I work in a 4 story off complex. Multiple restooms on each floor.
Pottable water feed is a 2″ service. City water pressure is between 80 and 90 psi.
After the backflow preventer the service remains 2″, but divides into a header with three sepperate pressure regulators. There are two 2″ line and one 1″ lines coming off of the manifold head, each with and appropriately sized regulator.
Down stream of the regulators the pipes enter a 2″ outlet manifold, then to branch piping to restrooms, showers, water foutins, water heaters, etc.
Pressure at the outlet manifold is about 65 psi, but varies down to a low as 50 psi when there are a lot of fixtures in use.
My assumption is that the three regulators in paralell are to reduce this fluctuation in pressure.
Am I on the right track, or is this just a SWAG, and I am way wrong?
Dave
Replies
So the service line is manifolded to three pressure regulators and then manifolded back together again?
That's weird. Why not use a regulator big enough for the anticipated flow? Maybe one wasn't in stock that day.
Or maybe someone misread a drawing that called for different regulators for each level. With a three-story difference top to bottom, that would be about 30 feet/ 2.31 = 13 psi difference, top to bottom. For that 3-story difference between floors, I'd wouldn't have spec'd separate regulators. If one had 65 psi on the first floor, 52 psi on the fourth floor would be fine.
65 to 50 psi drop seems like too much pressure drop for all those regulators if they are all set them same. But they probably aren't all set the same. If the smallest one if set to 65 and can't keep up, then the next one would open (maybe at 50 psi) when pressure drops to it's setting.
Multiple regulators wouldn't have been put in to reduce the fluctuation, but maybe to deal with pressure drop that would have happened across one regulator. Try turning the screw* on each one during flow conditions to determine which one is set the highest. Bring its setting down, (or the others up) and that should minimize the fluctuation IF the fluctuation is due to the regulators.
But the fluctuation may be due to some other component entirely. A whole-building filter or water softener (THERE'S a reason why someone might have manifolded the outlets together after the fact!). And sometimes the water meter is undersized. I've seen amazing stuff all run through a 5/8" meter. Fire protection water for crissakes! Stupid, stupid, stupid.
*Tying a little string to each regulator adjustment stem will let you keep track of how many times you've loosened or tightened each one (tie the other end loosely to something fixed or a dangling machine nut as a weight). Kind of an analogy counter so you can get back to initial conditions if it all gets too confusing.
Thanks David.
Sorry I didn't get back to you sooner. We had a frost proof sill cock split yesterday. Found it after it had been running 2 1/2 hours, and flooded part of the basement and an elevator pit. Heck of a mess to clean up.
Those regulators are in parralell off of the 2" incoming service, and go back into a common 2" line that then branchs to the various stuff. There are no filters or water softeners. By the time the lines reduce as they go up and get to the penthouse on the roof, I can almost stop the flow from a hose with my thumb. Takes forever to wash the condenser coil for a small pony chiller we have up there. I'll put a pressure gauge on the hose bib and let you know what it reads. We teed into a 1" line to put in the hose bib, thinking that the one in the pentouse was being restricted b/c of a backflow preventer, but we got little, if any improvement.
All of or restrooms have high flow Sloan valves on the fixtures. Sinks have those "hands free" faucets, so we don't have problems withpeople leaving them on.
If I take pressure readings at each floor and note the line sizes, would that help in deducing why we don't have decent pressure on the roof?
Dave
I'd start with looking pressure fluctuations (versus flow) in the basment where the regulators are. And adjusting the regulators to try to get them near the same setting. (less confusing info and might fix it right there).
No fix? Then maybe spot check a few fixtures on the floors and confirm that you are seeing a 4 psi (give or take) drop per floor. If so, then everything sounds normal downstream of the regulators and you need to deal with them. If not, then maybe the distribution piping is undersized or some strange component is buried in the walls.David Thomas Overlooking Cook Inlet in Kenai, Alaska
We have the exact same kind of rig here on a six story building. Two 2" and one 1" regulator, paralleled. But ours is between 4" manifolds. There are gauges built in. Static, it's about 100 + ahead of the regulators, and drifts up to 95 on the low side. When somebody runs some water, that drops to about 75, then slowly drifts back up again. Plumbing isn't what I do here, so this isn't my problem.
This paralleling seems to be not so uncommon. Perhaps price and availability of big regulators has something to do with it.
-- J.S.
This is an office building with between 500 and 600 employees. The building was originly a Sears store that we renovated to an office complex about twenty years ago. Parts of the building are operational 24/7, although the number of employees drops to around 20 or so after 7:00 or 8:00 pm, unless there is a storm. Finding a time when someone isn't using water somewhere is tough.
