Low hot water pressure?

[jimmy1999]

I'm in need for some advice.

We have been living in the house for nearly a year but never have the hot water on because it's at such a low pressure only cold comes out the mixer tap in the kitchen.

I completely renovated the house before we moved in but it's the same heating system. Gravity fed with the tank in the loft and water cylinder in the bedroom on the first floor. When I first turned it all on the bath hot water only trickled out really slowly. So from reading other posts I pumped the cold mains through the hot system using the two bath taps. This improved the pressure but it's still not great.

It's so low that when I use the kitchen tap only hot comes out. I tried to reduce the cold pressure but it has to be really low to let any hot out.

Does anyone have an idea what to try next? I hope it's a block in the pipe rather than not enough head but I don't no how to work out?

Any help on this would be so useful it's getting silly having to boil the kettle to do the washing up ect.

 

[kirkgas]

your hot water pressure should be 0.1bar per meter of height between the water level in the loft tank and the tap, in general most houses have the tank in the loft and have adequate pressure, so start with the basics check the flow into the tank to ensure it is a good pressure, next check the valves are fully open, you might have a valve at the outlet of the tank in the loft, and/or at the base of the hot water cylinder, it can be difficult to confirm if the valves are open or shut if the inside of the valve is broken, so the next best way will be to phsically check the valves are fully open, so you will need to fully drain the loft tank then the cylinder (which must be drained from the drain valve at the bottom, DO NOT REMOVE THE VALVE AT THE CYLINDER UNTIL IT IS DRAINED) if the cylinder isnt drained the water will reverse flow from the cylinder out of the valve and flood the place, if the valves are ok there could be a blockage in the pipe somewhere which will take a bit of investigating, once you have checked/repaired the valves refill and check what pressure you get then

 

[jimmy1999]

Thanks for your reply. I have drained all the system and started looking through all the valves and I think I have found a blockage. I will try add a photo

cid:A0FBFC66-E967-412A-98C9-5A8AED6617B6/IMAG0072.jpg

This is on the top of the hot water cylinder which is the hot feed out I think?

I have removed this now and replaced the pipes but just wanted to check you think this could be it as draining the system took me a while. Thanks for the advice.

 

[jimmy1999]

Ok doesn't look like it worked. The picture showed inside the outlet at the top of the tank about half the outlet was blocked by what looked like the same material that is insulating the tank.

 

[TicklyT]

....I completely renovated the house before we moved in...

Did your renovation include new taps, and are those taps suitable for a gravity system?

Many taps on the market are only suitable for use on high pressure systems, such as unvented cylinders or combi boilers.

The minimum working pressures are usually marked on the packaging or in the installation instructions. Brassware suitable for gravity systems is usually rated at 0.2 or 0.5 Bar.

Taps with a minimum working pressure of 1 Bar will nearly always give a disappointing performance if used on a gravity system, where pressures rarely exceed 0.5 Bar.

The hot water pressure you have available is equal to the height difference between the base of the COLD storage tank and the tap outlet, measured in Metres and divided by 10.

 

[jimmy1999]

I did get new taps so had to hunt down the manual that came with them. It says they are suitable for a min pressure of 0.3 bar. So that would only be 3m head which I easily have. I guess it does depend on the cold pressure though.

I will fill it all back tomorrow and hope the blockage in the tank was the problem. Has got me thinking does that mean my Cylinder is leaking? I can't work out how the insulation stuff would get on the inside of the tank.

 

[jimmy1999]

Ok I have filled it back up but unfortunalty no change in the pressure.

I have showed the photo to a plumber and he inks it's limescale. He said I should try take the cylinder outsidenand wash it all out but by the sounds of it I will still have a block in some of the pipes.

Does taking the cylinder out sound like a good idea? I guess for that I will have to drain the heating system aswel.

Any advice would be useful I'm getting a bit stuck?

 

[jimmy1999]

Ok I took out the hot water cylinder. It was completely full of limescale, I gave it a good wash out with a hose. I then connected it all back up and filled it up.

Seemed to be working well then I turned the hot tap off on the bath, when I turned it back on it's back to how it was before. I have tried clearing the pipes with mains cold again and had a look at the hot outlet on the cylinder and no difference.

Any ideas I'm completely stuck, looking like I might have to get a plumber but would they try anything I haven't?