HW circulation

[Fred]

Hi,

I am interested in fitting a circulating pump to my HW. If I was plumbing the house from scratch, would I be best to run a ring of pipe and tee off short runs from the ring to each tap? The only disadvantage I can see with this arrangement is that there would be a couple of feet of cold water in the pipe work from the ring to the tap, though I'm not sure whether this would be a problem? The advantage is that no tap needs an individual return.

Unfortunately I do not have a house that I am plumbing from scratch so I need to retrofit. The problem with the existing plumbing is that it is not in a loop so would I need to tee off returns at every tap. Would you fit the returns as close to each tap as possible to minimise the cold water or would it be ok to have a couple of foot of cold water as described above?

Can the returns be joined wherever is convenient or is it best to bring them all together at one point? I'm thinking that I have read here about CH and that it is important to combine CH returns in one place to prevent reverse circulation. Is this a consideration with HW also?

Because each tap will have its own return does this mean that the returns would need throttling down, just as you would balance a CH system?

I did ask about this once before and it was suggested to use microbore for the returns but I have never seen insulation for microbore. Does it exist?

Do you have the pump at the front, pushing the water around or do you fit it at the end sucking it back or doesn't it matter?

At the moment my plumbing seems to run like this: cylinder to bath in

22mm with a reducing tee to a 15mm branch.

The 15mm branch is tee'd again: one short run to the right goes to the bathroom basin; the run to the left goes downstairs.

The downstairs presumably tee's to go to the cloakroom and washing machine in one direction and the kitchen sink in the other.

There is also a power shower tee'd off the bath supply. I am curious about this. The shower has its own cold feed from the tank, shouldn't it have its own hot feed too?

Can I pump this simply by teeing returns from each outlet or will some rearranging be required?

Will it cause problems having both shower pump and circulating pump on the same circuit? What if the shower sucks water faster than the circulating pump? Would that cause problems?

Thanks in advance.

[Ed Sirett]

You'd find the HW comes through so quickly you'd forget about even a few meters of "unpreheated" pipe.

You only need to add a pipe from the furthest away part of the HW pipework. Essentially, even making part of the DHW pipework on a loop will improve things so much that you need not worry about making things really complicated. In the worst case you have two DHW fee which both go off in opposite directions both for a long way. In which case you you might consider two secondary circuits each with their own pump. etc.etc. In your case something from down stairs will do the trick nicely.

Use what ever is easiest. Insulation is essential and plastic pipe has a head start in that regard.

Invariably the pump goes at the end and gently (setting 1) pulls the water round, the pump setting should be so gentle than negative pressures should not occur.

N.B. This pump will be a /bronze/ version of the domestic circulator cost

5x as much - or you will get rusty HW, and a failed pump, but not always.

Ideally, perhaps it should. The cold feed (may) also make sure the cold runs out last to prevent scalding.

just tee from the kitchen /or/ the cloakroom back to the bronze pump and then tee into the cold inlet supply pipe to the HW cylinder.

Set pump on minimum and also partially close the outlet isolator or add gate valve and nearly close than. You need just enough circulation to keep the DHW pipework pre heated, no more.

Just possibly, if the secondary loop is set up right then the chance of dragging cool/cold water backwards should be very small. A non return valve can help but be warned a NRV + pump can easily make a nuissance noise.

What if the shower sucks water faster than the

See above.

1) You want the pump on a timer and/or PIR so that it pre heats the pipes before you get up.

2) When you are working in the kitchen.

From your description I seriously don't think you have a house which is in the league for a secondary circulator.

The ones I have done have been for beds 6+ & baths 3+