Two days ago I got a £700 water bill - ouch!

I confirmed that I had a "leak" and traced it to a 3 bar safety valve on the cold feed to the mains pressure boiler. The problem is that the water pressure coming into the house is between 4.5 bar and 5.5 bar and the valve is opening.

So today I've…

Fitted a 1-4 bar adjustable presure reducer
Replaced the 3 bar safety valve (just in case)
and added a second pressure gauge after the reducer.

But I still have a problem..

The first time I turned the water back on the pressure to the boiler was about 3.5 bar and the safety valve was partly open as before.  So I tried to get the pressure reducer to do it’s job. I turned it down to the minimum but I can only get the pressure down to about 3 bar with the taps off.

The spec for the reducer says 1-4 bar adjustable so what gives?

Set like this as soon as I turn on a tap on the pressure falls to 0.5 bar and I get very little flow. It seems like the pressure reducer is really a flow rate reducer as it has little impact on the pressure with the taps off.

Have I got a duff pressure reducer or do they all work like this?

[quote author=thescruff  link=1122128999/0#1 date=1122133113]What you could do with is a corgi engineer. instead of trying to save you money it's costing and you still have a problem.
[/quote]

Thanks for the reply.  Sorry for the lack of info (see below).

I agree with the above  - except there aren't many Corgi engineers this side of the channel  
 
The Boiler is a Junkers/Bosch Condensing Gas boiler supplying Central heating rads and a mains pressure  hot water cylinder. I think the model number is ZWR 24. The label the installer peeled off and fitted says ZR 24 but the installation manual (in Dutch) says the ZR 24 model is heating only and the ZWR 24 is heating and hot water.

Quote:


Sorry I wasn't clear - it's definitly not the heating circuit filler. The filler has two stopcocks on it (both off) and  the pressure in the heating circuit has been stable at 2.5 bar for a year or more.

The problem is the cold supply that gets heated to produce hot water.  Now that I've translated the installation manual I'm reasonably sure that the max water pressures are:

Heating circuit 2.5 bar
Cold water input 12 bar. (Max. Sanitaire waterdruk)

The plumber who installed the system three years ago didn't seem very bright. He managed to give himself an electric shock by drilling through mains cables burried in the floor. After he had recovered I watched him prepare to drill another hole - I stopped him while I went to buy him a cable finder. He didn't do the gas or the electrics himself - perhaps just as well.

Yes.  

I think what happened is this...  When the heating was installed the mains water pressure was probably 2 or 2.5 bar and the installer fitted a 3 bar relief valve to protect the whole system.  Then sometime in the last year the water company increased the pressure to around 5 bar and the relief valve opened.

Without knowing it we've been loosing water through that valve.  

As I said I've tried installing a pressure reducer in the line to the system (before the relief valve) but it doesn't seem very effective.  I'm beginning to wonder if it's faulty.  

Ideally what we need is a presure reducer that reduces it to 2.5 bar with the taps off without drropping it to 0.5 bar with the taps on.

No I'm not messing with an unvented sys. Not that daft

Let me try a different tack...

Lets assume my washing machine and dishwasher are also rated for 3 bar max but the mains is coming into the house is at 5 bar. The 3 bar safety valve installed to protect everything is therefore open and gushing water.

I know it would be daft to change the safety relief valve for one with a higher rating because then it wouldn't protect the WM or DW. (It would be like fitting a too big a fuse in an electrical circuit).

So I installed a 1-4 bar pressure reducer/regulator to try an bring the pressure down but doesn't seem to work. With no water flowing through it the pressure is still too high. With water flowing the pressure and flow rate is too low. Perhaps it's faulty?

Are there different types of pressure reducer/regulator?

Thanks thescruff...

The water supply comes into house, goes through the meter and a stopcock. Then in the meter cupboard there is a pressure gauge marked 0 - 10 bar. It reads between 4.5 and 5 bar and I've seen it moving so I know it's not stuck.

Then there is a short length of pipe about 1ft long  acting as a manifold. Several smaller pipes lead off from this manifold - most are 15mm. For example one goes to the kitchen sink, another to the garden tap, another to the loo. eg a "Star" layout.

One of these pipes goes to the heating system about 15 meters away. The boiler is wall mounted with the H/W tank underneath. The layout makes it quite easy to see this is the cold feed to both the H/W tank and the filler for the sealed heating system. As far as I can tell it doesn't go anywhere else.  The heating and hot water system is performing normally.

Roughly half way between the manifold and the heating system in this cold supply there is a pressure relief valve marked 3 bar. The valve was found to be open which I assumed was because the input appears to be at 4.5 - 5 bar. The outlet from the valve goes into a 32mm plastic waste pipe via a "funnel".

The relief valve has now been replaced with the folowing in series...

A 1-4 bar adjustable pressure regulator
A new 3 bar relief valve
A pressure guage marked 0-6 bar

The intention was to adjust the regulator to drop the pressure back down from 4.5 bar to under 3 bar, but even with it at minimium the guage reads around 3 bar and the valve is "on the edge" and dripping. That's much better than it was though.

With the regulator set like this opening a hot tap causes the pressure to drop to 0.5 bar and the flow is poor. We didn't have a problem with poor flow before I installed the regulator (eg with the pressure limited to 3 bar by the open relief valve).

Other feeds from the mainfold in the cupboard go to other appliances such a dishwashers and washing machines. I have't yet located a pressure relief valve in the feeds for them but they seem to have survived operating on 5 bar for perhaps a year.

Not sure what more I can add.

Don't forget that CWatters is not effected by UK regulations as he is in Belgium, if the heating side of the boiler would be filled with a filling loop and then shut off at the minimum pressure required, if you are talking about the cold feed to the unvented cylinder you mentioned a maximum pressure for the cylinder of 12 bar, why not change the PRV for a 6bar one

from your posts you mention that the boiler is rated at up to 12 bar on the hot water side.

given that the guage on the meter is only rated to 10 bar it would seem unlikely that the water supplier will exceed this so could you not remove the valve altogether? or is this necessary to comply with local regulations?

just to confirm, this device that has been causing the problems appears to be on the water supply and not directly a part of the heating system and it also apears that the boiler is rated for an incomming supply presure far greater than your water main is likely to deliver.

otherwise, is the water meter also a pressure reducer? the inclusion of a guage may mean that there is a degree of adjustment there so you may be able to reduce the overall pressure here without affecting the flow rate??? might be worth a look.

ok just re read the bit about the tank underneath???

but you say its not a sealed system? i'm confused ???

this hot water tank is fed directly at mains(all be it regulated) pressure, is that not a sealed setup then?

hmm going over my head now

ah well just a though or rambling

hope you have luck with finding the right bit

Here is a shetch of how I think our system works. The problem was with the relief valve at the bottom. The dotted line with two stopcocks is the primary filler.

Note the guages read: 5 bar on the mains in. 3 bar after the pressure regulator and 2.5 bar on the primary.

Now that I have installed the pressure regulator the relief valve is no longer tripping (just). However when you open a hot tap or shower the pressure after the regulator falls to about 1 bar and the flow rate isn't anything like as good as before. I'm 90% sure this is due to poor quality regulator. I've tried two different makes from DIY sources and will try a physically bigger device when I get chance.

That's the problem. I have the manual for the boiler but not the cylinder. It's made by Junkers but it's one of these "white boxed" units that looks like a fridge. It's all rivited together and full of foam so I can't see inside. Just the four pipes coming out plus a temperature sensor wire. There might be an expansion unit in side but I'd never know.

The only writing on it refers to replacing a magnesium anode every two years.