Low Water Pressure after Check Valve Replacement: Quick Boiler Temperature Drop & Air Release

Hello.
I had a failure of the check valve, so I replaced it with a new one and after this replacement a problem arose.
The pressure of the hot water coming from the boiler has dropped very much, the water is flowing in a very small stream and I wonder what could be the cause of this?
Apart from that, although the water flows very slowly, the temperature in the boiler drops very quickly - for 3-4 minutes of washing and it drops from 100 to 50, which was not the case before.

When I changed the valve, first I turned off the water supply to the apartment, then I drained all the water from the boiler with the tap - I suspect that I could somehow air the system - especially since after turning on the shower, when hot water flies, there are such moments that it lets out air.

Tell me, am I on the right track?
If not, what could it have happened?
And how to fix it ?

greetings
Sandal

pictorial diagram

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Hi.
You write, Buddy, that "then I drained all the water from the boiler with the tap". As far as I know, hot water is taken from the top of the boiler.
For hot water to run, cold water must flow in, i.e. cold water pushes warm water out. Therefore, it is impossible to drain all the water through the tap. Unless some artist edited it.
The non-return valve is mounted on the inlet of cold water to the boiler, and its task is to prevent backflow of hot water to the cold water system. These valves are actuated in the correct direction. One way the water flows normally and the other way it does not flow or if the valve is bad it flows very slowly Perhaps you turned the valve on the other way and that is your problem.

mietek.r wrote:

pictorial diagram

Added after 5 [minutes]:

diagram again

The safety valve is installed right in front of the boiler, of course, on the inlet.

Added after 3 [minutes]:

Zbyszek-G wrote:

Hi.
Perhaps you turned the valve on the other way, and that's your problem.

It cannot be the other way around, because after 1 - the valve has a water flow arrow, after 2 there is an external thread on one side, and an internal thread on the other, and there is no other option than correct connection.

I look at the diagram and you have to be a prophet to guess what's going on.

My guess is that this is a vertical electric boiler! only poco on the side on top of the safety valve.

Question. If you changed the valve then:
1.No hemp gasket popped for installation.
2. Ball or disc shut-off valve fully open or only closed.
3. old or new installation? The safety valve is something like a strainer to protect against contamination and can be killed especially when turning off the water and draining it causes the limescale to break off.
4. That the boiler is well vented.

Added after 3 [minutes]:

I look at the diagram and you have to be a prophet to guess what's going on.

My guess is that this is a vertical electric boiler! only poco on the side on top of the safety valve.

Question. If you changed the valve then:
1.No hemp gasket popped for installation.
2. Ball or disc shut-off valve fully open or only closed.
3. old or new installation? The safety valve is something like a strainer to protect against contamination and can be killed especially when turning off the water and draining it causes the limescale to break off.
4. That the boiler is well vented.

The non-return valve is mounted on the supply, the blue color on the diagram shows an arrow in the direction of water flow - the red color means drainage and the valve, as the name suggests, is safety and must be safe in the event of overheating of the water, in such a boiler you can heat the water like in a boiler locomotive if the heater thermostat is blocked.

Added after 4 [minutes]:

Check the non-return valve if it is not clogged there is no philosophy here - connect without a valve, you will make sure whether the valve or the installation is in place and draw conclusions

After such work, also clean the strainers in all spouts.

Every year for the winter, I drain the water from the installation in the catering establishment, disconnect the electric boilers and blow the installation with a compressor. I plug everything back in in the spring.
Most often, when the water flowed poorly, the cause was a clogged airflow strainer in the faucet spout.
In the case of the old boiler there may be a problem with the calcified hot water pipe (along the entire length inside the boiler)
Once I had a case of a defect of a hose - factory blocked inlet - a drawpiece (boilers are connected on flexible hoses), check / safety valves (two-function) most often damaged so that they simply liquid or let the water from the boiler return back and when someone drew cold water on the floor below he had a free hot water and my boiler was cooling down strangely fast.
Air in the boiler can be a problem when you turn on the boiler without first filling it with water - in the best case the limescale will fall off the heater, it will settle on the bottom of the boiler, in the worst case you will burn the heater.
If you just turned on the hot water before connecting to the power supply and waited for the water to flow without air, then there is no problem.
If you accidentally changed the hoses on the boiler connection and connected the other way round, the symptoms may be similar to those described by you - the boiler would only fill up partially and the heated water flows at low intensity through the leaky non-return valve.
Therefore, I propose to check the correct connection of the boiler to the installation once again. If everything is OK. Check it after unscrewing the hot water hose and giving cold water to the boiler whether the water flows from the boiler intensively or weakly, if it is OK. these are clogged screens in the batteries.

Hello recently I was removing the boiler from the wall after re-hanging the connection, the pressure of hot water in the tap dropped
. Someone will tell you what's the fault?

[quote = "sandal"] Hello.
I had a failure of the check valve, so I replaced it with a new one.
What was the check valve failure?

Replaced hoses and everything.