A different water pressure problem

[Paulus]

Hi Guys

I went to look at a job tonight, full bathroom refurb. There is an existing electric shower but, as they have a Valliant combi boiler, I suggested that they do away with it and have a thermostatic shower valve as the combi will supply sufficient pressure.

Water pressure at the hot taps is good, water at the cold taps is good. When I turned on the hot tap and then the cold, the hot water reduced to little more than a trickle. Mains water pressure is around 3 bar.

I have never come across this before, has anyone got any ideas as to what may be wrong please?

 

[Mike Jackson]

poor flow rate into the property. Could be a valve not fully open, minor blockage somewhere. undersized pipes etc. We get it a lot around here with old galvanized mains that have furred up over a period. I've had flow rates as low as 3 l/min from the cold main.

 

[Paulus]

I didn't have time to measure the flow rate but it does seem to be excellent at the bath taps and washbasin taps when hot and cold taps are turned on independantly.

 

[dancinplumba]

lots of this round here thats what they get from incoming main and low pressure

 

[Simon F]

is it just at the one hot tap or at all of them?

 

[diamondgas]

Hi Guys

I went to look at a job tonight, full bathroom refurb. There is an existing electric shower but, as they have a Valliant combi boiler, I suggested that they do away with it and have a thermostatic shower valve as the combi will supply sufficient pressure.

Water pressure at the hot taps is good, water at the cold taps is good. When I turned on the hot tap and then the cold, the hot water reduced to little more than a trickle. Mains water pressure is around 3 bar.

I have never come across this before, has anyone got any ideas as to what may be wrong please?

There's a big difference between standing pressure and working pressure Paulus! I'm guessing you checked standing? Standing really just checks what you can have without any restrictions. Working pressure & flow rate, as mike says, is much more important in finding out IMHO!

 

[Paulus]

is it just at the one hot tap or at all of them?

It is at all of them Simon.

 

[Paulus]

There's a big difference between standing pressure and working pressure Paulus! I'm guessing you checked standing? Standing really just checks what you can have without any restrictions. Working pressure & flow rate, as mike says, is much more important in finding out IMHO!

It was working pressure I checked at garden tap with cold water tap in kitchen on.

 

[dancinplumba]

if enuff presure to operate elec shr you will have enuff to operate shr valve, but its what flow rate will be
imo

 

[diamondgas]

It was working pressure I checked at garden tap with cold water tap in kitchen on.

Interesting Then cold working is okay but hot is compromised I'd be thinking ... Boiler issues that may be a blocked up filter, flow restrictor or plate hex? take your pick even supply pipe out to hot taps Paulus ... I'd be wanting to check the hot water flow pressure and rate on max next I think !!

 

[Paulus]

I'm not gas safe and don't touch boilers but the customers have a service contract. I think I'll recommend that they have the service company check it out and earn some of this money that is paid to them every month.

 

[diamondgas]

I'm not gas safe and don't touch boilers but the customers have a service contract. I think I'll recommend that they have the service company check it out and earn some of this money that is paid to them every month.

Just a thought! Make sure someone hasn't turned down the iso on the boiler inlet! If the pressures that good then maybe someone restricted the flow through the boiler just to pacify the custard and get them hot water???

 

[dancinplumba]

soz iv'e been on the wrong track, thinking pressure drop to both hot and cold

 

[Mike Jackson]

So was I.

 

[diamondgas]

soz iv'e been on the wrong track, thinking pressure drop to both hot and cold

I wouldn't rule it out IMO DP... However, as no doubt you know, it ends up a process of elimination and finding any kind of blockage is time consuming

 

[Paulus]

The pressure drop is only to the hot water and only when I run the cold water at the same time. With the cold off, the hot water pressure is excellent. I'm thinking boiler problem or restricted flowthrough boiler as diamondgas says.