Why would you trap a honeywell pressuretrol

curk

I manage a small compound of 4 identical 12 apartment brick buildings, we recently replaced the steam, oil fired boiler with burnham gas fired units. The boilers are working fine in two of the buildings, but the other two have had the following issues.

1) one of the buildingr require the boiler to be drained down 2-3 times a day in cold weather to maintain proper water level, the returns are getting warm pretty quickly, so I don't think they are blocked.

2) one of the buildings is having the vents at top of  steam risers on 3rd floor, in bath and kitchen spitting water, but only in the apartment right over the boiler.

I have turned all the pressuretrols down as low as they go, but I noticed that the plumber trapped each pressuretrol with fittings, he came out of boiler with 1/4" nipple, into an inline tee and cap, the branch of the tee pointing down, then with short nipples and 2 elbows he made a trap that he screwed the pigtail in. He is well known in town for doing many steam boiler installations, I just have never seen this before.

I appreciate any insight that you could help me with...