Help advice sought on strange water pressure problem

[Oiseau]

I am refurbishing our bathroom and because I have moved bath tap position requiring more pipe I flushed the pipes without taps connected. I immediately noticed that the cold water was emerging at a lower pressure than the hot. The bathroom is 15 meters away from the cold water inlet and both immersion heated pressurized hot and the cold travel side by side, in same size pipe, without sharp bends to the bathroom. Any ideas on why or more importantly how to improve the cold pressure would be welcome.

Thanks in advance.

Oiseau

 

[JCplumb]

Welcome to the Forum Oiseau.
You really need to give us more to go on.
Pipe sizes/materials, types of joints used, are there flexis involved ( just for Sys ) where does the bathroom cold feed come from etc.
At present it's like asking an auto mechanic to tell you why your car won't start with the only clue to the state of your car being 'it's red'

 

[dancinplumba]

Welcome to the Forum Oiseau.
You really need to give us more to go on.
Pipe sizes/materials, types of joints used, are there flexis involved ( just for Sys ) where does the bathroom cold feed come from etc.
At present it's like asking an auto mechanic to tell you why your car won't start with the only clue to the state of your car being 'it's red'

pmsl, love it jc

 

[mountainman]

'Need more to go on' seems to have fallen on deaf ears!

 

[Howsie]

He's probably in the bath. I'm sure he'll be along shortly.

 

[Oiseau]

Welcome to the Forum Oiseau.
You really need to give us more to go on.
Pipe sizes/materials, types of joints used, are there flexis involved ( just for Sys ) where does the bathroom cold feed come from etc.
At present it's like asking an auto mechanic to tell you why your car won't start with the only clue to the state of your car being 'it's red'

Sorry.... been out.

So, pipes are 16mm (I'm in France !)
No flexis
Bath cold feed comes from close to hot water tank.
Both hot and cold are identical in size, direction, no other take offs etc

When flushing out together the pressures are noticeably different, and when you close the hot water supply at the tank and just leave the cold running, there is NO increase in pressure.

What I find strange is that normally, I think !!, it's the hot that might have a slight drop in pressure in comparison to the cold, I cannot understand why this is different.

I realise bath supplies should be 22, but over here they seem to always do them in 16 but I think they have a higher pressure, and we are close to the water tower which is very high !

Thanks to all replies, especially the humorous ones, it's good to be around a bit of building site humour !

Oiseau

 

[Billy Bob Bob]

you need a combi:clap:

 

[mountainman]

Sounds like there is a restriction somewhere, but only someone on site can be more positive.
Btw, being in France doesn't necessarily make you a bad person.

 

[JCplumb]

So after you turn the hot off there is no instant increase in cold pressure?
Sounds like your cold feed is teed off the supply to your immersion header tank, so turning the hot tap off means that the cold supply is still replacing the used water from the hot supply.
If you don't use the taps for a while then turn the cold on by itself - does it run with better pressure?

 

[Oiseau]

So after you turn the hot off there is no instant increase in cold pressure?
Sounds like your cold feed is teed off the supply to your immersion header tank, so turning the hot tap off means that the cold supply is still replacing the used water from the hot supply.
If you don't use the taps for a while then turn the cold on by itself - does it run with better pressure?

In France we don't have header tanks, it's all pressurised,

I have tried various combinations of turning hot and cold off and on and still no increase in pressure on the cold. My conclusions are also that there is a restriction in the cold feed to the bathroom.

Are there any tricks of the trade to solving possible pipe restrictions, I have thought of compressors and pressure washers, or maybe it's just as quick to run a new feed in although it's in the attic and underneath a mountain of 'stuff'.

 

[Oiseau]

......
Btw, being in France doesn't necessarily make you a bad person.

Thanks for the reassurance, although a lot of Brits would disagree with you !

 

[snowhead]

Is there a Pressure regulating valve inn the mains cold feed to the hot cylinder with the bath cold feed coming out of it as well?

P.S I went to France once, but it was full of foreigners, so I came home again.

 

[Oiseau]

Is there a Pressure regulating valve inn the mains cold feed to the hot cylinder with the bath cold feed coming out of it as well?

There is, I think !, a pressure regulating valve on the cold feed near where it comes into the house. The cold then 'T's' off to the bathroom before continuing on to the immersion hot tank and kitchen sink

P.S I went to France once, but it was full of foreigners, so I came home again.

Yes I noticed that at first, then after a while I couldn't tell the difference, so I stayed because the croissants are better than the crumpets !