Can I use a Twin impellar pump to boost hot pressure only..?

[Softus]

Can you point to where I have made an assumption that the OP has a cistern of sufficient capacity?

Certainly - here:

You would be better off changing the mains over to gravity as well and use the pump as per design.

You've decided that this solution is better, without knowing about the existing resources. I made no such assumption, and advised on the basis of what I knew from the information given by the OP.

YOU on the other hand advised the use of a prv without even asking if the OP has a cistern.

I don't quite see your point. Do you believe, for some reason, that adding a PRD would be harder and/or more expensive than providing a gravity cold service to the pump, even if there were an existing cistern of sufficient capacity?

Its important if you want to give the correct advise which you dont seem to be capable of doing.

OK, so you think it's important. If you feel that strongly about it then just ignore my opinions, but bear in mind that the OP is the one who needs convincing that you're right. Picking arguments with all and sundry is unlikely to achieve that.

 

[Water Systems]

Water Systems wrote

Run the hot through both side of the pump

Do you mean in series through the pump ie inlet -outlet -inlet- outlet and then the equalising valve. ??

No. Parallel. Keeps both sides wet. You could put in in series. But look at the pump and see what the inlet pressures should be. If one side raises it to 1.5 bar and this is fed into the other side, will he pump accept 1.5 bar? The makers bumph will state this. If it can then it may be worth it piping up in series not parallel. Then you may get ~3 bar out of it on the hot side. If this is more than the cold water mains pressure then the pressure equalisation valve will drop the hot to the cold water mains pressure and the maximum pressure will be achievable.

 

[Softus]

Talking of silly ideas, we now have our resident maestro performing...

Parallel. Keeps both sides wet.

If it can then it may be worth it piping up in series not parallel. Then you may get ~3 bar out of it on the hot side.

 

[MON5TER]

Thanks Watersystems.

Just to clarify are you siggesting:

Split the hot supply to 2 pipes. One to each side of the pump. Bring the output of the pump together into 1 pipe. Fit the hot and mains cold to the pressure equlalisation valve and then feed to the mixer tap....

FWIW I have a tank in the loft (not very big about 25 gallons) which supplies the calorifier which is on the ground floor.

I would prefer to avoid running a cold gravity supply to the bath as the pipe run will be difficult. I have T&G chipboard floors also, which are a pain....

Thanks for the suggestions so far.

 

[Bigburn]

MON5TER wrote

I would prefer to avoid running a cold gravity supply to the bath as the pipe run will be difficult.

Can never understand why people connect the cold bath supply from the mains when the hot is gravity.

 

[MON5TER]

MON5TER wrote

I would prefer to avoid running a cold gravity supply to the bath as the pipe run will be difficult.

Can never understand why people connect the cold bath supply from the mains when the hot is gravity.

Me neither! I assumed it would be gravity... Should have checked it first!

What do you think of the connecting in parallel idea?

 

[Bigburn]

Water Systems wrote

No. Parallel.

So you effectively doubling the flowrate on the outlet side where the pipes T together.
Wont the pumps cavitate like hell being fed from only one pipe on the inlet sides ??.

 

[MON5TER]

How about if I pass both hot and cold supplies through one of these and then through the pump?

http://www.plumbworld.co.uk/5-230

Or hot through the pump in parallel, then into the valve. Cold direct into the valve...

As you can see, I am out of my depth here and have a 38 weeks pregnant wife who wants the bathroom finishing!! We have another so its not too much of a problem.... bathroom that is not wife...

 

[Bigburn]

MON5TER wrote

What do you think of the connecting in parallel idea?

See my last post.
No doubt WS will have some cute answer up his sleeve.

 

[ChrisR]

How about if I pass both hot and cold supplies through one of these {PEV} and then through the pump?

Eeeek no the pump wouldn't like that.

 

[Water Systems]

How about if I pass both hot and cold supplies through one of these and then through the pump?

http://www.plumbworld.co.uk/5-230

Or hot through the pump in parallel, then into the valve. Cold direct into the valve...

As you can see, I am out of my depth here and have a 38 weeks pregnant wife who wants the bathroom finishing!! We have another so its not too much of a problem.... bathroom that is not wife...

No. After the pump. then to the mixer.

 

[Water Systems]

MOD 2 removed

use the edit key or the rest of your double posts go

edit this again PLEASE

 

[Water Systems]

Thanks Watersystems.

Just to clarify are you siggesting:

Split the hot supply to 2 pipes. One to each side of the pump. Bring the output of the pump together into 1 pipe. Fit the hot and mains cold to the pressure equlalisation valve and then feed to the mixer tap....

Yep. Just do as I say. Forget the other odd suggestions.

 

[MON5TER]

Thanks again. Think I'll give that a go.

Bigburn, what does cavitate mean??

 

[Softus]

Just do as I say. Forget the other odd suggestions.

Feeding hot to both sides of the pump wasn't your suggestion in the first place.