Mega press for steam question

RayWohlfarth

I was talking with a contractor installing one of the boilers I sold and asked if he was going to use Megapress He said he would on the large fittings but not on the smaller ones. I thought it was the cost but he said the small fittings are only rated for only 5 psi. Is that true? Are the small fittings only rated for 5 psi

Danny Scully

Negative. 15 PSI. See attached.

Steamhead

Not a good idea to use MegaPress on steam, since it's too easy for the fittings to sag over time. And we know what that causes……………

EBEBRATT-Ed

Bot PP and Mega Press are approved for low pressure steam up to 15 psi.

RayWohlfarth

thanks

offdutytech

I've used 3" mega press for a few repairs on a main. With this job it was the best option to avoid a major project. You have to specify the right fittings and ensure the pipe is supported correctly. It has its place, just not fond of using it for every fitting during a changeout. 2 1/2 and 3" mega press flanges and couplings have saved the day on a few jobs to make the transition to near boiler piping where threading in place would not be practical or increase the cost for the customer by a decent amount.

HydronicMike

You need to make sure you pick the right fitting for the correct application, i.e sealing element, pressure, max temperature.

https://www.viega.us/content/dam/viegadm/download-assets/en_us/tech-marketing/propress/technical-data-sheets/AP-PP-MP-PF_Application_Chart_EN.pdf

AP-PP-MP-PF_Application_Chart_EN.pdf

Steamhead

https://forum.heatinghelp.com/discussion/comment/1865765#Comment_1865765

This is another case of "just because you can, doesn't necessarily mean you should".

RayWohlfarth

I did find this on Viega site. There must be two options

Screenshot 2025-09-23 at 3.46.36 PM.png

EBEBRATT-Ed

I wouldn't use either one on steam if I had the choice.

offdutytech

Agreed on trying to avoid them. I've always used the white dot FKM seal fittings on residential systems. On the handful that I've put in haven't had any issues and the oldest is 4 or 5 years in service. It has its place, but I'd rather cut and thread pipe on steam.