Hot water low pressure problem

[AldeanFan]

I’ve noticed recently that the hot water pressure at my kitchen sink is much lower than the cold water pressure.

When I turn on the hot water and the water is cold at first there is the same level of flow as when I turn on the cold water, but as the water warms up the flow and pressure visibly decreases.

I don’t have this issue with any other sink or faucet in the house.

I’ve also noticed the dishwasher doesn’t clean as well as it used to.

where do I start to try and solve this problem?

 

[Bucko]

We have a similar issue with our kitchen sink. It was going cold halfway thru the dishes and then would come back. We are relatively new to the home and my current theory is when the well pump kicks in the cold side has increased pressure due to less paths of resistance so it holds the hot back a little at the mixing valve.

As for the dishwasher I run the kitchen faucet until the water is hot so the dishwasher does not fill with cold water and have to wait for the element to warm it up. You may have a bad heater element in the dishwasher.

 

[Valveman]

Low water pressure in general can be caused by the well or booster pump cycling on and off. With a 40/60 pressure switch, by the time the "well pump kicks in" at 40 PSI you have lost a full 1/3rd of your pressure. After the pump kicks in it quickly fills the tank to 60 PSI and shuts off. The larger the pressure tank you have the longer the pressure is on the low side. This on at 40 and off at 60 can make the pressure seem weak, especially when compared tp having strong constant 50 PSI all the time.

When the system pressure is on the low side, the hot water pressure is really low due to the added restrictions of the water heater. I am sure you have a restriction in the hot water line somewhere. Sometimes the water heater makes calcium build up which can clog lines and fittings as well as the water heater itself.

I also find that a lot of restriction is from Pex pipe. The insert fittings in 3/4 Pex make it only 1/2" dimeter on the inside. 1/2" Pex has insert fittings that makes it work like 1/4" pipe, which causes a lot of restriction in pressure. If the pipe is too small or has restrictions, increasing the constant pressure setting of the Cycle Stop Valve from 50 to 60 or even 70 will push more water through small pipe. Of course that also means increasing the setting of the pressure switch to 50/70 or 60/80 respectively.

I always hate it when someone complains about pressure from their well or booster pump system. It is your pump system. You can have as much pressure as you want. You just have to make it happen. With strong constant pressure from a Cycle Stop Valve you won't even need soap in the shower. Lol! People with "city like" pressure will be envious of the pressure in your shower.

 

[dcg9381]

Are the other faucets the same volume? I wouldn't expect a bathroom faucet to flow as much as a kitchen faucet necessarily.
If you open several bathroom faucets set to hot, do you get a volume reduction?
Dishwashers often have strainers in-line with the water line, so I might check there.
Is this a tanked water heater? Do you have a well or on city water?

 

[Wrench97]

Is the dishwasher if fact hooked to the hot water?
If so the problem is before the sink faucet is there a shut off valve before both the dishwasher and the faucet, I would start there.

 

[BillK]

I wonder if something is swelling up from the heat and slowing the flow once the hot water gets to it ?

Maybe a washer in a shut off valve ? Make sure the valve is open all the way.
Maybe something in the faucet itself ?

 

[AldeanFan]

Thanks,
We’re on city water so it’s not a well pump issue.

it could be the flex hose to the sink faucet swelling when it gets hot, I think I’ve got a spare line so I could easily replace that and eliminate it.

the dishwasher was new last year and is next to the sink, it may or may not be related to the sink faucet issue, or it might jus be a not very good dishwasher

none of the other faucets do this, the upstairs bath has so much water pressure it will splash out of the sink.

 

[Milton Shaw]

Check the dishwasher valve for a screen. They tend to catch crud from the hot water heater. You probably have to remove the valve and the water inlet fitting to clean the screen. Same thing on the water faucet and check the faucet nozzle. While you are at it if you find anything check the washing machine for the same problem.

 

[Ohio Auto]

Put a new faucet on first ... we just had the same problem. There was some type of element/filter inside the hot side of faucet that was partially clogged. Cheapest diagnostic try ... if it's not your problem you're not out much.

 

[Valveman]

Thanks,
We’re on city water so it’s not a well pump issue.

Then you may need a booster pump. Many cities have inadequate water pressure and/or there are houses at higher elevations or out at the far ends of the line that do not have good pressure. Adding a booster or jet pump controlled with a CSV can deliver really strong constant pressure in these applications just like from a well pump.

 

[AldeanFan]

Check the dishwasher valve for a screen. They tend to catch crud from the hot water heater. You probably have to remove the valve and the water inlet fitting to clean the screen. Same thing on the water faucet and check the faucet nozzle. While you are at it if you find anything check the washing machine for the same problem.

Thanks I’ll try this, easy stuff first

 

[AldeanFan]

Put a new faucet on first ... we just had the same problem. There was some type of element/filter inside the hot side of faucet that was partially clogged. Cheapest diagnostic try ... if it's not your problem you're not out much.

Sounds like a good plan, thanks

 

[AldeanFan]

Then you may need a booster pump. Many cities have inadequate water pressure and/or there are houses at higher elevations or out at the far ends of the line that do not have good pressure. Adding a booster or jet pump controlled with a CSV can deliver really strong constant pressure in these applications just like from a well pump.

