Small tank in loft, pipe is ejecting water

[britainsgottalent]

I hope someone can help us?
Our pipe over the small tank in our loft has water coming out of it. It is only slowly, not a massive gush, but we have noticed it today. Why is this? Can we fix it? We have a potterton boiler, 2 tanks in the loft, a hot water tank in the airing cupboard, there is a red pump near the cylinder and a silver cased box with pipes going into it also near the pump. Why is the happening?

Thank you for taking the time to hopefully help us.

 

[mogget]

This is a pump

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• mogget
• 24 Feb 2009
• 2

These are motorised valves

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• mogget
• 24 Feb 2009
• 2

I'm assuming you mean the vent pipe which is a pipe that goes 'up and over' then back down into the tank.

Turn the heating and hot water off - does the flow stop?

 

[britainsgottalent]

Hello.

Yes the pump is that shape, but red. And the motorised valve is like that (same colour) but with a connection into the bottom also. Yes the pipe (vent pipe?) goes up and over into the small water tank.
Strangely enough this only happens when we put the h/w on at the programmer. the water coming out is mildish, not stone cold but not really really hot. Do you have an idea what the fault could be please?

 

[mogget]

This is called pumping over and isn't good for the system.

What speed is the pump set to - usually there are three speeds.

Would it be possible to post some pics of the pipework around the cylinder, pump and motorised valve?

 

[britainsgottalent]

Hi

The pump is on setting II (2) - i don't have a camera, but can desribe them the best i can - a pipe comes up from the floor and carries on up (to the small tank) and then a small section of pipe joins this and a smaller diameter pipe comes down (also from the small tank), and joins the larger one, this then joins to the pump, then the silver casing motorised valve, then a branch into the hot water tank, and the other side goes down through the floor (to the radiators)???

 

[mogget]

I think I know what you mean, but I'm not sure. Can you confirm / explain / elaborate?

Look on the side of the pump housing and you will see an arrow - the water flows in the direction the arrow is pointing.

Can you describe what tees and branches can be found around the pump and valve, in terms of which fitting the water encounters first?

The usual set up is:

Boiler-----------Vent pipe-------cold feed---------pump-------3-port motor valve

The vent pipe is the one that goes up and over, usually 22mm diameter.

The feed pipe is the one that goes to the bottom of the f&e (small) tank, 15mm usually.

 

[britainsgottalent]

Hi

The pump arrow is pointing down, so water is pumping/flowing into the direction of the silver cased motorised valve.

The larger pipe, is going over the small tank, the smaller, coming from a connection at the bottom of the small tank. these two pipes, in the airing cupboard, and before the pump, have a short length of pipe (about 4" long) joining them also. THe smaller pipe then enlarges again and goes to the pump.

Is this normal?

WHy is the pumping happening?

 

[mogget]

OK, so you have the usual setup - the pipe that connects the vent pipe to the feed pipe - what size is this pipe? 15mm? 22mm?

 

[britainsgottalent]

that pipe is of the larger size, same as the vent pipe

 

[mogget]

There are two reasons I can think of that may be the cause -

1) The pipe between the vent and feed may be blocked with crud,

2) The vent pipe doesn't extend high enough before turning back downward to the tank.

Or a combination of the above.

How far above the top of the small tank is the arch of the vent pipe?

 

[britainsgottalent]

the arch? the pipe bends high up and then goes down into the tank through the hoe in the lid. this problem has only been recent.

 

[mogget]

Sounds like crud accumulated at the bottom of the vent pipe then.

Do you have a magnet? If you have, you can see if it's attracted to the suspect area, as the crud is usually iron oxide.

 

[britainsgottalent]

i have a magnet - i will try it.

 

[britainsgottalent]

yes the magent pulled quite strongle on the short piece of pipr, and it also was less attracted to but still a slight pull to the other pipes near the pump and motorised valve.

 

[mogget]

OK... the pipe between feed and vent is partially blocked. This is causing poor flow and the water is trying to go up the vent pipe because of the increased pressure.

The system needs a good flushing and cleaning IMO. You can find information in the faq about how to do this, using chemicals such as Fernox F3 or Sentinel X400. I suspect that you may need to renew the pipework where the blockage is though, as it can be hard to shift.

If it were my system I would renew the pipework where the feed and vent join, then circulate x400 for a few weeks before draining down, flushing the rads, and refilling with fresh water and inhibitor.