F & E Tank Question

[D_Hailsham]

I'm not sure what you mean by one or two inches above the feed to the C/H system.
Do you mean one or two inches above the outlet pipe on the F & E tank, so the f & E Tank should be near empty?

Yes.

Once the CH is filled up, there should not be any more need for water - unlike the Tank which supplies cold water to the HW cylinder and the toilets etc. The level need to be high enough to stop air getting into the system but not too high, as the level will rise as the water in the system heats up and expands.

It's the distance between the water level when cold and the overflow which is important. If it is too small the water will expand on heating and some will escape through the overflow. When the water cools down the level will drop. the valve will open and more fresh water will be admitted, reducing the concentration of the inhibitor. Over time there won't be any inhibitor in the system - just plain old tap water.

The volume of water in the system is approximately 6.5 litres per kW of radiators. The water will expand about 4% when heated so you can work out the minimum space you need to leave between the cold water level and the overflow to allow for expansion.

 

[kev999]

The thing about the flow and return pipes is that the TRVs were on the correct ends before I had the pipework changed for the new boiler.
Is it possible for the flow and return pipes to be connected to the boiler wrong?
Why should the original return pipes get hot before the flow pipes?
Thanks

The connections on your new boiler are on the opposite side from your old boiler. My guess is that the plumber found it easier to connect them the other way round. Provide the pump is pumping away from the boiler, it does not matter which pipe is the feed and which the return.

You say you have new TRVs. Most new TRVs are bidirectional, so they can be fitted to either flow or return. Just check that they have a double-headed arrow on them.

With a system as big as yours you may still have air in it. Open all Lockshield valves completely (make a note of how many turns are required so you can reset them later ) and remove all TRV heads. Then lock each zone valve in the open position (usually marked MAN).

Now bleed each rad with the water cold.

When that is done, set the zone valves to AUTO and turn one thermostat up so its zone valve is open. Now run the system while you watch the water level in your F/E tank (The level when cold should be about one or two inches above the feed to the CH system. If it is any higher, the ball valve needs adjusting to lower the ball.)

If the level does not change, then that zone is not leaking.

Turn down the stat and repeat for each of the other zones. This will identify which zone, if any has problems.

When you have sorted the "leak" out, you will have to reset the lockshield valves, which should be easy if you wrote down how many turns you opened the valve

I have done as you advised and at first test the upstairs zone was run for 45 minutes and I never seemed to lose any water from the tank.
I run the downstairs zone for 45 minutes and there has been a drop in the water level in the tank.
I see no leaks anywhere downstairs.
I will do this test a couple more times over the weekend to make sure it is correct.
Why would the level slowly be going down when the Boiler is not on, therefor the zone valves are closed to the downstairs, is it because the system still has air and is settling?
Is it looking like I have a leak somewhere under the concrete floor?
My House is quite old (1936). The exact same house next door has suspended wooden floors downstairs, mine has concrete. A neighbour who has lived in the close seemed to remember that the House had dry rot at some time and thinks the floors were ripped out and concreted.
The Central Heating was put in about the 1970s. I don't know how the floor was put on top of the central heating pipes. What I mean is I don't know if they are buried in the concrete or go down under a suspended concrete floor. Anyway I have not found any damp patches coming through the concrete anyway.
Without finding the leak coming up through the floor I don't think I have any chance of finding it.
Anybody got any ideas?
I have only lived in the House for six months and the Boiler water Jacket split after three months, hence the new boiler and pipework update.
Before the Boiler busted I was getting a lot of air in the main bedroom radiators, when I say a lot of air, maybe in five hours I would have to bleed it three times.
Was this a sign that the system was sucking in air at the point where I may have a leak under the concrete?
I'm really getting worried can anybody put my mind at rest?
Thanks

 

[kev999]

Just giving you an update.
Checked Tank level this morning and the tank had lost about 15 gallons.
Filled it up again and run upstairs zone again this mornig for half hour. Water level went up a little then 3/4 hour after switching heating off the level has settled back to before I turned heating on. I wll leave the heating off now to much latter today to see if it drops as much as it did last night. Then I will try the downstairs zone again.

 

[D_Hailsham]

Checked Tank level this morning and the tank had lost about 15 gallons.

But the tank should not have that much water in it when cold. It should only be about an inch or two above the bottom outlet. How high are you filling it?

Presumably you mean the level had dropped by 15 gallons (68 litres) or was the tank actually empty when you checked it and you had to put in 15 gallons to bring it up to the cold level. If it was purely due to the water cooling down, you would need to have about 260kW of radiators in your house to account for the drop. I know you said, in another post that you had a large house with many radiators, but 260kW is a hotel, not a private house!!

Sounds as if you definitely have a leak somewhere, probably under the concrete floor!

Filled it up again and run upstairs zone again this mornig for half hour. Water level went up a little then 3/4 hour after switching heating off the level has settled back to before I turned heating on.

That sounds OK. I take it you are filling up to just above the bottom pipe.

