View Full Version : Low Water Flow into Tub

05-11-2005, 04:04 AM
Hi All,

I've spent lots of time and money trying to resolve this on my own over the last two years so now I've come to the experts ! My problem is that the water flow into my tub is about 2.5 gpm (I actually put a five gallon bucket in the tub and timed how long it took to fill it) which takes way too long to fill up my tub (and is kind of a drag for the shower as well). I have a 3/4" main from city water and new 3/4" rolled copper service to the house (about a 50' run) off the main...I have a new PRV under the house which provides 55 psi on an outside hose bib and inside at my washing machine (I bought the gage and measured it myself)...in the shower (which may be 20 feet from where the service comes into the house) I have a new Moen single handle control valve fed by separate 1/2" hot and cold supplies off the 3/4" service.

It's a 50 year old house in a suburb of Atlanta (Decatur), but everything underneath is copper. The only galvanized piping left are three nipple pipes (if I used that correctly) that thread into the shut-offs for two toliets and one bathroom sink...I've called and paid a service call for a couple of plumbers who said that I just have to live with it...I don't mind spending whatever it might take to fix it, but I'd like to believe that what I do next will finally solve this problem. Do anyone have any suggestions or thoughts on my problem ? Thanks in adavance !


05-11-2005, 06:28 AM
Have you removed the tub spout to see if it is attached to a galvanized nipple, which may be clogged with corrosion?

05-11-2005, 07:22 AM
Thanks for the feedback Jimbo...I should have mentioned that as part of the new control valve I also installed a new nipple which connects to the tub spout. Is it just me or does 2.5 gpm for flow into the tub seem inadequate ?


05-11-2005, 03:39 PM
What does the manufacturer's spec sheet say for your valve? Many are in the 6-8 gallons/minute or more. Do you have a tankless water heater? How is the tub filler attached? Does it have a threaded connection you could put your gauge on? If so, what does it say? Have you taken the screen out and checked to see if it is clogged up? Depending on the design, it probably has screens on the inside prior to the valve. Could you have some teflon tape blocking the input? What is the pressure at the sink? How many flights up is it?

05-13-2005, 08:40 PM
Sadly I've lost the paperwork for the valve and I can't find a model number anywhere on the valve itself so I'm not sure of the rating....it wasn't a particulary expensive valve as I recall for what that's worth.

I have a 50 gallon hot water heater - about four years old - one thing that I have noticed is that I seem to have a little more flow on the cold side of the valve...as I "cross" over to the hot side (remember it's a single lever valve) the water flow does drop a little...the tub filler is attached with a new galvanized nipple from the control valve into the tub...I will try taking off the filler spout and attaching my gauge to read the psi there and post back...

Not sure what you mean by the screen ? There isn't any type of areator such as on my bathroom faucet...and I don't recall there being any inline screen when I attached the valve to the pipes..it might be possible that the teflon tape is blocking it, but even before I put in the new valve I didn't have any better flow...but I can check that out as well...

It's a one story house with a crawlspace...I'm about 60' from the street/main to the front of the house and it can't be more than 20' from where the main comes into the house to where it connects to the hot water tank...and the hot water tank is on the other side of the wall from the bathroom in a laundry room...even going down to the floor and back up it can't be more than 10-15'.

thanks for the ideas ! I'll post back with the gauge readings later this weekend.


05-14-2005, 05:15 PM
Many valves have an inlet screen to keep grit, rust, etc., out of the guts, making the valve last longer. If you have galvanized pipes, or junk from the hot water heater, or maybe sand (if on a well system), then depending on what it is, it could clog up the screen. But, you indicated that the flow before you installed the new valve was low. If so, it probably has nothing to do with the valve. Note, you can have great pressure, but if the galvanized supply is all corroded on the inside, you may have the flow of a soda straw trying to feed things. The only way to fix that is to replace the errant pipe with copper or pex. It is very common to misunderstand that pressure and volume, while related, are different things. You don't have much pressure when you flush the toilet, but the volume is huge (think of that 2-3" hole in the supply tank dumping all of that water, under maybe 5 pounds of pressure, if that). You could have hundreds of pounds of pressure and a small jet, but that wouldn't flush the toilet. My unprofessional opinion.