Need Advice on how to Correct Low Water Pressure

Homerepairguy

Joe,

Suggest doing more troubleshooting before doing any physical repairs.

To help you out, I did an experiment at our home. I attached a water pressure gauge to a hose bib and it read 60 psi. Had my wife flush an old toilet (not a water saver model) and the pressure dropped to 51 psi while the toilet tank was filling. Then the reading jumped back up to 60 psi when the tank stopped filling. This toilet is at the back of our home, furthest away from the incoming water line. It is fed by a 3/4" trunk line.

I had her turn on the kitchen sink cold water all the way on. The pressure reading dropped to 52 psi. The kitchen sink is at the front of our home close to the incoming water line. It is also connected to a 3/4" water line.

You can also try running the water from cold and hot faucets that are close to the incoming water line and then have someone flush the toilet. Is the water flow noticeably slowed?
- If yes, there's a restriction before that faucet.
- If no, then try all of the other faucets and see if they are affected to establish a pattern if there is any.

Note that the 60 psi pressure you measured is the "static" water pressure and does not indicate the amount of incoming water flow when faucets are opened. Also, since the hot water line to your bathroom is separate from the cold water line, the volume of the hot water flow should not be noticeably affected when you flush the toilet in the bathroom.

HRG

Joe Tilghman

Thanks for all of the help you have given me HRG

Joe Tilghman

HRG just some more input, I read your test results, while I haven't tested with the pressure guage yet while flushing water or running a faucet this morning while using the bath sink I had the hot water running and flushed the commode the volume was cut in half. this sink is about 20' away from the H/W heater also if you are filling the washer and you flush the volume is also cut in half the washer sits 3' from the H/W heater.

The H/W feed coming out of the water heater is a 1/2" line in copper transitioning to 1/2" pex going directly to the washer and then with a tee going down into the crawl space. I thought all feeds coming out of the water heater were supposed to be 3/4"?? and then transition to 1/2""

Homerepairguy

I duplicated your test. I turned on the hot water in our bath sink to max and then flushed the toilet next to it. There was no change at all in the flow of hot water in the sink.

I don't know about different pipe sizes for water lines going into or out of water heaters. Someone else will have to chime in on that. I just know that all of the water heaters that I've worked on for us, family and friends have all had 3/4" in and 3/4" out.

But regardless of whether the hot water line is 3/4" or 1/2" out of your water heater, the flow of hot water from your bath sink should not be affected by flushing the toilet. As you know, the hot water line is completely separate from the cold water line that's feeding the toilet. I wonder if your toilet is incorrectly connected to the hot water line?

Try this: Turn the hot water on in the bath sink next to the toilet until you can feel hot water flowing out. Remove the cover from the toilet tank and flush the toilet. Is the water filling the tank cold or hot? If it's hot, then your toilet is connected to the wrong water line.

If you find that the toilet is connected to the cold water line, and since your hot water flow in the bath sink and to your washer are cut in half when you flush the toilet, then it seems that the problem is somewhere in the incoming water line before your water heater.

Trace the water line coming in from the city, to your pressure regulator, from the pressure regulator to the manifold that feeds cold water to the house and to the water heater. Let us know how they are connected and what size pipes they are.

HRG

Joe Tilghman

HRG,

I was one step ahead of you checking to see if the toilet tank water was hot, it was cold indeed I won't be able to get under the house until Sat. to check whats going on with the water inlet.

Will let you know. Thanks again

jaydevries

is it only the shower that is having low pressure issue or are sinks affected by it also

__________________
be careful my advice only comes from general knowledge i know about the 4 rules it takes to plumb and they are
1 poop needs to flow down hill. 2 hot on left cold on right
3 i get a pay check on Mondays 4 do not chew finger nails at or after work.

Homerepairguy

Just to verify, hot water needs to be coming out of the bathroom sink faucet before the toilet is flushed for the test to be valid.

Homerepairguy

Joe said (3 posts prior to yours) that the flow of hot water in his bathroom sink is cut in half when the toilet is flushed.

jaydevries

thanks sorry i missed it

__________________
be careful my advice only comes from general knowledge i know about the 4 rules it takes to plumb and they are
1 poop needs to flow down hill. 2 hot on left cold on right
3 i get a pay check on Mondays 4 do not chew finger nails at or after work.

