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JLeslie's avatar

Is the water flow different between a bathtub and kitchen faucet?

Asked by JLeslie (55945points) April 10th, 2015 from iPhone

I tried googling, but became frustrated. I know there are numbers on water flow, but none of the information I am finding answers this specific question. My assumption is a bath faucet carries more gallons per whatever when wide open compared to a kitchen sink, but I don’t know.

If they are different, are the pipe sizes also different?

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16 Answers

Judi's avatar

The pipe size should all be the same. Usually ½ inch or ¾ inch
I don’t think the tub faucet would carry more gallons per minute but I’ll ask Jeff in the morning to be sure.

LuckyGuy's avatar

The pipe sizes are identical, unless the plumber needed to do something different for the final hookup. To save water some new faucets have aerator/restrictors installed at the outlet New York State was giving restrictors away free last year as part of a water conservation effort.

LuckyGuy's avatar

I know a while back there was a push in Florida to conserve fresh water. Maybe there is a specification for new home construction, like low flow toilets.

JLeslie's avatar

It doesn’t have to do with the home I built.

Florida does have restrictions, but things like shower heads you can remove sine part and the water flows more. My shower in my master is really good, maybe my builder already removed it. I don’t know if they restrict other faucets? I never even thought there might be restrictions on bath or kitchen faucets. I lived in FL when there was a huge change in those laws and at the same time it was when I first became aware you can buy six head shower systems. It seemed like a colossal joke.

elbanditoroso's avatar

The difference I have seen is in the faucet itself. As you note, some shower heads have those little plastic restrictors, which are easy to remove.

Some kitchen faucets have small air inputs on the side which introduce small amounts of air which aerates the output -which sort of widens the stream and gives the impression of better pressure.

If you are having pressure issues, it could either be the long pipe distance from the home input to the bathroom, or that the faucet screen (which is usually the last little screwed-on device in a faucet) is utterly filled with grit and grime, and needs to be cleaned out.

Adirondackwannabe's avatar

All of my sink faucets have those screens that @elbanditoroso mentioned. They cut the water flow by about half. You can unscrew them if you want to see the difference. The tub faucet does not have a screen. The water comes out unrestricted.

bossob's avatar


The UPC (Universal Plumbing Code, used in the USA) specifies maximum fixture flows in gpm (gallons per minute). States and municipalities can add requirements to the UPC. Currently, I think that tub faucets and outside hose faucets are the only unrestricted fixtures in residential applications.

I don’t have time at the moment to find more references, but here’s a sample flow rate requirement chart specified in Los Angeles.

For contrast, unrestricted tub faucets and exterior faucets will be 5+ gpm depending on supply line size and condition.

Judi's avatar

WE put body sprays in our shower and still had issues. We are on a well so we had the pump experts come out and had plenty of pressure coming out of the pump. The problem was that the guy we bought the house from went cheap and put ½ inch instead of ¾ inch and no matter how much pressure we gave to the shower heads couldn’t get enough water for all those body sprays. We now keep one set off until hubby get’s ambitious enough to re plum the line from the pump to the master bedroom.

LuckyGuy's avatar

@bossob That is a great chart. I am so jealous of the pressures they mention. We are at 50psi. Do people really have 80psi in their houses? Do they use it to wash the roof?

JLeslie's avatar

To be clear, regarding my very specific question I am curious about a kitchen faucet vs. a bathroom tub. I was not asking about showers in my original question that came up separately. I don’t mind the tangent at all. I am interested in all of it including the pipe information

Part of my curiousity is if a kitchen faucet could be used for a tub and the water would be filling the tub as quickly. I have a sprayer on my tub, but it’s separate from the faucet, and much more expensive than a kitchen faucet that can be all in one.

@bossob Thanks!

bossob's avatar

@LuckyGuy I hear ya! My well is regulated 40/60 on/off. Some municipal supplies require a pressure limiter/regulator for each meter because the trunk pressures are so high. The regulators are typically around 80–85 psi.

@JLeslie The insides of tub faucets where the water flows through, are larger than the insides of kitchen faucets. Even without the restrictors that others have mentioned, a kitchen faucet will have a lower rate of flow than a tub faucet.

JLeslie's avatar

I learned a lot on this Q. Thanks everyone.

LuckyGuy's avatar

This might be applicable. I have Moen faucets in my bathroom sinks and showers. Installed around 1990. One of the bathroom sinks and one shower had slow drips. I put a cup under them and measured about 8 to 16 oz per day. Not bad enough to fix but enough to keep the sink and floor wet.
I bought a cartridge and puller tool and replaced the sink cartridge in about 30 minutes It works beautifully!. So I decided to tackle the shower. I did not know the model so I had to take it apart first. While doing so I had some issues. I could not shut off the water and did not want to force it so I called Moen Consumer Service.
The guy answered and before I I could get anywhere he started asking me my zip code, my name my address. Just I was about hang up on him he said “What’s your situation?” I told him and asked my question. He was so helpful. He then asked for an email address so he could send instructions. I gave it to him. Then he said “The replacement cartridge has been shipped. You will receive it in 3 days.” What? “Our faucets come with a lifetime warranty on the cartridge. There is no charge.” Wow!
When I checked my email there were the instructions (very clear) and two shipping confirmations. The second shipping confirm was for a screw I had clumsily dropped inside the wall. I had asked him to tell me the length and he just sent a new stainless steel screw, already treated with loctite. Wow!
The shower fix also took about 30 minutes and works great!

JLeslie's avatar

Great PR for Moen! I wonder if Kohler, and all those well known brands, do the same? Very interesting.

LuckyGuy's avatar

You can either interpret it as good PR for Moen or bad PR that their faucets leak after 25 years of use. (The other 3 faucets do not leak by the way.) I was truly surprised by their immediate and efficient response. I had no idea about the warranty – no paperwork necessary.

In my life I’ve only had one other company respond the same way: Ruger firearms. I had something old that belonged to my father and didn’t work. I called to get a part so I could fix it myself. They asked for my address – which I was reluctant to give out. I just wanted the damn part. They guy said something like “Look, all our parts have a lifetime warranty. We will fix it for free. Just tell mey your address, or someplace else, so I can send you the prepaid shipper.” I did – and they did. Fantastic.

Judi's avatar

Jeff says the aerator in the kitchen faucet will slow down the flow a bit. Otherwise, there are usually no other flow restrictors in a kitchen faucet.

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