How to isolate flow-through expansion tank?

sunlight33

I want to install a flow-through expansion tank like Therm-X-Trol ST-5. My question is what valve/device do I need to buy if I want to isolate it for future service. (My boiler system is using the Webstone one but it only has 1/2'' port)

sunlight33

Yes it's for domestic. I was thinking about two ball valves but if I remove the tank won't water inside the tank shoot out?

EdTheHeaterMan

Yes, so add a Tee with a boiler drain that you can connect a hose to, in order to drain off any excess pressure.

So now you need 2 ball valves, 1 Tee, 1 boiler drain, and some pipe nipples (or copper tubing and a tubing cutter) to connect them all together. If you decide on copper, you may need a torch, Flux, Solder, and grit-cloth if you don't own a Pro-Press.

Mr.Ed

The second and third sentences were brought to you as a public service of the

Derheatmeister

Yes..In order for you to be able to remove the tank you will need an additional tee with a boiler drain to relief the tank pressure prior of the removal.
However,this tee cannot be installed in line with the Turbulator since it will defeat the feature of this design and given the proper circumstances you may still have bacterial growth/legionella formation within the expansion tank which could spread throughout the system !
Have you considered using a flow thru type expansion tank instead of the Turbulating type ?
Richard.

SuperTech

Could a stop and waste ball valve be used? 

Derheatmeister

SuperTech said:

Could a stop and waste ball valve be used? 

Yes, but not between the Expansion tank and the Tee.

sunlight33

If I turn off the water supply and open the hot water faucet to lower the pressure, there shouldn't be any water left in the tank because the tank pressure is now higher, this way it won't be a messy job to service it, right?

sunlight33

Derheatmeister said:

Have you considered using a flow thru type expansion tank instead of the Turbulating type ?

I did, but I thought this turbulating type is already better than the other common ones on the market and it's readily available on supplyhouse.

STEVEusaPA

Use the Webstone exp tank valve, 1/2" brass nipple, 1/2" X 3/4" brass coupling, 1/2" plug for the valve. I do this on every oil fired water heater.

Derheatmeister

STEVEusaPA said:

Use the Webstone exp tank valve, 1/2" brass nipple, 1/2" X 3/4" brass coupling, 1/2" plug for the valve. I do this on every oil fired water heater.

We also use the Webstone valves on our expansion tanks,But this configuration will compromise the Turbulating type expansion tank design.

sunlight33

Amtrol tech support told me the design of the turbulator allows some additional length (but should be minimize) from the tee so it doesn't have to be exactly in the path of the water.

Derheatmeister

sunlight33 said:

Amtrol tech support told me the design of the turbulator allows some additional length (but should be minimize) from the tee so it doesn't have to be exactly in the path of the water.

The first Turbulator expansion tanks came to my attention was 8 plus years ago in Germany
We installed one at my brothers home... They did not allow for any distance and needed it be in the path of the tee...Venturi/Scooping design.
1. I don't know how it would be able to function with out being to the flow path.
2. If the Turbulator extends thru the valve...Would it not be sheared off the first time the Valve is closed ?
Maybe they changed the design.

STEVEusaPA

Didn't see it was a tank with a turbulator. I guess the only other solution is 2 valves on either side of the tee with a drain in one of them to take the pressure off.

Derheatmeister

STEVEusaPA said:

Didn't see it was a tank with a turbulator. I guess the only other solution is 2 valves on either side of the tee with a drain in one of them to take the pressure off.

Yes...but one Webstone still could be used on either side of the turbulator type expansion tank.

Sunlight33.. Here a link to the Back Stop 12 A 202 flow tru type in case you are interested.
http://www.backstop.net/pdfdocs/2Portflyer.pdf
Richard.

sunlight33

I realized my confusion when starting this thread, this tank is used for hot water so it's in an open system as opposed to hydronics, so draining is much easier and not a concern at all. But thank you all for your kind help!

sunlight33

If you set the tank pressure 2-3 psi higher than the water pressure then most of the time there shouldn't be any water in the tank, because as soon as people in the house start using water any higher pressure due to thermal expansion will be reduced back to normal level and the tank will push any water out because it's at a higher pressure than the supply, right?

hot_rod

If you use one of the speciality iso valves, be sure it is low lead certified, to be used on domestic water systems.