Hydronic Expansion Tank Isolation Valve

Captain

Is there a code in the US or Canada that prohibits the installation of an isolation valve between the expansion tank the the system?

leonz

I don't believe so no; plumbing in a ball valve above the expansion tank will allow you to change the tank with out losing boiler water if it becomes water logged from a failure of the rubber disc that expands to accept water and contracts to return water to the system.

You just have to decide how to install the valve as you would need a reducer bushing, 1 pipe nipple, a ball valve, and a second pipe nipple and a second reducer bushing that will allow the threading in of the bladder tank.

You have to buy 2 long pipe nipples for the bladder tank side to allow you to have enough clearance to shut the valve off if needed.

Jamie Hall

I sure hope not. It's the way it should be done, and there are an awful lot of them out there done that way

STEVEusaPA

"...You just have to decide how to install the valve as you would need a reducer bushing, 1 pipe nipple, a ball valve, and a second pipe nipple and a second reducer bushing that will allow the threading in of the bladder tank.

You have to buy 2 long pipe nipples for the bladder tank side to allow you to have enough clearance to shut the valve off if needed..."

Forget all of that. I use this one every time. No fuss, no muss (whatever 'muss' is).



If you're not using the port to bring in make up water, you can just plug it.
When I used to use a ball valve, I would remove the handle and hang it with a zip tie.

archibald tuttle

the thing you can't valve off, obviously, is the pressure relief, which would be damn nice to replace those but too much temptation for homeowner to use it to stop dripping rather than as for service replacement only.

to save space and steps i use 1/2" male-female full port ball valve for this application. i've been getting them from zoro, e.g.:

https://www.zoro.com/alpha-fittings-brass-mini-ball-valve-fnptxmnpt-12-in-86310-08-08/i/G3495256/?q=G3495256

There are some cheap ones out there that aren't full port and i've experience stem weeping but i like the quality of these. most supply houses that i know just don't stock anything like this except in smaller pipe diameters.

Mark Eatherton

These valves are required in the UMC.

ME

ratio

If you go through all the trouble of adding an isolation valve to an expansion tank, be sure to add a drain port on the tank side of the valve, or use the Webstone like @STEVEusaPA mentioned, so you can test the tank fill pressure without having to remove the tank!

archibald tuttle

ratio,

in the NFN department, while it isn't as convenient to completely bleed pressure from a flooded tank, i use the air fill valve for that. I also often use the isolation not for replacing tank but when working on the near boiler piping so it is easier to relieve pressure without having to bleed as much water for other work. and haven't found it that daunting - albeit all the installations i work on are in unfinished basements - to get a failed tank off without drowning myself

that said, it looks like its only a few bucks more for the completely tricked out webstone 41672 pictured so unless i have really tight space and need the most minimal solution, i thank steve for posting that as i will start to stock those and use them.

Tinman

It's foolish to not use one. Draining the system to check tank pressure is one of the reasons tank pressure doesn't get checked.

archibald tuttle

i check tank pressure by checking the air pressure in the bladder. i do believe physics suggests that the air pressure will be equal to the water pressure. at least once the water pressure in the system is equal to or above tank pressure, and if it is below tank pressure it would be more or less equal to water pressure in the system if not circulating or to a gauge close to the tank if it is circulating, whether isolated or not. and checking the pressure on the air end usually shows whether you have water passing the bladder.

SuperTech

As a service technician I believe in having isolation valves on everything. If I replace a tank for a customer I always add a ball valve. I'm going to get a few of those webstone valves, they look nice.

I have isolation valves on all my boiler components. The circulator pump, air vents, fill valve and backflow preventer. Anything you might have to replace should be isolated. That's the way boilers should be installed. But unfortunately most installers don't care about the guy who has to work on the system when there's a problem.

hot_rod

On our solar pump stations we supply a double check on the expansion tank. Un-screwing the tank, at the proper connection , the middle union nut, allows one check to keep pressure in the tank, the other to keep the system checked. It's a 3/4 BPSP thread unfortunately.

So you can remove a failed tank and take it outside to relieve the pressure. Or check pre charge easily.

We also sell single checks for expansion tanks, it maintains system pressure when you remove the tank. Screwing the tank in pushes open the check. But you would still get wet removing a water logged tank


https://www.caleffi.com/usa/en-us/catalogue/expansion-tank-connection-kit-255007

archibald tuttle

i said it wrong at first on tank pressure check. while i think i like the webstone (sorry hotrod, gotta go with the 1/2" although yours is handy if the near boiler piping doesn't support the potential weight of the expansion tank). you shouldn't need to bleed the system to check the tank pressure if you can catch the system cold. the whole point is that the tank fill is supposed to be higher than the cold system pressure but lower than the hot system pressure. so if the system is cold the tank pressure is the tank pressure. Of course if you check it hot first and compare your reading to a system pressure gauge that will mildly calibrate your air pressure gauge to the system gauge.

