Are union connections not used in hydronics?

Jells

A plumber startled me by saying that unions are never used for heating.  I was bitching about why check valves don't come with union connections like a mixing valve does so they can be swapped out or serviced easily. It's a pain to have to start cutting pipe just to remove a check valve clogged up with deposits.

 So is this true? I put in a run of baseboard across a room once with unions because I thought it might have to come out to work on the walls. Not been a problem in over 20 years.

Larry Weingarten

Hi, Any chance the plumber was confusing normal unions with dielectric unions?

Yours, Larry

Jamie Hall

Used all the time... handy gadgets.

Jells

Larry Weingarten said:

Hi, Any chance the plumber was confusing normal unions with dielectric unions? Yours, Larry

Given that we were discussing the check valves, I don't think so!

hot_rod

There are a few brands of union hydronic checks available. I would only use unions on items that may need service, a mix valve, check valve for example. No need on boilers or indirects, they won’t be reusable when the time comes to break them open anyways

GroundUp

Sounds like you should find a new plumber. Unions are used everywhere by competent hydronic techs. Dielectric unions, not so much becuase they're prone to leakage. Copper sweat unions also tend to leak regularly. But a good old iron or brass threaded union belongs somewhere in nearly every hydronic system. Sometimes I use pump flanges as a union, or the supplied ones on mixing valves and radiant manifolds, but if those aren't enough to allow service, I'll put some threaded ones in.

EdTheHeaterMan

I'm thinking Radiator valves and Radiator 90 bend are on just about every Hydronic Radiator that has been installed since the beginning of time all the way up to now. Baseboard radiators are the only exception to this rule. But there are some cheep plumbers that will solder a convector w/o a union. Time to get that plumber some learning. He can charge more if he is on time and material pricing. More material more profit. Unless he is not that good of a businessman.

EBEBRATT-Ed

Unions are avoided because they tend to leak especially if not aligned properly and a little "never seize" helps a lot.

The other thing is the quality or lack thereof of the union.

Using 300# unions on black pipe is a good idea but cost more $$$ but are much better quality. In the past "Dart" unions were available and they were always quality. Dart is gone but someone bought them out (maybe Anvil) and FW Webb sells them.

For copper unions avoid at all costs the "all copper wroght copper " Unions they always leak and use the brass ones Nibco makes, they are pretty reliable.

You should use a few unions as possible but use them around equipment that is likely to be replaced

Jells

EBEBRATT-Ed said:

Unions are avoided because they tend to leak especially if not aligned properly and a little "never seize" helps a lot.

The other thing is the quality or lack thereof of the union.

Using 300# unions on black pipe is a good idea but cost more $$$ but are much better quality. In the past "Dart" unions were available and they were always quality. Dart is gone but someone bought them out (maybe Anvil) and FW Webb sells them.

For copper unions avoid at all costs the "all copper wroght copper " Unions they always leak and use the brass ones Nibco makes, they are pretty reliable.

You should use a few unions as possible but use them around equipment that is likely to be replaced

So why do they not make brass check valves with integral union connections? It would be both a PITA and expensive to screw separate unions into both ends of the check. My last install I actually used Shark-Bite checks so I could easily swap or clean them.

ChrisJ

https://www.supplyhouse.com/Caleffi-NA51249-1-2-Sweat-Serviceable-Flow-Check-Valve-Low-Lead

https://www.supplyhouse.com/Bluefin-SCS050-1-2-Solder-Ends-Swing-Check-Valve-Lead-Free

JohnNY

With very little exception...
Every radiator is connected with a union or two.
Every steam header 2" and less gets a union.
Most double check valves (watts 9D) are connected with unions.
...to name a few applications.

Jells

ChrisJ said:

https://www.supplyhouse.com/Caleffi-NA51249-1-2-Sweat-Serviceable-Flow-Check-Valve-Low-Lead https://www.supplyhouse.com/Bluefin-SCS050-1-2-Solder-Ends-Swing-Check-Valve-Lead-Free

I saw those, I needed a lead free, spring type 3/4.

ChrisJ

Jells said:

ChrisJ said:

https://www.supplyhouse.com/Caleffi-NA51249-1-2-Sweat-Serviceable-Flow-Check-Valve-Low-Lead

https://www.supplyhouse.com/Bluefin-SCS050-1-2-Solder-Ends-Swing-Check-Valve-Lead-Free

I saw those, I needed a lead free, spring type 3/4.


You needed lead free for heating?

pecmsg

Jells said:

ChrisJ said:

https://www.supplyhouse.com/Caleffi-NA51249-1-2-Sweat-Serviceable-Flow-Check-Valve-Low-Lead

https://www.supplyhouse.com/Bluefin-SCS050-1-2-Solder-Ends-Swing-Check-Valve-Lead-Free

I saw those, I needed a lead free, spring type 3/4.

Why Lead Free? Are they going on potable water or boiler water?

hot_rod

There is no such thing as lead free brass. Low lead brass, the NSF 61 approved for potable water has a % of lead in the wetted surfaces based on weight. So the initial LF lead free is a bit misleading. LL is a more accurate indication. 
The Caleffi spring checks that are shown actually have a stainless steel body

It will carry the NSF- 61 shield logo, by law, if it was lab tested and approved. And the fees associated with it, paid in full🤓