Pool pad plumbing arrangement & thoughts on flexible PVC

MouseMan54

Well-known member
May 18, 2016
99
Riverside, CA
So these questions started in this thread, trying to figure out the right spot to put my SWG. I've settled on putting in the return branch that goes to the pool returns. I'll post pic of my pad later to help visualize. My questions now remain:

1. As noted in the linked thread, I decided to put in a bypass setup for the heater. Was it really worth it for me to plumb in the heater bypass? I decide it was a good idea without much research but the linked discussion has got me wondering if there is really much benefit. My path is already set, as I've already glued those bypass valves in so I can't return them and it would be more work to take them out now. I'm posing the question for my education and future benefit as well as anyone who goes searching for this topic in the future, that others may learn from my experience. (If you think it was a un-needed approach you won't hurt my feelings)

2. When I was looking at @sgoosman 's post here it got me thinking about flexible PVC. That might help me be better able to fit things in. Anyone have any experience/thoughts/recommendation on incorporating it into an equipment setup? I didn't even think of it but I love PEX and flex pipe for tough spots with sprinklers, etc. Something like this?

Thanks for the input.
 
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proavia

LifeTime Supporter
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Feb 6, 2015
1,589
Chandler AZ
1 - heater bypass - when bypassing the heater you have better water flow. Also able to isolate heater if it starts to leak or you have other issues with it. And since yours is already plumbed in...

2 - flex PVC pipe - you could, but why? Flex is more expensive too. Stay with the rigid PVC and schedule 40 fittings, do not use DWV fittings as their glue sockets aren't as deep and they aren't rated for pressure. Also, no real benefit for sweep type fittings either. After we see pictures of your equipment pad, we can give you a few options on how to plumb your SWG, etc.
 

sgoosman

Member
Sep 12, 2018
21
Boonton NJ
Heater Bypass: Totally agree with Proavia. Wonderful idea to have. Biggest challenge for me would be explaining to my wife how to operate the pool heater by pass valves while I'm traveling for work. If you travel a lot like me, you could have that issue but overall the bypass will some day come in super handy so it's money well spent.

Flex PVC- Personally only use it if you must. Flex PVC is bloody expensive around $4-5/ft vs $1/ft for 2" if I remember correctly and then it requires special PVC adhesive, not too expensive but another $10 bottle that is used 1 time... ugg. Flexible PVC has more resistance to flow than rigid PVC. I recall one of my local Lowes sells flex PVC by the foot which maybe then I'd use if necessary but generally I'd avoid.
 

partsman

Well-known member
Apr 28, 2017
210
Westerly RI
The dislike for flexible pvc in this thread is interesting. When I removed my pool from it’s former location, I also took the flexible pvc that the installer used, some was buried. Last year when we installed the pool and I plumbed it all out...I was pressed for time and I used the flex pvc with some rigid and the same primer and cement on both. I didn’t have any issues or leaks at all.
I actually have been working on my pool plumbing the past few days...I changed it up a little this year, but I still used a couple pieces of the flex pvc with the rigid. I was going to take a pic last night when I got done, but it was too dark.

As far as it having more resistance to flow than the rigid...I don’t see how that’s possible because it’s just as smooth on the inside as the rigid stuff.
 

Steve_in_C

Bronze Supporter
Jul 6, 2017
341
Kinston, NC
My opinion is not to use flexible PVC. I have used traditional thicked walled PVC both above and below ground without problems for more than 40 years. If I were going to use flexible PVC, I'd put it above ground so that it could be replaced if it fails. Also tried and true is the original purple primer / PVC cement. The rain or shine blue cement has had some problems. If you are going to bury the PVC I would stay with what has been proven. If it's above ground and easily replaced, it won't make as much difference.
 

ElGood

Member
May 11, 2011
24
Mesquite, Tx
I would think that the flex PVC would offer less of a restriction if you are replacing elbows with a sweeping radius turn using flex, but I'm an old electrician and not an old plumber.
 

MouseMan54

Well-known member
May 18, 2016
99
Riverside, CA
I find it a bit interesting too. If I was coming off a pipe segment and needed to go up and about 4 or 5 inches left over about 2.5 feet of pipe, it seems like it woudl be less restrictive to do that with one gradually curving piece of flex then a 45 and two elbows. It seems as though the logistics of each situation would be a factor. I get the expense, but if it overcomes pipe routing challenges then could it be worth it?

The stuff I linked above is about $3 a foot, says it works with standard fittings, and regular PVC primer and cement. Seems like a reasonable alternative to consider to me. Considering the relatively low PSI of pool systems, I wouldn't be too worried about bursting or failure. That same stuff says it is UV/sun resistant and my pad is in the shade anyway.

As far as primer/cement vs. rain or shine... I've done the primer/clear cement route but I've been using Christie's Red Hot Blue Glue for that last 10 year or so. I've been gluing PVC for 30 years and only ever had a small handful of joints fail. In every case I can remember it was a wet location an I struggled to get the joint dry before gluing. It blew apart as soon as I turned on pressure. I'm fine using the blue glue unless it needs to be inspected and requires primer. Even still, I've never heard of that being called out around here.

