Water pressure drops drastically when using hot water for bathtubs?

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Grimnebulin

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My family purchased a new home a few years ago. This issue has always been present, but I'm finally getting around to figuring out the issue.

Our water heater is in our basement and our bathtubs are on the second floor (2 floors up). If we try to fill the tubs with hot water quickly, the water pressure drops to the point where it takes 30 minutes or more to fill the tub. However, we do not lose hot water. It just takes a long time. This does not happen if we let the hot water fill slowly, nor does it happen with any other plumbing fixtures in the house. It's almost as if the previous owners put some type of regulator in to limit how much hot water can be used at a given time.

However, I admittedly know nothing about plumbing, so I don't even know if this is possible. The problem is very frustrating, so any ideas are greatly appreciated.

I will also mention that we lose a decent amount of water pressure when we flush toilets as well. I don't know if this has to do with our water heater tank, but we haven't replaced that since we've been in the house, and I wouldn't think that would be in play with flushing toilets.

Thanks!
 
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You say you bought a new house.
Is this newly built, or an older house that is just new to you?

Are you saying that the tubs actually fill faster when the hot water valves are partially choked back?

And when fully open, the hot water flow is weaker?

If so, there is possibly a problem with the nipples that adapt the water heater to the house plumbing.

Some nipples have little valves inside that are meant to limit heat escaping upwards into the house plumbing, while water is not being used.
Heat trap nipples.
These can malfunction, and can restrict full water flow.

You can remove the old nipples, and replace with regular galvanized nipples, or galvanized nipples with a plastic coating on the inside called dielectric nipples.

Post some pics of the plumbing on top of the water heater.

Please give more info about house plumbing, copper or galvanized or pex?
Age of house.
Are these giant bathtubs?
Do you have a whole house water filter?
A water softener?
Is there a pressure reducing valve where the water service enters the house?
Are you on your own well water?
 
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PS please create some paragraph breaks, it makes long posts easier to read and follow.
 
Thanks for the quick reply! I'll do my best to answer. Here you go:

The house is just new to us.
The tubs do appear to fill faster when partially choked back, but I've never done a time study to check that against opening it wide and letting the issue occur.
The plumbing is all copper from what I can see.
House was built in '98.
One bathtub is a large hot tub style and one is not. The problem happens when filling either.
We don't have a whole house water filter.
We do have a water softener.
I'm not aware of a pressure reducing valve on the house, but I wouldn't know one if I saw one.
We are not on well water.

Thanks again for the help
 
Do a timed tub filling test to verify the problem that you first posted about.

If tubs fill faster when hot water flow is restricted, it could be that the nipples are heat trap style and should be removed.

Or the tub faucets have anti scald, pressure balancing function, and somehow running full open is causing them to choke back the hot water.

Sounds like you could change the cartridge and pressure balance module in one faucet, for a test.

Or change out the water heater nipples, even if they are not heat traps, they often get corroded and narrowed inside, mostly on the hot side.

Probably time to have a plumber or more qualified friend or relative start looking at all these possibilities.
 
Post a clear pic of the labels on your water heater.
Brand name and model.

Maybe we can figure out if it came supplied with heat trap nipples?
Or maybe it is 21 years old, and nipples are corroded and restricted inside?
 
876628D2-6E4F-4252-9517-B0735C3D7309.png Your heater does have heat traps, see pic.
#2 and # 5 are little valves stuck into the nipples.
 
I am only saying you have heat traps, which MIGHT be the problem.

Can you post a pic of the plumbing on top of the heater?

You might be able to disconnect the plumbing and pry these heat traps out.

That might fix the issue, it might not.

It might also be a problem with the tub faucet valves.

Or just weak water pressure in the house, sometimes hard to push high flow rate of water up two stories.

The showers and other house fixtures have much slower flow rates than bathtubs.

You might need to have the inlet filter on the softener cleaned out, or clean out the resin bed with Iron Out or similar cleaners.
 
I would try removing the heat traps and leave them out.

Usually you can get something thin like a knife edge under the lip, to tease them out.
 
The serial number has encoded info on manufacturing date.

I got that off the Bradford White website.

Then they allow three extra months for expected shipping time and time spent in warehouses etc, or any typical time between manufacture and being bought and installed.

Most water heaters, furnaces, major appliances etc, have a date hidden in their serial number.
 
When talking about the pressure loss and/or flow rate reduction while filling the two tubs, are you typically using 100% Hot water?

Do you check the LAV cold water flow changes and or pressure reduction while tub(s) are being filled?

How often to you typically replace you water softener media?
 
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