Just had a new hot water tank fitted (not brave enough to DIY) and it is fine. Hot water is hot etc., but hot water now takes much longer to reach the taps than it did with the old tank. The pipework all looks the same, so is there any logical reason? Tank and boiler stats have not been moved. Not a problem as such - there is plenty of hot water, and at the right temperature, it just takes a long time to arrive.
The old tank would have been at least thirty years old. Have tank designs changed? System is entirely conventional. Oil fired boiler feeding hot water and central heating. Not a combi boiler.
My thoughts precisely, but dead easy to test by feeling the pipes at the top and bottom of the tank as you draw off water at a sink, even if it's not obvious from inspection alone.
One possibility is that better insulation keeps the heat better localised in the tank, whereas previously more of the attached pipework close to the tank may have had a chance to heat up.
There may be some crap got down the pipework when they removed the old tank. It may be possible to clear it by linking hot & cold (mains pressure) taps with a bit of hose. Secure assistance and hold the hose against the tap outlets by hand with a bit of rag to help seal. Turn hot tap on first. Also clears any airlocks.
Do you mean that you now have to run off more cold water before the hot arrives, or that the flow rate is slower?
As explained it would be worth while checking that what should be the cold feed pipe towards the bottom of the tank does not get warm when you draw off hot water.
This is by way of a test, really, as I sent a more detailed reply earlier, that does not appear to have arrived yet.
To clarify, the flow rate is fine, as is the hot water, when it arrives. The problem is that we have to run off far more cold water than before, before the cold water becomes warm then hot.
What I am really getting at, is could this be because of a new tank design or some such, or should I ask the plumber to have another look. The new tank certainly has more insulation around it than the old one did.
Sounds like you should get him back. If nothing else was changed the hot water should arrive as quickly as before. As Brian suggested, maybe he's cocked up the tank connections and is drawing water off from the bottom of the tank rather than the top.
Thanks Tim. I hear exactly what you say, and will certainly have a word with the chap, but I struggle to see how he could have mangled the pipes. This house was last replumbed in the 70s, and I can see exactly where he has used a few inches of new pipe, directly from the tank, then joining to the old pipe, which is obviously old, whereas the new is, well, new. Shiny.
Most odd.
I posted the following earlier today, but it seems to have disappeared.
Thanks, everyone. There was indeed air in the system when we first used the hot water after the new tank was installed, with much gurgling and spluttering at first, but that soon cleared.
Regarding changing pipe size, I don't think so. The only new pipe work is a few inches from the tank to the existing pipes. I should have taken a photo first, I suppose, but it didn't occur to me.
There are five pipes connected to the tank.
Right at the bottom, on the left, must be the incoming cold.
On the right, two connections, which must be the central heating. Bottom pipe (return to boiler?) is just above the level of the incoming cold. The other pipe on the right is, I assume, flow from boiler. About half way up the side of the tank. They are both 22mm, or possibly 28mm.
There is a pipe exiting the tank at the top, apex of the tank, which is presumably hot water to taps.
The fifth pipe is also on the left, exiting the tank at the side, but just below the top of the tank. 15mm. Where does that go?
Possible I suppose and v easy to check, just put a hand on the inlet pipe at the bottom of the cylinder and if it is warm with the hot tap is on then summut is up.
An outlet below the tank top is often used for a HW supply for a pumped shower. This helps to prevent it drawing air down the expansion pipe. Do you have a pump?
The only other thing I can think of is that your expansion pipe might actually be dipping beneath the surface of the water in the cold header tank. In this situation it's possible for cold water from the header tank to be drawn down the expansion pipe an I to the HW system, particularly if there's any obstruction in the tank inlet.
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