I think perhaps those last two things are a "to each their own" kind of deal.
 

sgoosman

Member
Sep 12, 2018
21
Boonton NJ
I don't hate flex pipe and most here don't seem to either. It serves a purpose in a place and time. The interior wall of the flex pvc has the spiral in it which to prevent the hose from collapsing. The spiral either affects the wall the ID of the flex pipe or increases the resistance along the wall in the laminar flow regime. This affects the max velocity by about 3% according to this link: #1 FlexPVC®.com Water Flow Charts Based on Pipe Size (GPM/GPH) ie, How much water can flow through Sch 40 Pvc Pipe Size 1/2" 3/4" 1" 1.5" 2" 2.5" 3" 4" 6" and certainly must have an impact on head loss. Even if now one accounts for it. As others have stated, the ability to gently sweep bends can actually reduce the overall head loss by a greater amount as compared to straight pipe with 90 degree bends.

My avoidance of Flex PVC is more to do with:
  1. Cost, plus often you must buy in 10 foot increments
  2. The need for a specific PVC cement, never seen a flex pipe which did not need a specific flex cement. Not a big expense but who knows!
  3. Lesser structural support
As a DIYer, I will never use the left over flex hose of PVC cement so I'd avoid it. Additionally, I believe welds are easier to make mistakes

Now if you cannot make the connection without flex PVC or it makes your life a lot easier., I fully support using it! Its a tool in a toolbox, just one I try to avoid!
 

markayash

Gold Supporter
Mar 21, 2016
550
Marrietta Ga
I think there is some confusion here..I used 2" FLEX PVC and it's smooth inside and outside and as thick as reg PVC is not thicker..It also used reg glue ( more important to prime ) and loved it..Was it more expensive, yes but i had some pipes that were off set a few inch's and worth it..I bought a roll of 15' and just used the last piece on my last pump replacement.
 

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jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
I think there is some confusion here..I used 2" FLEX PVC and it's smooth inside and outside and as thick as reg PVC is not thicker..It also used reg glue ( more important to prime ) and loved it..Was it more expensive, yes but i had some pipes that were off set a few inch's and worth it..I bought a roll of 15' and just used the last piece on my last pump replacement.
Your picture clearly shows that it is not smooth on the outside, and the same is true on the inside. There are little ridges. But, doing what you did is likely slight lower head loss than the 1 90 degree turn that would have been required.

Also keep an eye on the sweep 90 after your filter, that is a DWV fitting and not the appropriate schedule 40 rated for pressure.
 

Pool_Medic

In The Industry
Apr 1, 2018
1,046
Bangor Maine
Love flex here, yes it stands up in the sun, yes it dramatically cuts down on the use of elbows and couplers. It has had some issues with termites in southern climes but imo it’s as good if not better than rigid. It can move and flex if any ground issues arise, rigid can’t. Some pads with rigid look like they are out of the stone ages when they get complicated and pumps and such need to be perfectly aligned to get unions on. Weld On 795 glue.
 
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markayash

Gold Supporter
Mar 21, 2016
550
Marrietta Ga
Love flex here, yes it stands up in the sun, yes it dramatically cuts down on the use of elbows and couplers. It has had some issues with termites in southern climes but imo it’s as good if not better than rigid. It can move and flex if any ground issues arise, rigid can’t. Some pads with rigid look like they are out of the stone ages when they get complicated and pumps and such need to be perfectly aligned to get unions on. Weld On 795 glue.

I agree, I understand it's not smooth inside but eliminating a 90 is a better trade off :) I am going to redo form the filter out this fall and install a SWG :) I am an old school engine builder so don't like sharp curves.
Did make me think of the " latest greatest" invention the tornado that caused the air to twirl in your intake and get you 75 more MPG and 2000 extra horsepower for just $9.99..But wait!
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
Love flex here, yes it stands up in the sun, yes it dramatically cuts down on the use of elbows and couplers. It has had some issues with termites in southern climes but imo it’s as good if not better than rigid. It can move and flex if any ground issues arise, rigid can’t. Some pads with rigid look like they are out of the stone ages when they get complicated and pumps and such need to be perfectly aligned to get unions on. Weld On 795 glue.
I can provide you with some pictures of flex that did not stand up to the Arizona Sun if you like. So much so that it actually unbonded from the couplers and I could pull them apart by hand.
 

markayash

Gold Supporter
Mar 21, 2016
550
Marrietta Ga
Interesting about the heat issue..
I don't always use primer ( if out ) for normal PVC and never had an issue ( don't try this at home :) ) but I have learned the hard way you have to add it to the flex pipe or it will leak.
Does the flex pipe get soft?
 

Pool_Medic

In The Industry
Apr 1, 2018
1,046
Bangor Maine
Are you certain a flex glue was used? I can show you flex pipe that has with stood 20 years of freezing, thawing and 95 degree weather. Just because you don’t like it doesn’t make it bad.