I have a second check, in front of the return tee, as depicted in post #2 above. As that illustration points out, that one is optional. But that check alone would not serve the purpose that the first one needs to. It wouldn't prohibit back-flowing the filter during drain-down.

The check I have in front of my filter is actually a FlowVis flow meter, which doubles as a check valve. I installed that specifically so I could fine-tune the flow rate through my panels. They work best at 40GPM, and with my VS pump and the flow meter I can dial in that rate perfectly.

FYI: A FloVis fits into the body of a Jandy check valve, and you can purchase them with and without the body, so if you already have a Jandy check valve, you can buy just the guts of a FloVis and swap into an existing Jandy check valve body.

If your panels are on your roof, you should have a solar drain-down valve. As you mentioned, Pentair makes one. That's the one I have. Some installers won't bother and just drill a hole into the diverter of a standard three-way valve. I can't speak to whether that works just as well or not. Certainly it would drain as well, but I'm assuming it's passing some water the wrong way, both during solar on and solar off modes. To what extent that is a problem I couldn't say for sure.

My guess would be that you would lose some amount of energy efficiency. If I want to pump 40GPM through my panels and some of the flow is leaking down the wrong pipe through a hole in the diverter, then (1) I would have to goose my pump RPMs by some amount to make up the difference, and (2) some of the water returning to the pool would not have gotten heated. Is that worth a $100 worth of Pentair valve? Someday it will be!

If you already have a Pentair three-way now, I believe you can buy just the drain-down diverter separately. At least I think I saw one for sale the other day, so you could check on that.

Someone here drilled a drain down hole into his diverter, but I cannot now remember exactly what size he tried. I wanna say 1/2", but I can't be sure, sorry. You might try a TFP search for that thread.

 

[Dirk]

If I had money to burn, I'd be tempted to move the existing check to the position in front of the return tee, and then install a FloVis flow meter in front of the filter. Oh, right, that's just what I did! I'm only recommending that because I know that works.

Obviously the FloVis is more expensive than a regular check valve, but I do use it for more than just monitoring the flow through my panels. It backs up my filter's pressure gauge in determining when it's time to clean my filter. I also use it to fine-tune my suction-side vacuum cleaner. And I sometimes make micro flow adjustments throughout the season. As my filter gets dirty throughout the year, flow decreases, which impacts the efficiency of both my solar heater and my vacuum. With a quick glance at my Vis, I can tweak my pump's RPM settings for solar and vacuuming to maintain the perfect flow rate through each, which I then reset after my annual filter cleaning. And it's nice to know my solar heater is doing the most it's capable of, all year long. Again, is that worth an extra c-note? It was to me...

 

[Ahultin]

f you already have a Pentair three-way now, I believe you can buy just the drain-down diverter separately. At least I think I saw one for sale the other day, so you could check on that.

Right now the Pentair solar valve (263047 asin B002FQJ2VU) is on Amazon at $94.95 which is cheaper than the diverter only (270094 asin B004HH1KAQ) at $100.14

I went back thru my notes and I dont have the check valve between filter and first three way since my array is ground mount below pool level. I have a manual drain down at the low point for when it gets cold enough to risk freeze.

Looking at Florida Solar Design groups extensive site, they recommend a 3/16" hole in the three way

 

[Dirk]

Right now the Pentair solar valve (263047 asin B002FQJ2VU) is on Amazon at $94.95 which is cheaper than the diverter only (270094 asin B004HH1KAQ) at $100.14

I went back thru my notes and I dont have the check valve between filter and first three way since my array is ground mount below pool level. I have a manual drain down at the low point for when it gets cold enough to risk freeze.

Looking at Florida Solar Design groups extensive site, they recommend a 3/16" hole in the three way

Yah, I thought I noticed the price of that diverter was crazy high, and I couldn't tell when I stumbled across it if it was just the diverter or the whole valve! I guess it would have value to someone that didn't want to take their plumbing apart to glue in the entire valve, so maybe Pentair charges accordingly.

Ground mount, OK that solves the mystery. I couldn't figure out how you were getting away without that check, but a ground mount doesn't drain-down into the pool, so wouldn't backwash the filter. Though I thought some sort of check was typically used, solar or not, to keep the filter from backwashing into the pool. I don't know much about that, but my plumbing had one there before I installed solar.

I guess the size of the hole determines how long it takes to drain down, right? 3/16" sounds small, but better to start small first.

 

[cactus_LV]

@Dirk thank you so much for the detailed response.
I have a FloVis before the return tee coming from the roof. I am a bit too lazy to remove the check valve so I will probably just remove the flap. Ok I will add a new check valve between the filter and the pump.
I saw the diverter only (270094) on ebay for $60 since I don't want to swap the tee I guess I have to buy that one.
Pentair's website is a bit confusing it states 270094 fits 1-1/2, 2 in. valves but I have 2, 2-1/2 in. valves so I assume it wouldn't fit mine. The only other diverter I found on their website was for 2-1/2, 3 in. valves.

