Hot water taking ages to come through

[bloodoo]

Following major renovations it now takes ages for hot water to reach our upstairs bathrooms. I fully understand that this is due to a long line of hot water piping needing to be purged of cold water before the hot eventually comes through.
The hot water tank (on the first floor) is less than 20 feet from the bathrooms. I plan to take a junction from the existing hot water draw off by the tank then up into the attic where I plan to "T" into the existing upstairs hot water line supplying the bathrooms. I would then either cap the original supply line or fit gate valves so that I can revert if need be.
So, after leaving the tank the hot water draw off line would split in two providing an upstairs supply and a separate downstairs hot water supply.
I would be grateful if knowledgeable members could tell me whether this plan is feasible or advisable. If it works, I hope to get hot water upstairs pretty quickly without the expense of a recirculating hot water pump.

 

[Tea-Break]

Have you considered a secondary return and timed circulating pump?

 

[Chuck]

I would be grateful if knowledgeable members could tell me whether this plan is feasible or advisable. If it works, I hope to get hot water upstairs pretty quickly without the expense of a recirculating hot water pump.

If I've understood what you're proposing correctly, then you will be creating two or more dead-legs in your DHW system, which is not not permitted. You also need to be careful that your new pipework isn't prone to airlocks. If I've got the wrong end of the stick, please post a sketch of what you are planning.

 

[bloodoo]

Have you considered a secondary return and timed circulating pump?

Thanks for your reply Tea-break. That may be the way I will have to go, especially considering Chuck's comment below
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If I've understood what you're proposing correctly, then you will be creating two or more dead-legs in your DHW system, which is not not permitted. You also need to be careful that your new pipework isn't prone to airlocks. If I've got the wrong end of the stick, please post a sketch of what you are planning.

Thanks Chuck. It did cross my mind that there would be a "dead leg" with stagnant water lying in it. I have attempted to attach a drawing for clarity.

 

[Ric2013]

You need to work on the details - leaving dead sections of pipe isolated by zone valves is a silly idea - but the idea itself is a good one.

In my own house I had a similar problem, due to a legacy of previous owners' unskilled work and poor-quality modifications. I now have a 22mm pipe running only to the bath, with a separate 15mm pipe running to the basin and then on to the kitchen. While 15mm does slow the flow a very little, it has half the quantity of standing water to have to drain away, hence less time spent waiting. My pipework is entirely in the first floor void. Short runs, use of pulled bends rather than elbows, and deburring joints correctly helps a lot and my new bath run actually gives a better flow rate from the gravity pressure hot tap than from the mains pressure cold tap.

You can run through the loft if you do it right, but it may be a longer run. In practice, running gravity systems properly is a job for a skilled plumber who ought to know the tweaks that make excellent pipework rather than merely satisfactory pipework.

If you're up for some DIY, may I suggest, somewhat optimistically, that you find a local competent plumber who may be happy to spend an hour designing the system properly so it will definitely work, charge you for the advice, and then you won't need to waste time and money doing things that #might# work. Or we can advise you, to a point.

 

[bloodoo]

You need to work on the details - leaving dead sections of pipe isolated by zone valves is a silly idea - but the idea itself is a good one.

In my own house I had a similar problem, due to a legacy of previous owners' unskilled work and poor-quality modifications. I now have a 22mm pipe running only to the bath, with a separate 15mm pipe running to the basin and then on to the kitchen. While 15mm does slow the flow a very little, it has half the quantity of standing water to have to drain away, hence less time spent waiting. My pipework is entirely in the first floor void. Short runs, use of pulled bends rather than elbows, and deburring joints correctly helps a lot and my new bath run actually gives a better flow rate from the gravity pressure hot tap than from the mains pressure cold tap.

You can run through the loft if you do it right, but it may be a longer run. In practice, running gravity systems properly is a job for a skilled plumber who ought to know the tweaks that make excellent pipework rather than merely satisfactory pipework.

If you're up for some DIY, may I suggest, somewhat optimistically, that you find a local competent plumber who may be happy to spend an hour designing the system properly so it will definitely work, charge you for the advice, and then you won't need to waste time and money doing things that #might# work. Or we can advise you, to a point.

Thanks Ric. I did wonder about cutting and capping immediately after the kitchen sink then removing the length of pipe between there and the new bathroom junction in the attic. That way there would be no lengths of stagnant water in the pipework but maybe still air locks? I had plumber in early doors and his proposal was a recirculating pump; he made no mention of what I am now suggesting, but maybe that was because it isn't allowed or its impractical.

 

[Ric2013]

Thanks Ric. I did wonder about cutting and capping immediately after the kitchen sink then removing the length of pipe between there and the new bathroom junction in the attic. That way there would be no lengths of stagnant water in the pipework but maybe still air locks?

Your sketch and idea quoted seems fairly reasonable. Try to cut and cap as close to the new pipe as possible (no more than 1 pipe diameter deadleg), or disconnect the redundant section altogether. And lots of insulation: so-called Byelaw thickness as a minimum.

In terms of air, if the cylinder is mains pressure (unvented) which it looks to be from your diagram, while it would be a good idea to put a manual bleed valve at the highest point just to get things started, you probably don't need one.

I would advise you to come down from that horizontal existing pipe before going up into the loft so as to prevent parasitical circulation of the heated water and to prevent air settling out in the loft section.

Something like this:

Provided hot water issues from the furthest tap within 30 seconds, this kind of thing is fine. You'd use a recirculating pump when you can't achieve hot water in 30 seconds.

 

[Ben-gee]

When going from your new pipe in loft to the existing pipework, if you use an elbow rather than a tee there will be no dead leg at all....

 

[bloodoo]

Your sketch and idea quoted seems fairly reasonable. Try to cut and cap as close to the new pipe as possible (no more than 1 pipe diameter deadleg), or disconnect the redundant section altogether. And lots of insulation: so-called Byelaw thickness as a minimum.

In terms of air, if the cylinder is mains pressure (unvented) which it looks to be from your diagram, while it would be a good idea to put a manual bleed valve at the highest point just to get things started, you probably don't need one.

I would advise you to come down from that horizontal existing pipe before going up into the loft so as to prevent parasitical circulation of the heated water and to prevent air settling out in the loft section.

Something like this:

View attachment 46237

Provided hot water issues from the furthest tap within 30 seconds, this kind of thing is fine. You'd use a recirculating pump when you can't achieve hot water in 30 seconds.

Many thanks Ric, that all makes perfect sense.
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When going from your new pipe in loft to the existing pipework, if you use an elbow rather than a tee there will be no dead leg at all..

Thanks Ben-Gee. With the redundant section removed an elbow is the way to go