Waynel5, what order should I adjust the regulators? Do the 2" lines first, and then the 1", or the smallest first? I can isolate each, and maybe turn on a deep sink on each floor.
davidmeiland, the building renovation was designed by an archy firm, with attendent engineers. At the time of the renovation we had some 100+ of our own enginners. Believe me when I say nothing ever gets changed in the field on a project like this without getting approved by a commitee of them. The original prints show this parralell regulator design, but I can't find the specs for the setting pressures. The only problem we have ever had is the low pressure in the penthouse mechanical room. Washing down the 4 condenser units is a PITA. Takes 6 hours when it should take no more than 3, even if we acid wash and rinse. In my younger days a 3 or 4 beer wiz would have had more pressure than we get up there.<g>
Dave
It there a mechanical chase that you could "easily" run a new line and have it bypass the regualators?
What about gettting one of those cheap a$$ electrical pressure washers?
Nothing except the elevator shaft/vent goes from the basement to the roof.
You probably remember the Sears building on Broadway don't you? That is one of our office complexes.
Even a cheap power washer would bend the coil fins on a condenser. A normal water pressure of 65 to 70 psi works pretty good if you're carefull to attack the coil straight ahead. Get a little to far off, and you can fold the fins over. One thing I dislike worse than cleaning condenser on a BUR in 90+ degree heat is combing coil fins out.
Dave
"You probably remember the Sears building on Broadway don't you? That is one of our office complexes."
My mother said that we she and my dad were dating they would go there on dates and look at the tools.
BTW, I don't really know anything about this, but this is how I would adjust the regulators.
Pick a pressure, say 70 psi.
They pick a time when the loads are not heavy and open a valve someplace so that you care guaranteed constant flow.
I assume that they have isolation valves. Shut off all but one and set to 70. And then repeat for each of the other ones.
I don't see any advantage to staging them. But there might be something odd about there characteristics that I don't understand.
Since this seems to be "common" why not email the reguator manufacter to see if they have and suggestions.
Edited 7/29/2004 11:55 pm ET by Bill Hartmann
Thanks Bill.
You have an odd setup, so I can only guess what they might have intended.
Adjusting a pressure regulator is better done with load. In other words, turn on a few faucets or whatever when setting the regulators. They respond much better to your adjustments that way.
It's best to set each individually by shutting off the isolation valves to the others while you set one.
You'll get a pressure difference due to gravity of 4.3 psi for ever 10 feet of elevation change. So if you want 50 psi on the 4th floor, you'll need a higher pressure at the regulator on the ground floor. This pressure difference is in addition to any drop from friction in the piping. If the piping were properly sized, there should not be much drop due to friction.
I'm wondering... maybe someone's original intent was to regulate each floor separately. They got done with the first manifold and the three regulators, and the boss came along and stopped 'em short, said just run one riser to all three floors.
Yep, the best approach would probably be to have separate regulators for each floor.
With multiple paralleled regulators, all the water will flow through the one with the highest setting until resistance on that unit drops the output pressure to match the next one in the group. This is kind of a flaky setup.
I'd think it would be much better to have just a single large regulator. Though the multiple units do give you some redundancy if one unit fails "closed".
Those are probably Pressure Reduction Valves rather than regulators. The difference is that the Pressure Reduction Valves (PRVs) are designed to reduce excessive pressure and have a severely drooping pressure vs. flow rate curve while regulating valves have a flatter curve. The use of three valves in parallel was, as you have correctly surmised, designed to minimize downstream pressure variation. Ideally the valves should be of different sizes, in your situation 1-1/2", 1" and 3/4" would be ball park. The smallest should be set to open first, then the middle size and finally the largest. With three line sized valves the the P vs Vol of the first valve to open quickly drops the pressure causing the second to open and soon the third. In extreme cases this can cause hunting where the pressure will surge up and down. It sounds like in your case all are set to the same pressure and and because the flow thru each is low there is excessive pressure drop. Try staggering the settings 5-10 lbs apart, ie, first valve regulates to 65 psi, 60 psi, and 55 psi. Set them by isolating each valve at the time of maximum water demand. Turning on a number of hose bibbs may help.
The line pressure of 85 psi vs the downstream of 60 is an inadequate differential for this setup. Probably when the building was built you had higher street pressure available.
If a closely controlled delivery pressure is required a piloted pressure regulator is the best (expensive) solution.
Sorry I couldn't post my answer sooner Taunton had forgotten my password and I had to request a new one.
Thanks for the explanation and instructions. These are Watts regulators. Two 2" and one 1".
How can I tell the difference between a PRV and a regulator? I was going to get rebuilt kits for them, but the guy at our supply house could not find the number (stamped on the valve body) in his Watts book. Maybe he is looking in the wrong place since I have been calling them regulators.
Dave
Generally a reduction valve has a single diaphragm, regulators usually have a second pilot diaphragm.