It was recommended to me to use high temp unions for installing a new pump. How is that different from a Schedule 80 union and is it necessary.
High temp union
- Thread starter Tapio
- Start date
Who's recommendation? High temp unions might be a good idea when going into a heater but shouldn't be required when going into the pump. Well installed Schedule 40 is enough and rated up to temperatures of 140 F.
Edit: Also on your other thread on glue, just use standard PVC/CPVC primer and cement. Primer is a must. The pool-tite seems to be formulated to work better in "wet" conditions during installation but that shouldn't be an issue with plumbing PVC.
Edit: Also on your other thread on glue, just use standard PVC/CPVC primer and cement. Primer is a must. The pool-tite seems to be formulated to work better in "wet" conditions during installation but that shouldn't be an issue with plumbing PVC.
- Jun 22, 2014
- 47,729
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Just to piggy-back to what Joel just posted, I got some additional info and learned some new stuff 
: Each one (40 versus 80) has its benefits in different applications. Schedule 40 pipe has thinner walls, so it is best for applications involving relatively low water pressure. Schedule 80 pipe has thicker walls and is able to withstand higher PSI. This makes it ideal for industrial and chemical applications. For example, 1” schedule 40 PVC pipe has a .133” minimum wall and 450 PSI, while schedule 80 has a .179” minimum wall and 630 PSI. Typically, schedule 40 is used on residential pool applications. It's pressure and temperature ratings are sufficient in just about every application. CPVC (Chlorinated polyvinyl chloride) piping is actually what is designed with a higher temperature rating. Some people may use schedule 80 "CPVC" at the pump in case the pump looses prime and/or overheats, but even that is not guaranteed to be advantageous. It is not uncommon to see schedule 80 "CPVC" anywhere from a couple of inches to two feet after a heater because it can handle the higher temperatures, but if you check the output temperate of the water from the heater, even then it may not really be required. The majority of pools are plumbed with regular schedule 40.
: Each one (40 versus 80) has its benefits in different applications. Schedule 40 pipe has thinner walls, so it is best for applications involving relatively low water pressure. Schedule 80 pipe has thicker walls and is able to withstand higher PSI. This makes it ideal for industrial and chemical applications. For example, 1” schedule 40 PVC pipe has a .133” minimum wall and 450 PSI, while schedule 80 has a .179” minimum wall and 630 PSI. Typically, schedule 40 is used on residential pool applications. It's pressure and temperature ratings are sufficient in just about every application. CPVC (Chlorinated polyvinyl chloride) piping is actually what is designed with a higher temperature rating. Some people may use schedule 80 "CPVC" at the pump in case the pump looses prime and/or overheats, but even that is not guaranteed to be advantageous. It is not uncommon to see schedule 80 "CPVC" anywhere from a couple of inches to two feet after a heater because it can handle the higher temperatures, but if you check the output temperate of the water from the heater, even then it may not really be required. The majority of pools are plumbed with regular schedule 40.
Glad you mentioned wall thickness, Pat. This may not be the case here but many adapter fittings that come with pumps are designed to allow 1.5" SCH 40 PVC to slide inside the fitting and 2" SCH 40 PVC to slide over the fitting. SCH 80 1.5" PVC would not likely slide inside that provided adapter due to increased wall thickness.
For installing a pump, the best unions are the kind that have a threaded fitting on one end with an O-ring (in addition to the O-ring inside the union connection). That allows sealing it to the pump without tape or other thread sealant (which, in many peoples' experience doesn't work well because many pumps have straight threads that don't properly seal against tapered fittings).
Like these: Amazon.com: 2 PACK -CMP Hi-Temp Union 2 Garden
All of the ones I've seen are listed as "Hi-Temp unions", which may be why that's what whoever recommended them used that term, but it's the external thread/O-ring that's the key feature for pump connections.
Like these: Amazon.com: 2 PACK -CMP Hi-Temp Union 2 Garden
All of the ones I've seen are listed as "Hi-Temp unions", which may be why that's what whoever recommended them used that term, but it's the external thread/O-ring that's the key feature for pump connections.
I think the other posters covered things pretty well.
In a nutshell, you have Sch 40 and 80 (there are others, too) and they differ in wall thickness.
You also have CPVC and PVC and they differ in temperature ratings. PVC is the lower...CPVC is used for plumbing in your house.
What pump are you getting unions for? I used this one for my IntelliFlo.
