Odd flow rate

[Richard Moore]

1935 3br 1½ba house with all interior plumbing newer copper but galvanized street feed. The house sits well back from the street (150+') and probably 25' above. 70 PSI static pressure.

So...when I first turn on the bathroom sink, flush the toilet and turn on the tub faucet the flow rate was good. Cool, I think...briefly. But then, over the next 30 seconds or so it slowly reduced down to maybe a quarter of the initial flow. Hmmmm. I wait for the toilet to finish filling and try just the sink and tub. Again, the flow rate was good, but then slowly reduced at both fixtures. Odd. I turn them off and back on again immediately. Same poor flow. BUT...if I wait a minute or so, the flow starts off good again. Here's the even stranger thing...After the flow reduced and I turned off both fixtures, then, if I first turn on the tub shortly after, the flow is still poor there. If I then turn on the sink the flow at the sink AND the tub suddenly jumps back to good...and then slowly dies again.

The copper plumbing looked to be professional and well sized and there was nothing unusual about the risers (all visible in the basement). Nothing else out of the ordinary (no well pump, storage tank, etc). There was a normal sized thermal expansion tank at the water heater. I've seen lots of poor flow due to clogged old pipes, but it's always immediate. I've never seen flow rate slowly diminish like this (or jump back temporarily to good).

I suspect it is somehow related to the galvanized feed and my recommendation is for plumber evaluation and repair and/or upgrade. I'm not given to "guessing" in the report. But, if anyone has any idea what the hell is going on here, it might help de-addle my noggin. [:-spin]

[Nolan Kienitz]

Richard,

It has got to be the squirrels in the treadmill that is running the pump to pull the water "up-hill". They must be getting tired. []

Now that I've thrown in the "I don't know ... smart-a$$ comment" ... I'll just come out and say: "I dunno."

I had a low flow in the Master Bath Suite the other day, but not variable like yours.

[David Meiland]

Are we talking cold water only, hot water only, cold/hot together...?

[Jim Katen]

My best guess is that you missed booster pump somewhere.

- Jim Katen, Oregon

[John Kogel]

My best guess is that you missed booster pump somewhere.

- Jim Katen, Oregon

Yep, it is acting like a pump with a water-logged pressure tank, so the pump is cycling.

I found a pump in a crawlspace a few mos ago, house has always been on town water. The only explanation was a booster pump to compensate for low pressure in the supply line.

[Richard Moore]

Are we talking cold water only, hot water only, cold/hot together...?

Both, either, together.

My best guess is that you missed booster pump somewhere.

If I did, it's not inside the home. From where the street feed entered the basement, all of the home's plumbing was easily visible and basic. Nothing labeled at the panel either. There was an inaccessible area of a crawl (another matter) but it was under a corner of the house, well away from any likely plumbing.

I also checked an older report from a nearby home. 75 psi there so it seems unlikely a booster pumper would be needed. They're very rare around here.

[tbird]

Is there a water pressure or expansion tank on the system or water heater? That would hold enough to provide a fast flow until it was near empty, then trickle down to the flow rate of the main.

[inspector57]

I get that same type effect when the water valve at the meter is only partially on. See if this fits. The system is pressurized when you arrive and you turn on the water to see good flow which slowly dwindles as the outflow exceeds the inflow. Turn it off for a while and pressure rebuilds. Leave it on and the flow eventually matches the inflow and remains constant.

This would act just like a waterlogged pressure tank except you are using the static pressure in the lines and hot water tank as your pressure vessel. You may even have some air in the Water heater or some water hammer arrestors or dead end pipes somewhere in the system.

Any restriction in the main line be it a valve or pipe would have the same effect.

Just my opinion.

[Richard Moore]

As I mentioned, there was a TX tank at the water heater, and also a pair of hammer arrestors at the laundry. Air in the water heater itself doesn't compute as it was a top take-off. I think everyone is on the right track but, unless there is a hidden pump or large pressure vessel as some suggested, the amount of water that runs before it slowed down seems like way too much for the combo of TX tank and arrestors.

It was almost amusing at the inspection. At one point I had the the client and realtor in the bathroom as I repeatedly demonstrated the good-flow-good-flow-aaannnnddd-now-see-how-it-slows routine. We all agreed it was really weird.

One thought that just struck me. The home only had a half bath for the two bedrooms at the upper level. Maybe they installed some extra lines at the same time as the newer copper for future expansion and it's those capped off lines that are providing the extra air reservoir? Yeah...that's the ticket! I can live with that.

As for my clients, I'll leave it up to the plumber to determine what is actually happening and confirm the likelyhood that they need a new street feed.

[plummen]

is there a regulator somewhere in supply line?

[barlyhop]

Last time I ran into this, it turned out to be a damaged line from the street. Customer side of the curb stop, they paid to repair it, about $1500 or so.

Only noticed the poor pressure on the second floor of the house in this case.

[esch]

Sounds like the water line running from meter to house could be alot smaller then the water lines inside the house causing the larger lines in the house to be working similar to a tank. At first alls well then they bleed off their pressure faster then the service line refills them.

Matt