Low pressure on the hot water in the shower cabin only?

[Xakepa]

First, sorry for the English but my Dutch is still very primitive.

I have a 20-year old house with Nefit HR Ecoline CV-ketle + 120l boiler combination on the attic; single bathroom on the 1st floor (bath + shower cabin + 2 sinks). Previous owner never provided a map of the piping but I'm working that out. So I see 4-way hot water manifold at the exhaust the boiler, with identical 1/2" OD pipes. The inlet valve to the boiler fully open, seems OK. I can't measure the inlet pressure at the boiler but hot water pressure in the house is ... not impressive. Could be the incoming cold water, could be the pipes are plugged, could be the boiler, I might have a hot water leak etc etc etc

The problem is the hot water pressure in the shower cabin is VERY low (the cold water pressure in OKish), while on the other 3 faucets it seems OK - or at least it's definitely higher.

I know for a fact there are no valves b/w the boiler outlet and the shower cabin rough-in valve. So I cut the tile to get to to the rough-in valve and that one is some old Grohe monster with what seems like 52mm (2"?) nut that I can't remove (see pic) - I ordered a box spanner from Amazon... of course the isolation/needle valves on both sides were open OK (I played with those too for no avail)

Anyway, my questions are the following
1)What is the chance I'll find the rough-in valve plugged/worn/smth. It seems probable as the other faucets in the bathroom seem ... better. But I'm worried.

2)As the hot water pressure in house is substantially lower than the cold water - how probable is that the old boiler is plugged, and is there a way to flush the hot water system without. I know boiler is super old and have to go but that's 2.5-3K euro that we're not very happy to dedicate

3)Last one - if I upgrade directly the whole thing (i.e. for example Nefit Trendline 30kW CW5 + 120l boiler) can I combine CW5 ketle with CW6 boiler?

Thanks a ton. Quite stuck here ... with the family showering in the bathtub

 

[CV__]

1/2" piping is not likely. More likely 12mm. Drop the imperial units; they are a pest

What Nefit boiler do you have and from what year? At some point they made a whole series where the riser tubes degraded and broke down inside the boiler. One symptom is that you can only use a small amount of hot water before it turns half-warm, since the cold inlet is then at the same height as the hot outlet (because the tube broke down). Perhaps in your boiler fragments of the hot witer pipe broke down in a way it blocks the exits.

You do mean the passive hot water storage tank as "boiler", right?

1) Honestly no idea. Did you check if the shower has the flow reductor installed?

2) See above. See cost comment below

3) Most people in NL don't have a separate boiler. A boiler in combination with a gaspowered central heating is just as storage tank that allows you to shower with multiple people at once or to allow heating the house at the same time. What we call "combiketel" can heat water for heating your home and for hot tap water.
Some Nefit heaters from that time, I think the 28 kW one in that line, had a huge tap limit (would not start unless you opened up the shower to max...). That is another reason for a separate boiler next to it (but that boiler is just buffer / storage).
So most likely you don't need a separate boiler either. That's saves you that expense.

If you do want a separate boiler; buy a heatpump boiler. There is a €1250 subsidy for that.

To come back to your original question number 3; yes; you can combine CW5 ketel with CW6 boiler. The boiler is just passive storage. The limit is always in the kettle.

>> There might be some language confusion.
In Dutch we use the word "boiler" for the hot water tank, either heated with electricity or as a passive buffer. For the device that actually burns the gas, we use "CV ketel". If that CV ketel can heat tap water AND heat the home, we also call it a "combiketel". There is also an obscure segment of separate gas-burning boilers, but those are super rare.

 

[Xakepa]

Again, sorry for the language mess. And THANKS!

I have Nefit EcomLine HR30 CV-ketel, serial 268-97-02-5158, attached to 120l (yes, a dummy) "boiler"/buffer/reservoir Nefit "CV-boiler" serial 722-97-21-0041. That makes it 1997, 22 years ... we bargained 2K off the house price because of the old CV ... now comes payback time.

- No, the warm water runs consistently hot (fills the bath tube w/o dropping in the temp). The boiler does not seem broken.
- I took both the shower head and the hand shower head of course. The pressure when fully hot - actually the flow - is just as good to provide about 2-3cm fountain height at the hand shower.
- I fully unscrewed the needle/blocking screw at the rough-in valve from the hot side. I can block the flow with my finger ...yeah, it burns a bit. That's about 2 atm or less IMHO. Definitely low.
- Once I get the 52mm box spanner from Amazon I will find out whats behind the wal :) Lets hope the valve is the culprit.
- I'm getting the same feedback from my colleagues: you don't need a separate tank/boiler nowadays. I have to research that further - these dummy boilers are so expensive!

Feel fr** to recommend a solution - the house is fully detached, 3 floors, 640m3, in-floor heating on the ground floor, 1 bathroom, family of 4, nothing fancy but I want full blast hot shower and I'm not saving on that.

 

[stefffan]

More probable is that rust, calcium, debris, and sediment is simply upsetting the flow of water. The issue could be essential in the showerhead or tap itself, particularly on the off chance that you've seen that one outlet has great pressure while another is low. if not hot water pressure is weak in all of your home's appliances, it's most likely due to sediment build-up in your water heater. no matter how best showerheads you own you should Clean your shower head often.