H & C water balance

[huw169]

Hi all
This is an excellent forum that I have gained many good tips from. That said, I can't seem to find anything relating to my particular problem - probably not looking hard enough!

Anyway, I would appreciate some advice on this problem please.
I have a boiler specifically for hot water situated in the kitchen of my flat. There is no header tank as it is connected directly to the main water feed. Open the taps and it fires up no problem with excellent heat and good pressure. It is a Chaffateaux (Sp?) Corvec Brittoney IIa.
It is also connected to my bathroom which is about 7m from the boiler and the shower head which is directly connected to the baths mixer tap set.
I have always had to turn the hot on fully in the shower and then crack the cold about half a turn to get a good temperature. This was fine until a few weeks ago.
Now I open the hot water tap fully and get a good temperature (I can't put my hand under it), but when I crack the cold open it reduces the pressure going through the boiler and shuts down the heat.

I have de-scaled the pipework from the boiler to the shower head, and the heat exchanger in the boiler. The boiler diaphram was replaced about 2 months ago. The problem is that it is intermittent. Some times in the evening I have a great shower with loads of control, but other times in the evening, and mostly (if not all) in the mornings it is crap.

I also have one of those AquaMag things on the cold feed into the boiler. (My mother bought it, but never had it fitted - honest) this has been on for about 3 months as I live in a hard water area - Portsmouth.

Any suggestions would be greatly received.
Many thanks
Huw

 

[Slugbabydotcom]

First thing to check

Is your mains stoptap fully open?

 

[huw169]

Yeah - that has been checked and tried.
Cheers

 

[fitz1]

Intermitant low pressure in ur flat. Tell ur neighbours to stop running the water when ur having a shower.Its a case of demand times.(sounds like that anyway)

 

[Slugbabydotcom]

There is usually a small isolation valve under the multipoint water heater make sure that is fully open also. Its usually a screwdriver slot affair. [In line with the pipe = on. Across the line of the pipe = off]

What's your water pressure like in general? Is there a poor flow from cold taps? If so it may be worth asking your water provider for advice.They should send an insepctor out to you.
It may be that you are just in a low pressure area. There could be a nearby burst water main or maybe a restriction anywhere in your service pipe and through to your boiler

 

[huw169]

fitz1 - We have our own supplies into each flat so I doubt it is anything local. It aslo only started happening recently - sometimes when the other flat is empty.

slugbaby - I am going to call my water provider, but I wanted to try and cover all the angles first so they don't just shrug me off. The cold water pressure does still seem fine.
They have built a new estate just down the road and I'm wondering if they are supplied from the same pipe - may just be on the edge of being acceptable. I don't have a little 90 degree isolator valve under my boiler, but I do have a little tap which is fully wound out.

Has anyone put a pressure meter on their water mains? I could then see how much it fluctuates. Any recomendations? I have seen a 100m dial guage for £30 designed for pressurized systems up to 10bar.

Had an excellent shower tonight, but who knows what the morning will bring.

Cheers
Huw

 

[Slugbabydotcom]

You stated in your last post that

the cold pressure seems fine

. This points to a restriction between the cold teeing off the rising main, through the water heater and up to & including the hot outlet.

Rather than assume its fine it is possible to measure if its fine.

Instead of thinking about pressure I find it better to concentrate on flow rates as they reflect the end product better [hot water]. Static pressure can build up past a restriction so you may have excellent pressure but if your flow rate isnt there you have problems
Checking flow rates at various points say a hot tap near your shower, a cold tap near your shower and through the shower itself should point you to where the restriction is. Unless it states differently in the instructions I would say that you need 10.5 ltires per min thats 1.75 litres in ten seconds. I'll let you do the maths from there depending on what containers you have to measure with.

but I do have a little tap which is fully wound out.

Just above this tap is or should be a filter / washer.Just in case you havent already> Make sure this is cleaned out as debris from when they were working down the road could have blocked it.

After that theres a few things that could be going wrong in your water heater but you start getting into corgi territory.There is a manual here http://www.chaffoteaux.co.uk/britony_iit01.htm for the II.t which should be near enough the same, but I'm sure if you need the precise info that they will send it if you email them.There is a section there on low pressure at the bottom of page 10 and a few other bits of info if you read through it.