I don’t think that’s the issue, we have very good water pressure, definitely stronger than my parents in the next town over. It’s only the kitchen sink where I find there is a problem and the dishwasher may not be a flow problem it could be totally unrelated

 

[CraigStu]

I realize that my experience isn't the same, didn't have any relation to temp, but I fixed our bathroom faucets several months ago. The end of the faucet has a screw-on cap that has a bunch of plastic washer/screen pieces inside. There were 6 layers all together. I removed three of them and flow/pressure nearly doubled. You have to experiment which ones to remove since some of them will eliminate the aeration function and then the water splashes too much.

 

[Wrench97]

Depending on the type of faucet I've seen sink sprayer diverter valves act up under hot temps.

 

[The Cobbler]

almost for sure it's something swelling with heat . just need to identify what it is. I don't think the same issue is causing your dishwasher problem,I would hazard a guess you have 2 issues
I know years back Moen had inline restrictors that were total PIA. we used to remove them with a woodscrew into them & pull them out with a pair of pliers

 

[AldeanFan]

So I’m still dealing with this problem.
I’ve checked all the faucets in the house and only the dishwasher and kitchen sink have low water pressure and only on the hot side.
It’s as if there is a restriction on the hot water line to the kitchen.

Last night I disconnected the feed line to the dishwasher and put it in a bucket and it’s getting very little pressure and very little flow.
Then I took the kitchen faucet apart, and found no restrictions in the faucet which supports my theory that it is a flow problem to the kitchen.

Not sure where to go next, there is quite a bit of pipe between the water heater and the kitchen. I’m seriously considering closing all off all the hot water shutoffs and the water heater feed and opening just one hot then putting compressed air to the dishwasher feed to see if I can blow it out.

 

[aandpdan]

What kind of piping is used? Pex, copper, galvanized?

 

[dcg9381]

Not sure where to go next, there is quite a bit of pipe between the water heater and the kitchen. I’m seriously considering closing all off all the hot water shutoffs and the water heater feed and opening just one hot then putting compressed air to the dishwasher feed to see if I can blow it out.

That's what I'd do. Disconnect the hot feed at the water heater and blow the lines out with compressed air.

 

[CraigStu]

Just be careful w/ air pressure. Most house water systems are in the 40-60# range. Most air compressors are in the 125-150# range. Also you want to run the air pressure in the opposite direction from normal water flow. I'd disconnect at the water heater and at the dishwasher. I'd put the air in at the dishwasher.

 

[Wrench97]

Is there another shut off valve for just the kitchen?

 

[The Cobbler]

what about right at the connection for the dishwasher and faucet . that's kinda where I would start looking first .

 

[AldeanFan]

I may have found the problem,
I went down in the basement and traced the pipes with a flashlight.
Up in a hidden corner I found a shutoff valve with no handle. It is on the hot feed to the kitchen. It could be restricting flow to my kitchen.
The hot line runs under the sink and t’s off to the dishwasher feed so if this shutoff is the problem it accounts for both my dishwasher and sink problems.

Hopefully tomorrow I can find time to take the valve apart and see if it’s clogged.
And hopefully I can reassemble it without any leaks, otherwise I’ll cut it out.

 

[Bucko]

I may have found the problem,
I went down in the basement and traced the pipes with a flashlight.
Up in a hidden corner I found a shutoff valve with no handle. It is on the hot feed to the kitchen. It could be restricting flow to my kitchen.
The hot line runs under the sink and t’s off to the dishwasher feed so if this shutoff is the problem it accounts for both my dishwasher and sink problems.

Hopefully tomorrow I can find time to take the valve apart and see if it’s clogged.
And hopefully I can reassemble it without any leaks, otherwise I’ll cut it out.

Alot of the 1/4 turn valves are plastic inside and get stuck with crud. When they are forced it can distort the plastic and partially block the line. If the valves don't freely turn on and off it may be the issue.

 

[The Cobbler]

since the flow reduces as the water heats up, I would first suspect rubber washers that are loose, distorted or not fully open. second a washer that has broken away from it seat , or another piece of debris stuck inline somewhere

 

[AldeanFan]

Well I’m crossing my fingers that the problem is fixed.
I took the mystery shutoff valve apart, it’s seized so I can’t tell if it was partially closed, but it was pretty scaly.
I cleaned it up and removed the washer for better flow and put it back together.
Now the hot water at the kitchen sink flows the same as the cold!

 

[CraigStu]

Excellent news.

Alot of the 1/4 turn valves are plastic inside and get stuck with crud. When they are forced it can distort the plastic and partially block the line. If the valves don't freely turn on and off it may be the issue.

I hate the 1/4 turn valves. There were a lot of them in our previous house and all were super stiff to operate. And a lot of them were installed somewhere in the middle of a 10ft piece of PVC so virtually no support. Our current house is just 3 years old and doesn't have many of the 1/4 turn valves fortunately. I always install the old school style gate valves.

 

[The Cobbler]

great news