Shower stopped working after plumber changed the knobs.

[Squiggly0825]

Hi!

So today a plumber came and changed the shower knobs. Everything seemed right until he opened the hot knob again and barely any water comes out. The cold one works as expected. He undid everything to check if something was weird or broken, but he showed us that everything looked normal. He left saying that it might be air since we cut the water while he worked, and that we should leave the hot knob open until it starts working as usual.

The hot knob has been open for a good hour and only a tiny stream of water comes out from the shower head, sometimes stopping completely. We took out the shower head, only leaving the arm that's connected to the wall, but the results are the same.

Funny thing is that the sink that is in the same bathroom, now has extremely little power compared to the usual, and if we open both sink knobs, the shower (that's still with the hot all the way open) starts dropping a little bit more water. The change is instantly audible when we turn the sink knobs. He didn't touch the sink, or anything else besides the shower, as far as we are aware.

We checked and every other sink and shower in the house, and they all work as usual with both knobs, and only with the hot one open.

Is this normal, or should I start looking into something?
Thanks for reading, and any possible leads will be greatly appreciated.

 

[terryplumb]

What provides your hot water ?
Vented cylinder fed by a loft tank ?
Show us a pic of the shower knobs that were changed .
Are all other hot taps ,that are working ok ,on a lower floor ?

 

[Squiggly0825]

What provides your hot water ?
Vented cylinder fed by a loft tank ?

I'm not sure if this answers the question, but it's this step heater that is installed in the garden.

I think the water goes up to a big water tank that is on the roof.

These were the knobs that were changed. Apparently a piece of them broke while he was taking them out, but he went to the hardware store and showed us the new pair of these things that he installed with the knobs.

And yes, all the other showers and sinks in the house provide hot water with the same power as they always have, both in the same floor as the shower with issues, and the floor below.

 

[Alec_t]

Perhaps the old washer from the tap base is still stuck on its seat, so that only the small hole in the centre of the washer is allowing water through? Can't see from the pics whether the washers are present or not on the old taps.

 

[Mottie]

Sometimes with gravity hot water you can get an airlock if the system had been drained down. Sounds like you have an airlock in the hot feed to the bathroom. The way I’ve got rid of it a couple of times in the past if you have a mixer tap, is to hold the palm of your hand firmly over the outlet, open the hot tap and then open the cold tap. This forces mains pressure cold water back through the hot system and forces the air out. After 20 or 30 seconds, turn the cold off, remove your palm from the spout and hopefully that should clear it.