 

[D_Hailsham]

Some Hire shops, e.g www.hss.co.uk, hire out damp meters. They are mainly used for detecting rising damp in walls, but they should be able to detect damp in your concrete floor.

If that fails then these people should help Leak Busters

 

[Softus]

Thank you for taking the time to give comprehensive information.

I have 24 Rads on it, 11 downstairs 13 upstairs. (Sounds like a lot of rads but I will only have half of them on at any time, My Cylinder is approx 1100mm high.

In that case you have absolutely no need for an F&E cistern as large as 20 gallons, let alone 25.

I have been told maybe the system still has a lot of Air in it and it is settling down. I have bleed the rads, would the tank level drop steadily until all the air is out?

Yes.

It's not wise to keep the supply to the F&E shut off, especially since it's not just you working on the system.

I can see no evidence of a leak.

It's possible that you don't have a leak, in which you're fretting about nothing.

I will be phoneing the Plumber Monday to get his advice, I just wanted to try to work out where the water is going before I contact the Plumber.

I would turn on the supply to the F&E and leave it on. When the system has been vented, and run, and vented again, and run again, then you can judge whether or not water is still being admitted to the F&E cistern.

On a general point, the testing you're doing should be carried out by the boiler installer. He should be able to pressure test the pipework, commission the appliance, decide when to add corrosion inhibitor, vent the system, declare it all working, leave you with user documentation, and explain the warranty. If there's a leak resulting from what he's done, then he is then liable.

If you keep fart-arsing around by turning supplies off and on and venting and looking for leaks, before he's finished the job, then you're wasting your time.

 

[larrytheleak]

The thing about the flow and return pipes is that the TRVs were on the correct ends before I had the pipework changed for the new boiler.
Is it possible for the flow and return pipes to be connected to the boiler wrong?
Why should the original return pipes get hot before the flow pipes?
Thanks

The connections on your new boiler are on the opposite side from your old boiler. My guess is that the plumber found it easier to connect them the other way round. Provide the pump is pumping away from the boiler, it does not matter which pipe is the feed and which the return.

You say you have new TRVs. Most new TRVs are bidirectional, so they can be fitted to either flow or return. Just check that they have a double-headed arrow on them.

With a system as big as yours you may still have air in it. Open all Lockshield valves completely (make a note of how many turns are required so you can reset them later ) and remove all TRV heads. Then lock each zone valve in the open position (usually marked MAN).

Now bleed each rad with the water cold.

When that is done, set the zone valves to AUTO and turn one thermostat up so its zone valve is open. Now run the system while you watch the water level in your F/E tank (The level when cold should be about one or two inches above the feed to the CH system. If it is any higher, the ball valve needs adjusting to lower the ball.)

If the level does not change, then that zone is not leaking.

Turn down the stat and repeat for each of the other zones. This will identify which zone, if any has problems.

When you have sorted the "leak" out, you will have to reset the lockshield valves, which should be easy if you wrote down how many turns you opened the valve

will not each zone be fed from common return pipes & so you will learn little about the water loss if there is any

 

[D_Hailsham]

will not each zone be fed from common return pipes & so you will learn little about the water loss if there is any

The length of return pipe common to both zones will depend on the layout. With separate downstairs and upstairs zones there will only be a relatively short length of return common to both zones.

I have been told maybe the system still has a lot of Air in it and it is settling down. I have bleed the rads, would the tank level drop steadily until all the air is out?

Yes.

It's not wise to keep the supply to the F & E shut off, especially since it's not just you working on the system.

Thanks, Softus, for realizing something which should have been obvious, i.e. how did the OP know that the level was dropping by 15 gallons?

Edit:

However, I can see the OP's dilemma. If he leaves the supply to the F/E tank on and there is a leak, he will never know until it is too late as the tank will be kept topped up automatically (though the sound of the tank continually filling would be a clue).

By doing it his way he can tell how much is being "lost", though whether it is due to a leak or just the system slowly losing the air which entered when the boiler was changed, is not easy to determine over the net.

One thing which has not been mentioned is flushing? Did the OP have the system flushed before the new boiler was fitted and, if so, was it a power flush and what chemicals were used? This could have found a weakness in the buried pipes.

 

[kev999]

Thank you everybody for your advice.
As to the Power flushing, no I did not have it power flushed before the Boiler was fitted.
I do know that it says I should have had this done but before the new Boiler was fitted I had taken every Radiator off as I was putting the TRVs on and flushed it out with a hose. Not a Powerflush I know but right or wrong I decided not to have the Power flush.
I'm convinced that I have a problem some where with a leak but I'm not a Plumber.
I understand what was said ealier post abot the F&E tank only having couple of inches water above the feed pipe but I have left it with much more water in at the moment just so I can see how much it is going down.
If there is a leak then it is nothing that the Plumber has done because he was only doing pipework around the boiler and there is no leak there.

I will be calling the Plumber and asking if he can do somekind of pressure test on the pipework.
If a leak seems to be found and it looks like it's below the concrete then I will be contacting my insurance to see if they can be of any help before I do anything else.

I will keep you updated and let you know how I get on.
Thanks for the advice