Header tank flowing wrong way?

[kevplumb]

oh s**t not a tradesman he will catch us out

 

[davidf]

1. Boiler is Potterton Profile, gas.

The boiler is wall mounted on the ground floor. The hot water tank is also in the ground floor, at floor level. Both heating and hot water are pumped with an electric valve on the downstream side of the pump. The pump and control valves are in the cellar beneath the boiler and hot water tank.

The house is 3 stories with 21 radiators. The header tank is in a side loft only just above the level of the top floor radiators.

2. When the pump is running, water flows continuously UP the expansion pipe from the header tank.

3. Pump changed about 2 weeks ago. Just before that I changed the washer on the header tank valve as it was overflowing. However, the new washer did not cure the overflow so I have today changed the valve.

4. I don't know when the problem started - I only discovered it today after fitting the new valve.

5. Water flows continuously whenever the pump is on, even when the boiler isn't firing, when heating or hot water or both are on.

Otherwise the system is running fine. One of the radiators - the one nearest the pump etc - needs venting every few months but otherwise no problems. (Hot water circulating through the header tank isn't really much of a problem except that it suggests to me that something isn't quite right!)

Is there anything else you need to know?

 

[brumylad]

2. When the pump is running, water flows continuously UP the expansion pipe from the header tank.

3. Pump changed about 2 weeks ago.

Is there anything else you need to know?

1. Just to clarify then, water is continually running out from the pipe wich arches over the header tank when the pump is running.

2. Is the new pump a 15/50 15/60 etc. what number is it set on

 

[oilman]

I could never have imagined your system would be like that. A possible problem is a blockage, but we need to know where the feed pipe is connected to the system.

 

[davidf]

brumylad & oilman: yes, water is flowing up the pipe which arches over the header tank - spooky eh?

I'll have to poke about a bit to get the other info. I'll also double-check all the radiators are working. I'll get back to you.

 

[oilman]

The pipe over the top is the safety vent, the feed and expansion is the one that delivers water to the system.

 

[davidf]

The pump is a 15-60. It's set to III (maximum).

 

[brumylad]

personally I would turn it down to II and recheck the header tank.

Wait and see what the others say.

 

[oilman]

...... we need to know where the feed pipe is connected to the system.

We need to know the sequence of pipes from the boiler flow to the vent, feed and pump. There may be a blockage where the feed pipe meets the system.

 

[davidf]

I've turned the pump down to II - it makes no difference.

The pipes are i bit hidden - it'll take me a while to trace them. I'll get back to you when I have.

 

[davidf]

Just one question - the water can only flow up the pipe because its end is below the surface. Should it be? Could that be starting a siphoning process? If it were out of the water, would it just suck air in?

 

[brumylad]

thats correct the vent pipe should not be submerged.

Alter the level of the new ball so the valve closes when the header tank is about 1/4 full with water.

you will first have to remove some water by hand, obviously.

 

[davidf]

I've just done a test - I've introduced air into the 'arch'. That's stopped the siphoning and water no longer flows up the pipe.

I have a theory. I think that, while the ball valve wasn't working, the level got so high that the arch got full enough for a siphon to start and, once started it wouldn't stop. Because of lack of space the arch isn't very high above the water level.

I can't adjust the ball valve - it's already as low as it will go. I think I'll just chop a bit off the bottom of the pipe.

Anyway, assuming that works, thanks everyone for your help. I promise never to call plumbers 'overpaid cowboys' again!

 

[kevplumb]

could try raising the hight of the expansion (yeah the old mans woke up again)

 

[oilman]

I can't adjust the ball valve - it's already as low as it will go.

Either the tank is very deep, or the ball is operating near the bottom of the tank, or the arm needs bending. There should be around 4 inches of water above the outlet pipe, and the vent pipe should not go below the overflow pipe.