I suspect that what is happening is the water in the cold header tank is falling below the outlet to the cylinder on occasions thus causing an air lock.
Check out the water level in the cold tank and raise it if it is on the low side.
It may be slow filling due to a blockage in the ball valve (very common).
Check also the size of your tank. Less than 50 gallons can be a problem sometimes.
Time to get dusty and get up in that loft.
Minor annoying niggle - the hot water tank doesn't appear to refill completely, and over a period of time leads to sputtering hot tap, reduced flow and complaints from the Trouble 'n Strife that "the 'ot waters playin up again!" because the bath takes an age to fill.
A quick-fix is to feed-back some mains cold into the hot system via my hand over the outlet of the kitchen mixer tap. Keeps her quiet for a week or two - until the problem comes back.
I have also on one occasion, done the same via the washing machine feeds, thinking "this'll sort the b#*tard out good 'n proper". Nearly twenty minutes later with the tank finally full, the overflow was gushing. It was sorted - for about a month when once again I got "the 'ot waters playin up again".
The rest of the CH & HW works ok, according to the demands of the family; the rads are all hot, there is no sludge in the system as far as I can ascertain, the pump and boiler all work on que and the supply valve has only just been replaced. The majority of the system is less than 10 years old, with the boiler going into the loft to replace the archaic Potterton that used to have pride of place in two thirds of the kitchen.
Before resorting to professional help, I would just like to know if there is anything else I can possibly do about this myself? Any ideas? Anyone??
TIA for anything forthcoming.
Chris L
skype:kitchenmanuk?add
Sounds to me you have a high point in flow from the tank to the taps, if it is only the bath then just trace the pipe, find the high point & alter the pipework. If that is the problem send the bill to the 'plumber' who did it.
If the tank is not filling properly you need to look at the float valve in the tank. Either it's shutting off too soon leaving the level too low, which means adjusting the level, or the flow is reduced by limescale build-up. Is the valve brass or plastic, and how is the level? try moving the float up and down in case it's seizing up. And look in the bottom of the tank, are there chunks of limescale over the outlet, reducing flow that way?
Steve
ChrisL,
As well as limescale over the outlet (as already suggested), try looking for loft insulation, general detritus or even bits of a dead bird/mouse that could be floating around and intermittently block the outlet - as well as a possible airlock somewhere in the system.
BTW. the hot water and C/H are two different systems within the cylinder but usually use separate header tanks - note: *usually* there are exceptions.
Brian G
I will lay my life that you have pipework which rises at some point from the hot tank before it falls to the basin. Air gets trapped in the top of this rise and after a while prevents water flowing. Either bend the pipe downwards so that there is a fall ALL the way along the pipe, or cut it at the high spot, install a tee and an open pipe which reaches to a height above the header tank, putting a walking-stick handle bend on the end to keep much out.
Rob Graham
Many thanks for this, and all the other responses. I know what I'll be doing this weekend. Very much appreciated one and all!
Chris L
Well,having been in the loft this morning, I can confirm that the tank is OK, and the water level is at 75 - 80% full with the ball valve operating as it should. I tied the ball valve up to empty it a bit and then on release it worked ok with a good flow which cut off gradually as one would expect. There was no evidence of any great amount of silt or grit in the bottom of the tank, nor were the outlets clogged in any way (2 - 3 inches above the bottom of the tank as they should be). The tank itself is about 4ftx3ftx4ft and looks to be the original from when the house was built about 45 years ago; still in good nick for all that as the integrity appears ok and the top is still in one piece.
Were you actually experiencing flow difficulties at the time? If not, then there may not have been much wrong to see.
There is a bit of a difference between the float being held up with string and dropping several inches in one go when released, and a float slowly falling with the water level.
A bit of dirt and corrosion plus a bit of wear, and there may be a point where the valve can stick and not open fully, when the ball falls slowly. The mechanism is not exactly precision engineering..
If you weren't experiencing flow problems when you went to look - you could leave it until you are and then see what the level is.
I would be tempted to simply replace the valve assembly with new, anyway. It is (usually) one of the cheapest and easiest plumbing jobs. If it fixes the problem, fine. If not, at least you know that it is ok and shouldn't need looking at for years. And won't fail with water pouring out the overflow when all the shops are shut for Christmas and you have other things that you need to be doing..
skype:kitchenmanuk?add
before changing the float valve wait until you have problems again THEN check water level in the tank, if it is OK then you have a high point as I and another have suggested. Don't fix anything until you are sure it is broke
kitchenman
Yes- I am not fixing it 'cos it ain't broke. I watched the tank empty and then watched it refill - tedious job, but I knew I had to watch it through the whole range of motion and movement, up and down. It appears to work OK, and I don't think the refill rate is an issue given the size of the tank.
I am tending to think it is either an impartial obstruction in the h/w tank inlet pipe, or an issue with the pipe run as suggested elsewhere. Not sure it is the former, as despite my poking around when the tank was empty, there has been no sediment or crud evident when refilled and I turned the taps back on. Surprising as it may seem, there simply isn't that much sediment in the tank - at most I would think less than an agg-cup full if you were to sweep it up! (we live on the clay).
So - we still have incompetent flow from the hot taps today; and a quick feedback from the cold tap (even from the indirect supply via the bath mixer tap, and not the mains) seems to sort it out temporarily. I am therefore tending to support the latter theory now, and will be looking into this just as soon as I get the time.
Thank you all for your extremely helpful input and taking the time to post back. As it is now Advent, I wish you all the best the season can bring!
Chris
Chil7th,
Now that you have 'cleared' the ball valve and rubbish in the tank of causing problems:
If you don't want to resort to 'taking things apart' at this stage, I'll pass on an old plumbers trick - when the hot water 'stutters' again, connect a short length of hose pipe from the cold water tap (mains pressure) to the hot tap, open the hot tap fully and then turn on the cold tap with just enough pressure to force the hot water back into the tank - have someone up in the attic just to keep an eye on things so that the tank does not overflow.
One of two things will then happen :
1 - After a short while, any airlock will clear and the hot water will run normally - if the problem recurs, then start looking for a 'rising' h/w pipe somewhere in the system. 2 - It should clear any ' loose foreign body' that has somehow found its way into the pipe and is 'rattling' around somewhere on a bend - if that fails, then it may be time to start dismantling pipe sections to have a look inside.Please note, I am not a plumber, just an old maintenance foreman who has dealt with this sort of thing in the past and seen this trick used by the 'professionals as a last resort - and you try it at your own risk.
Best of luck
Brian G
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