mixer shower problems

[bones75cbr]

Hi all,

Just moved into a new house and having trouble with hot water in the shower.

*there is PLENTY of hot water getting to the mixer as the connection pipe is RED hot to touch
*at normal operating height i just get luke warm water most of the time though on occasion it as been hot??
*if i take off the rail and drop down i get hot water!

The info!!!

The shower is a Tapmate Riva mixer shower.
The boiler is a potterton netaheat.
The shower cold runs from the tank and the hot is from a the top of the cylinder in the loft.
The run is about 5m in length from cylinder to shower.
the cold water tank is around 2ft highr than the cylinder.


Any ideas on what i need to do to resolve?

Thanks again,

 

[Softus]

Any ideas on what i need to do to resolve?

If it's a new house then just call the builder or installer and get them to fix it.

If not new, then when did it last work?

 

[bones75cbr]

No its not a new build. Its been like this since we moved in, but only now getting chance to have a look at it. Its war but not hot and theres plent of really hot water left in the taps etc.


Thanks.

 

[mogget]

Its war

Let battle begin

What size are the pipes between tank / cylinder and shower?

Do these pipes feed anything else?

Is the pipe from the cylinder coming from the very top connection on the cylinder, or does it have its own tapping?

 

[bones75cbr]

The hot water feed comes from the very top of the cylinder in 22mm. This reduces further down in a Tee to 15mm the other part of the Tee continues in 22mm and is feeding hot water to the bathroom (i think?)

Thanks,

 

[mogget]

OK,

With the shower head in its high position, what is the vertical distance between the shower head and the bottom of the cold water cistern?

What size is the cold feed pipe to the shower?

Is this a manual mixer shower or thermostatic?

 

[Softus]

Its been like this since we moved in

Really?! 25 years ago?!

 

[bones75cbr]

Its been like this since we moved in

Really?! 25 years ago?!

 

[bones75cbr]

From bottom of cold water tank to shower head 1500mm (give or take 100mm)
Cold water feed is 15mm
Manual mixer.


Thanks,

 

[mogget]

I think what is happening is this, no doubt I'll be shot down in flames if I'm wrong!

When there is no flow, the pressure of the hot and cold supplies is equal as they are both supplied from the same tank.

The cold water flows through a relatively direct pipe to the shower.

For the hot, water flows round a few bends into the cylinder, pushing hot water out the top of the cylinder, round a few more bends, down to a tee and around another bend into the shower. So the resistance of this path is higher.

When the shower is operating this creates a difference of pressure between the cold and hot supplies, causing your lukewarm water problem.

When you lower the shower head, the working head of water is more, and the difference of pressure is relatively less so you get warmer water.


The ideal way of sorting this out would be to have dedicated hot and cold supplies for the shower valve, but this is the real world

I would suggest first checking the shower hose, cheaper ones often have a smaller bore (7mm or so) and will add to the problem. A proper full-bore hose might be enough to solve the problem.

Other than that, in practice changing the valve for a thermostatic one would probably sort things out for you.

 

[Tipper]

Are you in a hard water area? Mixer could be scaled up.

 

[bones75cbr]

Cheers for all the advice,
Thanks,