for techs who mostly see the system hot on repair calls though isolation and bleed connection is handy. (although i'm so sick of hooking up hoses to everything i've been piping pex to an open drain - e.g. into a set tub, or i find a place to add a trap and standpipe with a fernco cap with a small hole cut in it to cut down on trap evap, or a sump or . . . on the systems i have to maintain which makes it quite easy and not time consuming to bleed the system down to very little pressure for tank removal but i could also add a tee in this system and pick up a street tee under the isolation valve for the tank so actually the hose outlet on the webstone, upon consideration isn't really what i want. st. tee you say: i love this place where i started getting hydraulic and flare fittings cause they have every friggin fitting i ever wanted:

http://www.discounthydraulichose.com/33750_Brass_NPTF_Street_Tee_p/33750.htm )

clammy

I believe that code applies to portable water expansion even though i have been putting isolation valves ,gauge and drain on my portable expansion tank installs for over 15 to 20 years and never failed a inspection because of it got into fights w bosses over extra fitting cheap **** a close buddy just fail for having one piped this way very recently while in the same town with the same inspector i passed .I always did it for ease of replacement and to make it easy to check house pressure and adjust tank pressure without much hassle .Anyone who does not isolate the wf and expansion tank on a heating system is a tool or does not do any service and does not care usually both but alot of guys dont so they can soak the HO later on labor to bleed and suchon a service call .Human nature totally wacked out peace anf good clammy

archibald tuttle

clammy,

I usually don't put an expansion tank on my portable water, i loosen the cap . . . oh potable . . . . nevermind.

and, more to the point as you pointed out, sounds like an inspector occasionally might fail a valved off expansion tank. you can't lead a horse to water but you can't make him pass the system.

archibald tuttle

BTW, speaking of valving stuff off. I'd still like to see a male female brass spring closed ball valve with no shaft and maybe a big security torx to drive it approved so that pressure relief valves could be temporarily isolated for replacement. maybe it isn't worth the complexity a but they generally are close to as low as you can go on most systems other than the boiler drain and are prone to drip leaks. replace them as much or more as any component. And a lot of the older systems that I see that i haven't brought into the fold yet don't even have isolation of the boiler for that replacement and its often the first thing they need.

hot_rod

i said it wrong at first on tank pressure check. while i think i like the webstone (sorry hotrod, gotta go with the 1/2" although yours is handy if the near boiler piping doesn't support the potential weight of the expansion tank). you shouldn't need to bleed the system to check the tank pressure if you can catch the system cold. the whole point is that the tank fill is supposed to be higher than the cold system pressure but lower than the hot system pressure. so if the system is cold the tank pressure is the tank pressure. Of course if you check it hot first and compare your reading to a system pressure gauge that will mildly calibrate your air pressure gauge to the system gauge.


Actually in the solar business the opposite approach is used, pre-charge the tank a few lbs less then you plan on filling the system to.

Viessmann refers to this as a "safety seal". Since the collector and piping on the rooftop can drop well below indoor ambient the cooling of that portion of the fluid outside causes a decrease in pressure.

Over pressurizing prevents the gauge pressure from dropping to 0 psi. And it prevents call backs as a homeowner see 0 pressure as a leaked system, also.

Of course in solar applications the tank need to be sized for that huge potential ∆. From sub zero to over 300F under stagnation.

The lengthly sizing formula has you assume that wide delta only in the collector fluid capacity, as the piping inside the home and in the HX would not see 0- 300, typically
If you size the whole system capacity for a 300°∆ the expansion tank is massive

Good idea to fill solar to 30- 60 psi to suppress boiling at those high stagnation temperatures tag all collectors experience.

So most solar pump stations have a 90 psi relief valves installed to allow high fill pressure.

leonz

This makes me even happier that I have a steel compression tank in my heating system again(my first one was an open to air expansion tank.hung above the boiler.

Captain

Thanks for the feedback everyone. I've always used Isolation valves on expansion tanks. But just like @STEVEusaPA, I usually remove the handle after installation to prevent accidental closure.

This all started at a trade show a few weeks back when a contractor I was talking with said the code prevents him from installing an isolation valve on the expansion tank. Looking back now I'm guessing he was confused with the potable water expansion tank code just as @clammy suggested.

Gordy

While there is nothing wrong with using steel compression tanks, obviously they have been around for a long time. Diaphragm, or bladder tanks make for a highly successful air free system with proper location of air removal devices, and PONPC. Verses an air “management” system with a compression tank. This type of air management basically involves air moving about the system, and insuring it’s returning to the compression tank. Same basics with PONPC to insure that air gets back where it should be.

bob eck

We have this in 1/2” for expansion tanks and in 1/8” for auto air vents.

Hilly

In Canada under the CSA -B214 require an exp tank to be equipped with a shut-off, that will remain in the open position (obviously) and the handle is to be removed or locked in the open position.

hot_rod

We supply an expansion tank check valve in our boiler trim kits, available in any air separator also. They must be accepted as an alternative to a shut off valve in Canada? We sell a lot of them up there.

The check valve may be a safer option as it cannot be inadvertently shut off.

Mark Eatherton

Yeah but.... Have you ever tried pulling an expansion tank that has pressure on the water side? It is MESSY... I'd prefer an isolation valve with a drain cock on the tank side to release pressure so the diaphragm can be properly checked.

ME

archibald tuttle

hilly, don't you think that is a little over the top. i can see requiring handle removal for an isolation for the pressure relief, or maybe simply the absolutely verboten to have any kind of isolation deal in that case. maybe i could even see that where the boiler is installed without piping the relief to a drain and adjacent to finished space that isolation of the expansion tank should be limited. but some of this is regulatory overthinking. at some point good practice has to take over from rote practice.

bob eck, so it seems like what is pictured is like the check valve of which hot rod speaks. a ball valve that has sat in the same position for a long time can be a liablity in closing. but i wonder how bomb proof that check approach is, and i do like the relief idea although i usually just loosen the tank and let it drip and maybe if i'm lucky locate a strategic 5 gallon bucket. i don't know why i hadn't thought about a tank side relief. now in theory you could have that with a few extra pieces but the single unit seems pretty well thought ought and its affordable (and i guess you could remove the system side valve handle to be canada compliant, no?)