Age old hot water pressure problem...

[wimper]

Please don't shout at me!! I have done quite a bit of research, but am coming up a little short somewhere! So I'll start at the beginning (it seems a good place to start!)....

I bought my house almost 1 year ago exactly, it's my first house. It's a 1990's Bloor Home. One of the first jobs I had to do was sort a shower out. The previous owner had never had a shower on the wall!

So keeping it cheap (I'm going to refit the bathroom soon), I bought a Plumbsure mixer, with showerhead attachment, from B&Q - See here;

http://www.diy.com/diy/jsp/bq/nav.j...mpid=4&tmad=c&ecamp=cse_go&CAWELAID=563954617

Upon installing, I had issues with the hot water pressure. The shower has hot water fed from the gravity hot water system, and the cold from the mains. I have confirmed this as there are only two tanks in the loft - one small overflow for the CH, and one large for the hot water cylinder). Basically the issue was that you can turn the hot water on full, and then just tweak the cold on and the shower runs cold.

Due to the initial poor performance, and after speaking to a couple of plumbing folk, I figured that the issue was unequal pressures. To help solve this, I fitted a isolating valve to the cold water pipe before the tap, and tweaked it until I could mix the shower properly.

The problem with this is that when my girlfriend wants a bath, I have to reopen the isolating valve to get enough cold water. A right PITA as I am sure you can imagine.

So, here is what I have tried/checked;

All valves open
Ball cock floating properly and tank water at a good level
Checked for obstructions in the exit pipe from the header tank
Taps are suitable for low pressure and not 1/4 turn jobies
Tried filling the loft tank more

The reason I'm asking now is because the boiler is on it's last legs. This means I have the age old decision of replacing like for like, or going for a combi. I think a combi would probably help with the flow mismatch, but as the house is a 3 bed detached, so suited for a small family, I believe that stored hot water would be a better option.

This would mean that I still need to improve the shower somehow. I know I can pump it, but I just wanted to check opinions on here first. Am I missing something?

A few system specs;

Boiler: Glow-worm Economy Plus 50F
Water tank height above the shower head: 600mm (give or take 20mm)
Shower head height above the tap outlet: 1450mm

A few pics;

Tap entry to the bath

Hot water cylinder (obviously)

Loft tank - the water sits about 1 inch up the overflow pipe.

Today I have recorded the following flowrates;

From the tap;
Hotwater: 9.1 l/min
Cold restricted: 1.8 l/min
Cold normal: 20 l/min

At the showerhead;
Hotwater: 2.2 l/min
Cold restricted: 1.8 l/min
Cold normal: 10 l/min

Is the flow rate for the hot poor, or the cold flow rate excessive? Have I missed anything? I hope the numbers etc help, I'm an engineer so I love a little bit of data!

Many thanks in advance.

Ian

 

[xr4x4]

why dont you just fit a new point to the tank in the loft and run your bath tap off that?

that will balance the hot and cold then.

then you could pump the supplys and have a really good shower.

 

[electronicsuk]

9.1L/min from the hot tap isn't too bad for a gravity system, especially if the bath is upstairs and there isn't much distance between the hot outlet and the water level in the CWS tank.

Your problem with the shower wouldn't be fixed even if you could get more hot water flow, as it's caused by the difference in pressure between the mains and gravity supplies. The correct solution is to bring a new gravity cold feed from the CWS tank to the bath cold tap, or convert the DHW system to pressurised, whether that be by having a combi boiler installed or an unvented cylinder.

 

[wimper]

Thanks for the quick an honest replies. I thought the pressure differential was going to be the issue.

When I refit the bathroom the plan was always to fit a separate thermostatic mixer shower and then twin taps on the bath, rather than a mixer.

I am considering one of these;

http://www.tritonshowers.co.uk/digital-showers/satellites-sirona-mellena.aspx

as I really want a deluge style head, and a standard shower head for those hard to reach places! The addition of pump and the location in the attic will make it easy to add an additional feed from the tank in the roof. Or maybe a second tank so it doesn't empty too quickly.

2 further questions;

1) what are peoples opinions of Triton (build quality etc).

2) can I take the hot feed from the overflow of the hot water cylinder? ie the pipe that goes up off the T piece (I will T of again). Or will I have to run another pipe to the attic?

Cheers again,

Ian

 

[SimonH2]

As electronicsuk says, it's a problem with pressure differences, not flow rates - though the two are related.

You need to take your hot and cold feeds for the shower from points that have the same pressure - and that are ideally affected the same by external effects such as someone else running a tap.

You need to take a cold feed either from the header tank, or from the pipe where it feeds the bottom of the hot water cylinder. You want to take the hot feed from the pipe coming out of the cylinder and as close as possible to the cylinder. They even make some spacial fittings that connect two pipes to the tank in such a way that the flows don't interfere with each other.

If you use an independent feed from the header tank, then someone running a hot tap will slightly reduce the pressure at the cylinder and your shower will run slightly cooler - the water flow through the feed pipe causes a pressure drop. Taking your cold feed from close to the HW cylinder will mean the pressure drop affect both hot and cold supplies to the shower and the effect is reduced.

 

[Axel]

You didn't specify the make and model of the iron in picture 2.

That electrical junction box shouldn't be on the floor - best attach to the wall in case of a leak.

 

[wimper]

You didn't specify the make and model of the iron in picture 2.

That electrical junction box shouldn't be on the floor - best attach to the wall in case of a leak.

Cheers for that, it's a good point about the junction box. I'll have a look at moving it.

And wrt the iron, apolgies for scrimping on the detail.... It's a Tefal Azur 50!

With regards to fitting a pump, is it essential to fit a No stop Essex flange to the cylinder? There seems to be varying requirements...
Ian

 

[BingoBongo]

i cant really tell from the pics but is that a gravity or fully pumped iron

 

[Axel]

This particular iron has a 2200 Watts element able to drive 40g/min constant steam output, 90g/min shot of steam/vertical steam. There is a 350ml water tank capacity, an integrated scale cleaner, extra calc-clean system, drip stop system and 2.4m cord length.