gravity fed hot water - lack of

[jezzer99]

Hi,
When I run basin taps or a shower things are generally Ok but when I fill the bath I seem to get cold water out of the hot tap even though the HW tank is full of HW. I've been up in the loft and found that the end of the HW overflow pipe is submerged in the CW tank, and, when the bath is being filled, cold water is being syphoned from the CW tank thru this overflow rather than HW from the HW tank in the airing cupboard below.

Not sure what is happening, but I guess its because there is a blockage and the HW tank can't fill fast enough when a bath is being run, causing the syphoning to kick in. I have tried lifting the overflow pipe above the water level, and the bath fills sooooooooo slowly but it is hot.

Suggestions and advice as to what I can do about this gratefully received.

Thanks
Jezzer99

 

[TicklyT]

The vent pipe should be clear above the water in the cold storage tank

Check the outlet from the cold tank isn't blocked by any 'foreign bodies', bits of stray insulation etc.

Also check any valves in the cold feed to the hot cylinder are fully opened.

 

[jezzer99]

The single gate valve is fully open and there is nothing blocking the outlet from the tank. When the bath is filling I can hardly feel any draw when I put my hand over the CW tank outlet to the HW tank below. Obviously there is enough to service the shower.

I was wondering whether there might be crud in the bottom of the HW tank, cant think why though. Its a 30 year old installation.

I was thinking of getting the CW feed to the HW tank pipe replaced. Maybe that will fix it.

 

[dextrous]

Either physically lift the end of the vent pipe clear of the water, cut it clear, or (more easily) adjust the height of the ball float to lower the water level.

 

[jezzer99]

I've done that, although I wasn't sure if there was a good reason for it being submerged. Presumably, the syphon wouldn't happen if the hot tank filled faster. Now I'm trying to understand why the hot water flow is so poor that it takes ages to fill the bath.

 

[Nige F]

mouse skull in the pipework ...seen it wiv` me own mince pies 30 year old setup probably never had a proper lid/lagging jacket (...let alone a sealed, screened vented lid ..cuz it wasn`t required then)

 

[Agile]

Is the ball valve leaking or correctly sitting on top of the water?

Obviously something has changed!

Is any valve by the cylinder on the cold feed fully open?

Tony