Joe Tilghman

HRG,

Confirmed, the hot water in the sink was running before I flushed.

And to remind the washer is also affected when I flush and it is 2 ft from the water heater.

Homerepairguy

Looking back at your posts, there is some conflicting information.
..... a. In your original post, you said that 3/4" pipe was coming out of the water heater and it transitioned to 1/2" PEX about 10 feet out.
..... b. In another post you said that 1/2" pipe was coming out of your water heater.
..... I'm assuming now that in item-b you really meant item-a. Is that right?

To summarize what I understand so far:

1. All of your home, hot and cold, was re-piped in 1/2" PEX.

2. There is a 3/4" pipe coming out of the water heater which transitions to 1/2" PEX ten feet away from the water heater.

3. When you flush the toilet in the bathroom, the hot water from the bathtub faucet goes to a trickle. (Or is it only from the shower head that goes to a trickle?)

4. When you flush the toilet, the volume of hot water from the adjacent bathroom sink faucet is cut in half.

5. When you flush the toilet, the volume of hot water to the washer is cut in half.

QUESTIONS:
1. Are all of your input cold water lines up to the water heater input 3/4" pipe?

2. Do you have any galvanized pipes in your system?

3. Is the cold water system also plumbed in 1/2" PEX?

If you can post a diagram of your plumbing configuration which shows what size pipes are where, "galvanized, copper or PEX" where, that would be helpful.

HRG

Joe Tilghman

HRG to answer your questions.

!. the entire house is plumbed in 1/2" pex trunk and tee.

2. If you flush toilet all fixtures tub faucet and shower head and washer loose haalf of volume.

3. Cold feed to water heater is 3/4" pex. I assume it tee's off in 1/2" pex in crwl space before passing through floor. After it passes through floor it tee's off to 1/2" pex to feed cold side of washer then continues to cold feed to water heater.

4. Hot feed out of water heater is 1/2" copper transitioning to 1/2" pex feeding hot side of water heater then teeing off back into the crawl space to feed hot water to fixtutres etc.

Hope this answers your questions

Homerepairguy

With 3/4" pipe from the city to the input of your water heater, no way should the volume of water out from the hot water faucets be cut in half when you flush the toilet. Unless there is a blockage somewhere.

Is the pipe from the city or any other pipe galvanized? (I suspect the old pipes in the house are galvanized since the house was re-piped using PEX.) Maybe there's blockage in a galvanized pipe?

Try a water flow test. Get a 5 gallon bucket. Since most 5 gallon buckets hold 5 gallons when the water level is an inch or two from the top, use a measured container to calibrate the bucket to 5 gallons and put a mark inside the bucket. Or you could just wing it and assume 5 gallons is 1.5 inches below the top.

Put the 5 gallon bucket directly under a hose bib (no water hose) and time how long it takes in seconds to fill 5 gallons with the faucet fully open. Then check the flow rate of the hot water faucet in your bathtub and/or laundry tray. If the 5 gallon bucket won't fit, use a bucket that will fit and time it in seconds. Post the results.

BTW, the flow rate in gallons per minute = (nbr of gallons/number of seconds to fill) * 60. I read that the max flow rate for 1/2" pipe is about 6 gallons per minute in a typical house.

HRG

Joe Tilghman

HRG,

as far as I can tell there is no galvanized being used in any pluming, all of the galvanized I found has been un done now I assume because the may have been a blockage I don't know when the pex was plumbed in.

I will do the 5 gallon test from a bib closest to where the city water enters the house and the tub to night. and let you know.

But I still plan to get to the part of the house where the city water enters and connects to the house. It is a little tight back there.

Joe Tilghman

HRG

I did the test you described. I had to use a measured test 1 gal. I could not get the 5 gallon bucket under the hose bib.

Test 1. from the hose bib it took 40 seconds to fill 1 gal.

Test 2. from the tub it 50 seconds to fill 1 gal. I did both hot and cold from the tub times were identical.

If my math was right it would have take 3.3 minutes to fill 5 gallons at the hose bib. And 4.2 minutes in the tub for the same volume