This is a message I posted in November 2013 :

quote 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 pipe work
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. unquote

Since then, nothing has changed in spite of plumber coming back saying
nothing wrong, me forcing cold water back through the hot water etc.

Yesterday, a couple of guys came and changed four radiators, fitted TRVs
and removed an old bath, basin and toilet, capping the pipes. Much
turning off of hot and cold water, partial draining of heating etc.
Today, the hot water is back to how it was before the new tank was
fitted in 2013. What have they done? Whatever the problem, they have
fixed it. All I can think is a valve somewhere was only partially open
(although flow was fine), and yesterday it was fully opened.

Delighted, but flummoxed.
--
Graeme

Used to get a similar problem at our old house after draining down the DHW due to partial air locks when refilling The simplest solution was to connect the washing machine hose cold feed to hot feed and give it a quick blast at mains pressure until water came out of the main tank overflow, problem solved.

Richard

On 27/04/2017 16:16, Tricky Dicky wrote:
Used to get a similar problem at our old house after draining down the DHW due to partial air locks when refilling The simplest solution was to connect the washing machine hose cold feed to hot feed and give it a quick blast at mains pressure until water came out of the main tank overflow, problem solved.

Richard

When we had the cottage in Langthwaite we had that problem every time
the system was re filled after the winter drain down.

Simple cure was to block the outlet of the kitchen mixer tap with a
thumb whilst both taps were turned on thus forcing cold back up the hot
pipe. Wait for gurgly noise, turn off.

Mike

On 4/27/2017 4:31 PM, Muddymike wrote:
On 27/04/2017 16:16, Tricky Dicky wrote:
Used to get a similar problem at our old house after draining down the
DHW due to partial air locks when refilling The simplest solution was
to connect the washing machine hose cold feed to hot feed and give it
a quick blast at mains pressure until water came out of the main tank
overflow, problem solved.

Richard

When we had the cottage in Langthwaite we had that problem every time
the system was re filled after the winter drain down.

Simple cure was to block the outlet of the kitchen mixer tap with a
thumb whilst both taps were turned on thus forcing cold back up the hot
pipe. Wait for gurgly noise, turn off.

Mike

My guess too, classic airlock problem with vented gravity systems.

In message ,
newshound writes

My guess too, classic airlock problem with vented gravity systems.

That is my only conclusion too, although I tried the suggestions by
Richard and Mike, holding my thumb over a mixer tap, and running a short
length of pipe from one tap to another. The second time I must have
left the cold forcing itself through the hot system for several minutes,
yet these guys did something yesterday which cleared it immediately.

--
Graeme

He did that already, but if an airlock and a partly closed valve was present
the pressure would not shift the aire in a pipe with a sag in it. It
happened to me some years ago.
Brian

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"Tricky Dicky" wrote in message
...
Used to get a similar problem at our old house after draining down the DHW
due to partial air locks when refilling The simplest solution was to connect
the washing machine hose cold feed to hot feed and give it a quick blast at
mains pressure until water came out of the main tank overflow, problem
solved.

Richard

On Thursday, 27 April 2017 15:36:27 UTC+1, Graeme wrote:
This is a message I posted in November 2013 :

quote 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.

Most of the lag is just the time it takes to heat all the copper fittings en route. The cooled water comes through fast. Have they taken some fittings off?

In message ,
therustyone writes
On Thursday, 27 April 2017 15:36:27 UTC+1, Graeme wrote:
This is a message I posted in November 2013 :

quote 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.

Most of the lag is just the time it takes to heat all the copper
fittings en route. The cooled water comes through fast. Have they taken
some fittings off?

No, the only change to the hot water was removal of a bath and basin,
the supplies to each being capped off. No changes to run length or
anything else, except turning the hot water supply off at the tank for
perhaps half an hour.

