We live on the second floor in an older apartment building (1928). I don’t know when the plumbing that’s here now was put in.
I have a weird on-going issue with the shower. It is the kind with two taps, one for hot and one for cold. When you are in the shower, if you decide the water is too hot and would like it cooler, you can do one of two things (this isn’t the weird part)…
A. Turn the hot water tap down
or
B. Turn the cold water tap up
The weird thing is that in my shower, when you do either A or B, the water gets hotter, A LOT hotter, before it eventually runs cooler. I would say maybe 45 seconds to get cooler, maybe longer – it’s hard to keep track when you’re being scalded. It’s enough of an issue that we have to warn house guests about it before they shower. It’s especially a problem with the B method – turning the cold tap up makes it extremely hot before it runs cold.
I’m kind of thinking you’ve got a valve problem – well, two valve problems.
WAG from a non-plumber: when you turn the cold water up, you’re turning a screw that should move the washer farther away from the valve seat, but the washer is staying behind somehow, and flopping into the flow, blocking the cold water until it flops back into place.
I can’t guess exactly what’s wrong with the hot water valve, but I’ll bet neither of those valves has been maintained for too long, and some consequence of severe wear is responsible.
It’s fairly normal for the perceived temperature to increase temporarily when you turn up the cold tap on a mixer.
What you’re effectively doing is increasing the flow rate through the shower, as soon as you turn the cold tap up. However, initially that just pushes the hot water that is already in the pipe (between the tap and the shower head) out faster. Result? More heat per second - the temperature itself hasn’t changed, but the amount of hot water per second has, which will make it feel hotter.
If there’s a long pipe between the tap and the shower head, that can last for a few seconds, but not as long as you are reporting, so this is probably not the cause.
If you have especially a showerhead on a hose, like some places, the lag between changing temperature and feeling the result can be several seconds. Worse if you have a new water-saving showerhead.
In old bathtubs, there’s 4 feet plus between the tub taps and the showerhead. Even in a shower stall, it could be 3 feet or more. Add a five foot hose attached where the showerhead could be, and that’s about 10 feet of pipe.
The other possibility is pressure issues; in an apartment, maybe your hot water tank is in the basement and the hot water is pumped circulated all through the building. There’s a slight energy loss but you don’t have to wait 5 minutes for the hot water to reach you from the basement tank. (In my bungalow, it can take 30 seconds for the hot water to reach the master bathroom). Maybe this pump is producing a slightly higher pressure than the city feed cold water. You turn on the cold, the hot runs into the cold pipe as well as out your showerhead. Then somehow the pressure adjusts, all that hot in the cold pipe comes back, then the cold arrives.
Except in that case, the shower pressure would drop meantime… unless there’s also a cold water pressure pump somewhere that has to kick into give you pressure beyond the first floor… I don’t know how apartments are plumbed…
Hmmm, no. There isn’t an access space, at least not like in places I’ve lived in before, where you could open a hatch in the wall.
It’s an old tub, with the taps and faucets mounted on the wall in the center of the long side of the tub (as opposed to on one end, like with most modern tubs). There is no access there, if you went in, you’d be breaking through the tile/plaster. There is access to the drain at the end of the tub.
This whole thing is making me intrigued to learn more about how apartments are plumbed.
The taps are on the wall in the center of the long side of the tub, the showerhead is about 3 1/2 feet above them, the tub spout is below. Between the taps is the … I don’t even know what it’s called, it’s the same hardware as the taps, and you turn it to switch from tub to shower.
The center handle is called the diverter. What you have inside your wall looks something like this. The hot and cold water enter through the fittings below the hot and cold water cartridges, and they meet in the center. The brass cartridges in your shower valve look something like this. As you turn the handles, the plunger on the bottom of the cartridge moves back and forward to control the amount of water that’s let through from the supply pipes. That rubber washer on the end forms a tight seal against the seat on the inside of the shower valve to prevent leaks when the faucet is turned off.
By default, the water goes out the bottom down to the tub spout, unless you turn the diverter to close it off, in which case it exits through the top and goes up through a pipe to the shower head. If the burst of hot water were of a short duration, I would agree with Colophon, but I’m mystified by what would cause that to last for 45 seconds or more.
When you turn on the hot water, does it come hot right away or within a few seconds (hot water circulated by pump) or does it take 20 or 30 seconds, as you expect if it has to come from your hot water tank, 50 or 100 feet away? (Where is the tank?)
I have the same kind of fixture as you, with 3 knobs, and a hose fed shower head. I do notice the effect Colophon mentioned, increasing the cold makes the water feel hotter for a little while. However, it never gets to scalding, and changes back in about 5 seconds.
I would suggest you test the system a bit. When you lower the hot tap, does the flow rate immediately decrease? When you raise the cold tap, does the flow rate immediately increase?
Also, does the system drip at all? Hot or cold water? When you divert the water to the shower head, do you get any flow out of the tub filler, or does it divert completely?
The hot water does take about 30 seconds or so to get hot; the hot water tank is in the basement and we live on the second floor.
Other than this hot/cold issue, the plumbing is good - we don’t have any drips when the water is turned off, when the shower is selected nothing drips from the tub spout.
This thread has been really helpful in that:
I now know a lot of plumbing vocabulary
I’m actually going to ask for a plumber to come check it out. I was wondering if I would get any replies like “yeah, that’s a thing that happens with older/outdated plumbing and here’s why” but it seems like there’s agreement that there’s a problem.
