Can I determine high/low pressure myself?

[QuackingPlums]

Hi,

Forgive me if this is answered elsewhere, but I couldn't find anything appropriate using the search.

I want to replace my taps in my en-suite with Hansgrohe Allegra Talis S units, which are available in either high or low pressure. I want to buy these before calling in a plumber to fit everything, but I don't know how to tell what my water pressure is. I have a new-build (<3 years) 3-storey property, and the hot water cylinder (HS MegaFlo) is on the middle floor. The boiler is downstairs, and there's no tank in the roof. I have a gauge on the cylinder which reads 1.5bar, but I suspect this is static pressure. There are pumps to feed the hot water around the house - the shower on the floor above the cyclinder is a reasonable pressure but not "painful", if that makes any sense. I can't see anything on the pumps that would indicate the operating pressure.

Any advice?

Thanks in advance!

Eric.

 

[seco services]

megaflo is a unvented mains pressure system.

so high pressure.

 

[QuackingPlums]

Wow, that was quick! Brilliant, thanks! Once again DIYnot has proven invaluable!

 

[JohnD]

How to tell:

no tank in the roof

If you have no cold-water tank, then the taps must be fed from the mains.

Mains is high pressure, tank is low pressure.

Seco got it a different way

 

[QuackingPlums]

If you have no cold-water tank, then the taps must be fed from the mains.

Mains is high pressure, tank is low pressure.

Thanks John.

I kinda worked myself that the cold taps must be fed from the mains pressure, but I got a bit confused when thinking about how the hot water got its pressure. I can't imagine how the hot water can "inherit" the mains pressure since it just sits inside the hot water cyclinder, yet it must be pumped up to the floor above somehow!

I'm sure it's all obvious to plumbers!

 

[doitall]

I think you should clarify the pump part of your post as you cannot pump the hot water from a megaflow

 

[QuackingPlums]

Ok, maybe I'm using the wrong word. There is a red pump in my airing cupboard, a few inches above floor level, next to the Megaflo.

Coming out and upward from that is a fat pipe that feeds about 3 of those little silver timer valve boxes (I assume this is what these are - they're wired into a blanking plate on the inside wall of the cupboard). There are two fat pipes coming out of the bottom of the cylinder though, and somehow are part of this arrangement of pipes/pump/timer boxes.

I think the hot water taps (and showers) are fed from the top of the Megaflow, so the pump probably has nothing to do with that. Central heating only maybe?

 

[seco services]

thats just the pump on the common feeds to pump the water round your rads/hw coil from the boiler.
not to pump the dhw that relies on mains pressure.

 

[Goldberg]

megaflo is a unvented mains pressure system.

It doesn't have to be.

How to tell:

no tank in the roof

That isn't how to to tell, because there could be a cold storage cistern that isn't in the roof.

 

[QuackingPlums]

That isn't how to to tell, because there could be a cold storage cistern that isn't in the roof.

So what would one of those look like? I have this red thing in my airing cupboard above the Megaflo (ignore the comments - this pic is from another of my posts):

Untitled

• QuackingPlums
• 7 Dec 2008
• 2

Is that a cold water storage tank? It's very small, and I have to open the little black valves every few months or so to charge the pressure back up to 1.5bar.

 

[petit_pablo]

The red tank is the pressure vessel for the CH system ignore GB

 

[Goldberg]

I have this red thing in my airing cupboard above the Megaflo

Is that a cold water storage tank? It's very small...

No. It's an expansion vessel for the primary circuit.

...and I have to open the little black valves every few months or so to charge the pressure back up to 1.5bar.

Oh dear - you probably have leak somewhere. Also, the repeated addition of fresh water carries a risk of the radiators corroding, which would lead to circulation problems.

 

[doitall]

That isn't how to to tell, because there could be a cold storage cistern that isn't in the roof.

So what would one of those look like? I have this red thing in my airing cupboard above the Megaflo (ignore the comments - this pic is from another of my posts):

Untitled

• QuackingPlums
• 7 Dec 2008
• 2

Is that a cold water storage tank? It's very small, and I have to open the little black valves every few months or so to charge the pressure back up to 1.5bar.

The red vessel is for the boiler and primary side. e.g. heating.

It does suggest a small leak on the heating.

It looks a really good, neat job, going on the pic.

 

[seco services]

megaflo is a unvented mains pressure system.

It doesn't have to be.

so what would you supply it from ?