 

[Ahultin]

Inyo lists 270094 as the correct diverter for the pentair 2/2.5 valves
The the pentair 1.5/2 valves are shorter inside so the parts are not interchangeable (tested that theory as I needed a diverter only but found some 1.5/2 valves dirt cheap...didn't work)

 

[cactus_LV]

Perfect than I will go ahead and buy 270094. Thank you @Ahultin !

 

[Dirk]

I have a FloVis before the return tee coming from the roof. I am a bit too lazy to remove the check valve so I will probably just remove the flap. Ok I will add a new check valve between the filter and the pump.

So for the new check valve, just buy a Jandy. Then you can swap the guts of the Vis with the guts of the new Jandy, if you want to. Or swap whenever the mood strikes.

Flow is constant throughout your plumbing system (unless you have some weird bypasses). So the FlowVis will read the same in either location, it doesn't need to be on the solar return pipe to read flow through the panels. The advantage to having it in front of the filter is that you don't have to have the solar system engaged to get a flow reading. Which means when the solar is off, or offline for the winter, you can still make use of the FlowVis. I outlined how I do so previously.

I'm not assuming you don't know this, but FYI: to get a proper reading from a Vis you have to look at it just right, stand on one leg, rub your belly and pat your head. Just kidding. It's easy, but also easy to read it incorrectly. Be sure to understand the correct method, which includes knowing which side of the scale to use (based on pipe size).

 

[cactus_LV]

'm not assuming you don't know this, but FYI: to get a proper reading from a Vis you have to look at it just right, stand on one leg, rub your belly and pat your head. Just kidding. It's easy, but also easy to read it incorrectly. Be sure to understand the correct method, which includes knowing which side of the scale to use (based on pipe size).

I did not know that

The solar tee is a bypass in my mind since I don't have to open it fully and then some water will go up on the roof and some will not that's why I put the FloVis on the solar return pipe instead of a regular check valve.

So for the new check valve, just buy a Jandy

Already ordered a pentair one

 

[Dirk]

The solar tee is a bypass in my mind since I don't have to open it fully and then some water will go up on the roof and some will not that's why I put the FloVis on the solar return pipe instead of a regular check valve.

With the solar valve in "partial mode," you're right, the Vis would have to be on the solar return pipe to get an accurate flow rate thru the panels. But why are you running it that way? Do you not have a variable speed pump? Then it would make sense, to use the solar valve to regulate the flow through the panels. But if you have a VS pump, you want that solar valve wide open and then adjust the flow with the VS pump and Vis. Otherwise, the water that passes straight through the solar valve back into the pool, without running through the panels, is unheated, and that's just a waste of pump RPMs, which is a waste of electricity/money.

 

[cactus_LV]

With the solar valve in "partial mode," you're right, the Vis would have to be on the solar return pipe to get an accurate flow rate thru the panels. But why are you running it that way? Do you not have a variable speed pump? Then it would make sense, to use the solar valve to regulate the flow through the panels. But if you have a VS pump, you want that solar valve wide open and then adjust the flow with the VS pump and Vis. Otherwise, the water that passes straight through the solar valve back into the pool, without running through the panels, is unheated, and that's just a waste of pump RPMs, which is a waste of electricity/money.

I am still waiting for plaster so I am not running anything yet. Initially I thought that maybe I don't run all the water on the roof but as you point out there is no reason to run it partially open.

 

[Dirk]

I am still waiting for plaster

Sidebar: Do you know the "meter trick" to determine the actual water volume of your pool? Pool builder estimates can be wildly inaccurate.

 

[cactus_LV]

Sidebar: Do you know the "meter trick" to determine the actual water volume of your pool? Pool builder estimates can be wildly inaccurate.

I do not know that trick. Now I am curious
I created the plans myself in sketchup and have a rough idea on how much it should be but given the inaccuracies during the build I am sure it's off by a lot.

 

[Dirk]

On plaster day, keep an eye on the crew. They will start your fill the minute they are done (or if you're getting a pebble finish they'll fill the next day, after the acid wash). Just before they start the hose, go out to the street and take a picture of your water meter. While the pool is filling, use as little water in the house as possible: turn off your irrigation system, no laundry, minimize toilet flushes and showers, etc. Then when the pool is full, turn off the hose and go take another picture of your water meter. The difference between the two water meter readings will be your pool's water volume! (Or close enough.)

The less water you use in the house, the more accurate the number will be. Or just subtract: a couple gallons for a flush, 10 gallons for a quick shower, etc. No biggie, the number will be close enough for calculating chemical dosing, and much closer than you or the pool builder can calculate from measuring the pool.