Tried again this morning, and first use of a hot tap results in hot
water arriving much quicker.
--
Graeme

On Friday, April 28, 2017 at 1:15:20 PM UTC+1, Graeme wrote:
In message ,
therustyone writes
On Thursday, 27 April 2017 15:36:27 UTC+1, Graeme wrote:
This is a message I posted in November 2013 :

quote 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.

Most of the lag is just the time it takes to heat all the copper
fittings en route. The cooled water comes through fast. Have they taken
some fittings off?

No, the only change to the hot water was removal of a bath and basin,
the supplies to each being capped off. No changes to run length or
anything else, except turning the hot water supply off at the tank for
perhaps half an hour.

Tried again this morning, and first use of a hot tap results in hot
water arriving much quicker.
--
Graeme

Is there a small hot-water leak somewhere? i.e. is hot water being leaking at some place between the boiler and the tap? This would dleave a shorter pipe run for the hot water to travel before reaching the tap

Robert

In message ,
RobertL writes
On Friday, April 28, 2017 at 1:15:20 PM UTC+1, Graeme wrote:

Tried again this morning, and first use of a hot tap results in hot
water arriving much quicker.

Is there a small hot-water leak somewhere? i.e. is hot water being
leaking at some place between the boiler and the tap? This would
dleave a shorter pipe run for the hot water to travel before reaching
the tap

That made me run upstairs to look! No, no leaks. All pipes neatly
capped and not leaking. There were no other changes to any pipes, other
than in the bathroom.
--
Graeme

On 28/04/2017 13:54, Graeme wrote:
In message ,
RobertL writes
On Friday, April 28, 2017 at 1:15:20 PM UTC+1, Graeme wrote:

Tried again this morning, and first use of a hot tap results in hot
water arriving much quicker.

Is there a small hot-water leak somewhere? i.e. is hot water being
leaking at some place between the boiler and the tap? This would
dleave a shorter pipe run for the hot water to travel before reaching
the tap

That made me run upstairs to look! No, no leaks. All pipes neatly
capped and not leaking. There were no other changes to any pipes, other
than in the bathroom.

I can think of a possible but highly unlikely explanation:
There are two possible routes through the pipework for the hot water to
reach your tap. The shorter route got air locked when they drained down
the system to cap off pipes in the bathroom. That left the water to find
its way round the longer route. The air lock sorted itself out
overnight, and now the water is taking the shorter route.

GB presented the following explanation :
I can think of a possible but highly unlikely explanation:
There are two possible routes through the pipework for the hot water to reach
your tap. The shorter route got air locked when they drained down the system
to cap off pipes in the bathroom. That left the water to find its way round
the longer route. The air lock sorted itself out overnight, and now the water
is taking the shorter route.

That is the only explanation I would agree with.

In message , GB
writes

I can think of a possible but highly unlikely explanation:
There are two possible routes through the pipework for the hot water to
reach your tap. The shorter route got air locked when they drained down
the system to cap off pipes in the bathroom. That left the water to
find its way round the longer route. The air lock sorted itself out
overnight, and now the water is taking the shorter route.

Brilliant. That sounds entirely plausible. Really. Tracing cables and
pipes in this house is a nightmare. It is quite a large house, built
1880, and, many years ago converted for guest house/B&B use with en
suite bathrooms. Then a small room on one side was extended to form a
Post Office and, at some point, central heating was added, but only
downstairs. We extended the CH 15 years ago. Oh, and a rewire probably
20 years ago. Add to that multiple telephone systems over the years
with two lines, extender bells and all sorts, and trying to find what
goes where is almost impossible. I could mention an alarm system and
dedicated wiring for the PO, and an extra bathroom built on one side of
the house. There are blanked off electrical fittings everywhere.

Getting back to the water, including what was the PO, there are nine
toilets, two baths (one of which was removed earlier this week), six
showers, ten hand basins, four sinks plus the usual supplies for washing
machines and dish washers, in two separate rooms. The chances of
someone, at some time, creating a loop in the hot water pipe run sounds
quite likely or, at least, not unlikely.

--
Graeme