Expansion pipe flowing.

[Tosh]

Hi all,
I've just installed a single impellar pump for a guy who has very low pressure on his hot water.
The storgae tank is downstairs under the stairs with the CWSC and F/E tanks up in the loft.
Because the storage tank is under the stairs there is no expansion pipe coming off the top only the hot feed. The expansion comes from somewhere else along the line, possibly inside the chimney with the back boiler. Because of this every time the pump turns on it pumps all his hot water straight up the expansion line and out into his CWSC. still leaving very little pressure at any hot tap.

Is this normal practise for a back boiler or just a bodge job and how do I get around it?😕

Many Thanks

 

[sonray ltd]

no it a bodge job and needs to be sorted.
hows air going to escape from the cylinder and out the vent if it can't get to the vent.

as for your poor flow i wouldn't put it down to where the cylinder is, its the cws height that gives you your pressure/flow.

i would say he must have an issue with air as air don't go down hill to get to the vent pipe.

 

[Mike Jackson]

How have you fitted the pump? You could have seriously compromised the safety of the system if the pipe doesn't now continue rising from the top of the cylinder or you have fitted isolating valves.

Mike

 

[Tosh]

The hot water feed still comes out the top of the storage tank so I've fitted the pump in line from here. Got isolating valves either side of the pump for servicing etc.

The system does have an expansion pipe but it doesn't come out the top of the tank like normal. It's been put somewhere further down the line but it's built into the walls possible within the chimney where the back boiler is.

If I can isolate/remove this expansion pipe and put one back on the top of the tank, can I put it at an angle I.E 45 degrees to follow the angle of the stairs up. If It goes straight up it will go through the stairs (obviously can't dp that).

Many THanks guys

Scott

 

[Mike Jackson]

You've just created a potential bomb by putting isolating valves on the pipe out of the top of the cistern. If one of these is closed, the valve is closed on the cold feed and the boiler comes on there is nowhere for the expanded water to go and the pressure will build up in the cylinder and probably split the cylinder. If there is an immersion heater fitted and this is turned on and the stat fails you could end up with a cylinder of superheated water under pressure. If this then splits the water will flash to steam and expand it's volume around 1600 times.

This is obviously a worse case scenario but it can (and has in the past) happen. Have a look at YouTube - exploding hot water cylinder myth busters to see what happened when mythbusters tried it.

I know this is unlikely to happen but if anything did happen you will be held responsible. I would get round to the job andremove the pump as soon as possible.

Mike

 

[justlead1]

Hi. Did you investigate the probable causes of the problem Tosh.
I have been called out to many similar complaints, to find and old sock intermittently blocking the cold feed to cylinder. On one occasion a mouse down the cold feed and so on.
Essex along with white stilettos, is also known to have water that corrodes brass fittings, partially blocking pipes.
The effect it greater on the hot supply. However pumps, IF they must be fitted should ALWAYS be placed down stream of the vent/expansion pipe.

In the event of the gate valve on the cold feed being turned off and the isolating valves on the pump, any heat applied or draining off the cylinder would cause it to rupture. Good Luck

 

[Tosh]

It's starting to sound bad.
There has always been low pressure on the hot since the guy moved in hence why he wanted the pump installed.
There is no blockage anywhere the run is clear. The problem of low pressure is down to the CWSC being in the loft and the storage cylinder being downstairs under the stairs. The hot water then travels upstairs to the bathroom first before coming back down to the kitchen.
The Cylinder has no stat on it and the immersion heater has been disconnected because it doesn;t work.
The only way the water and CH are heated and controlled is via the back boiler inside the chimney.

Many thanks for this guys.

Scott