[EDIT] Doh, I see the above poster beat me to it. And yes, good call on the pump's straight threads. Lottsa people, moi incuded, use pipe nipples to connect to the pump. Pipe nipples are NPT or tapered threads. They will seal but they again they may not. I used a good pipe dope to seal mine and it is fine but I plan to change to the unions one day when I'm bored. [/EDIT]
In a nutshell, you have Sch 40 and 80 (there are others, too) and they differ in wall thickness.
You also have CPVC and PVC and they differ in temperature ratings. PVC is the lower...CPVC is used for plumbing in your house.
What pump are you getting unions for? I used this one for my IntelliFlo.
[EDIT] Doh, I see the above poster beat me to it. And yes, good call on the pump's straight threads. Lottsa people, moi incuded, use pipe nipples to connect to the pump. Pipe nipples are NPT or tapered threads. They will seal but they again they may not. I used a good pipe dope to seal mine and it is fine but I plan to change to the unions one day when I'm bored.
[/EDIT]Leslie's Pool Supply gives you a 5 year warranty on pump installations so I had them come out and give a bid and it specified the use of hi temp unions. I never asked why. Anyway the installation cost was not worth the extra warranty for me so I am going to do it myself. The 5 year warranty is nice though and better than anyone else gives.
- Jun 22, 2014
- 47,729
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
I suspect that by doing the job yourself, you will be very pleased with the end result. As in many cases, no one seems to give your pool the "TLC" it needs more than you the owner. Good luck on the pump swap.
- Jun 12, 2011
- 3,761
- Pool Size
- 19500
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pureline Crystal Pure 60,000
I think if you look carefully the "5 year warranty" is on the installation, not on the pump. I'm pretty sure the pump gets the manufacturer's warranty, in Pentairs case 3 years.
I would recommend the high temp unions. If the pump runs dry regular schedule 40 can shrink and leak. 1.5" schedule 80 cpvc threaded nipples would also work.
Note: 1.5" schedule 80 pipe has the same outer dimension as schedule 40 pvc. The wall is thicker, but it's the inside dimension that is different. Schedule 80 will work in regular pvc fittings.
Note: 1.5" schedule 80 pipe has the same outer dimension as schedule 40 pvc. The wall is thicker, but it's the inside dimension that is different. Schedule 80 will work in regular pvc fittings.
- Jun 12, 2011
- 3,761
- Pool Size
- 19500
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pureline Crystal Pure 60,000
It certainly can't hurt and they don't seem to cost more. But what is really important is that they seal to the pump body by an O-ring.
Threaded nipples CAN work but might leak since you're using a NPT thread on a straight thread. The reason the unions have that o-ring is to seal against the pump body because the pump threads are straight...not tapered. The union is a straight thread and therefore requires the o-ring to seal properly. I figured this out after using pipe nipples on the pump (with pipe dope) and while mine are leak free, I will change them out with the proper unions one of these days.
Just remember the 'schedule' of a pipe defines its size, wall thickness, etc. so Sch40 and Sch80 work just fine in fittings since the outer diameter is the same.
But if we get into PVC vs. CPVC, then those don't mix or shouldn't be mixed. Just FYI.
Just remember the 'schedule' of a pipe defines its size, wall thickness, etc. so Sch40 and Sch80 work just fine in fittings since the outer diameter is the same.
But if we get into PVC vs. CPVC, then those don't mix or shouldn't be mixed. Just FYI.
The nipples seal well when Teflon tape and sealant are both used. I have never had a problem gluing cpvc nipples into schedule 40 pvc.
You may be right but that is what they repeatedly told me, both a store manager and a field rep when he came out, that they extend the manufacturers warranty. If anything goes wrong with the pump they will replace it. However I never saw the extreme fine print. If anyone is interested I would suggest to check it out again.
Can anyone cite a source for this statement - "many pumps have straight threads"?
I ask because I'm about to repipe my pool equip pad, and ran across this thread while researching. After reading the thread, I went to hayward-pool.com hoping the spec manuals for my Hayward Super II pump would identify inlet and discharge port thread types, but no such luck. Was just about to order the hi-temp union recommended in this thread, and would like to confirm before placing order... will the hi-temp union with sealing o-ring work on either type of thread? (Currently I have a pvc male adapter threaded into my pump's inlet port, but it won't thread in all the way, so wondering if the hi-temp union will thread in far enough for o-ring to contact pump housing and seal...)
Also wondering if same concern applies to pool filters... I have Hayward S244T.
And actually, also wondering if same applies to cast iron sprinkler system pumps? Mine has a very slight leak at the threaded inlet port... not enough to cause an issue under normal operation, but I can hear the leak it if I torque the inlet pvc fitting just right.
Thanks!
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