Advice sought on impeller pump usage

[Noddy's Big Ears]

Hi all I have a particular problem with hot water in my house. The details are as follows:

1. Gravity fed system with cold water tank in loft with boiler and HW storage tank on 1st floor
2. Hot water supply on ground floor and 1st floor completely adequate.
3. Hot water supply in ensuite on 2nd floor sucks and completely stops when hot water being used on 1st or ground floors. My own investigations have revealed that:
4. The hot water supply to the second floor is via 15mm pipe whereas it is via 22mm pipe to the 1st and ground floors
5. The cold water supply to the 2nd and ground floors is directly from the mains and the supply to the 1st floor is from loft tank. In order to sort this out I have done a little research in this group and elsewhere. It seems that my best/cheapest/least disruptive options are:
6. Supply the 2nd floor HW via 22mm pipe. I don't really like the disruptiveness of this and am not convinced it would make much difference.

1. Install an impeller pump in the 2nd floor ensuite.

I particularly like option 2 but have the following queries which I hope someone here can help with. These are:

1. It looks like these are primarily designed for showers. Presumably, though, there is no reason why I couldn't fit one to feed the whole of the ensuite, ie, both the bath and the basin. If this is a problem I could consider just pumping the bath HW tap.
2. I have searched for a supplier and the cheapest I can find is the

1.5 bar SF Turbo 2 pump from Argos (catalogue 830/7554) at £99.99. However, this is a twin pump and I only need a single one. Can I use a twin pump to pump only one pipe? I can also get a 10% discount from Argos - hence the particular interest in this item.

1. Also would 1.5 bar be adequate for a decent enough pressure or should I try to get a meatier one from elsewhere? All helpful suggestions gratefully received.

[Paul Worsley]

What is happening is that when you use a tap downstairs, it is creating a vacuum in the supply pipe to the 2nd storey. This is due to not enough head of water supplying the cylinder.

You may find that the outlet in the top of the cylinder is constrained due to a build up of lime scale, you can check this by removing the pipe and looking into the fitting and pipe. Alternatively, the inlet to the tank is constrained due to the bottom of the cylinder being full of limescale, this is not so easy to check.

If you are in a hard water area, and the tank is more than 15 years old, the best thing might be to change it. If you do decide to change it, consider an unvented mains fed cylinder - this would solve all your problems.

A normal pump is not going to help as you need to have a flow to start with for the pump to cut in. You could use a negative head pump, but these cost a fortune.

Paul

[John]

SNIP

I interpreted the OPs system as having a loft higher than the 2nd floor taps. The problems arose when a downstairs tap is turned on and otherwise the 2nd floor taps delivered water at a low rate. Your interpretation may differ?

Agreed. Also worth considering is the size of the pipe from loft storage tank into the cylinder.

Possibly but they are not a panacea. Also as an unvented cylinder has the potential to explode if not installed correctly I would be wary of suggesting someone who has to ask the original question undertakes this sort of exercise

If there is a small flow then a negative head pump is not required. A standard one will suffice.

[Paul Worsley]

I agree that that from the information supliled, the loft is above the 2nd floor, otherwise they would have no water at all.

Upgrading to 28mm would be a good idea, but the problem most likly exists whithin the cylider.

Hopefully, the unvented cylinder would be installed by profesionals that have certification to do it (as they must)

They have no flow when the lower taps are in use.

Paul

[John]

Some time ago in this group there was mention that this "requirement" had been waived but don't take my word for it.

If the pump is located at the (shared) outlet to the cylinder then no matter where the flow sets off for there will be a flow to start the pump. Of course some restriction to other outlets may be necessary then.