Shower: where to begin

Well its an option. Alternatively the venturi shower is designed for situations such as yours.

Have you measured the actual cold main pressure? It would help to work out how much boost or cut you need to get things closer to balanced.

Stuart turner to a do one of their entry level Showermate single sided pumps for around £130... that will do about 2.5 bar IIRC.

Not really ideal for the job... many of the entry level ones will have a maximum head of only 5m (so about 0.5 bar) where you could do with something closer to 3 probably. Also they lack a mechanism to detect the onset of flow and power up automatically, and shut off when flow ceases. Lastly they are not really designed for fresh water applications - especially if its a hard water area.

You could try that first - it might give you a cheap improvement.

Yup, there have been a few cases like that (hence my comment about my suspicion that there are more serious accidents with gravity hot water systems). Many of these seem to be caused by electrically heated cylinders boiling and overflowing into plastic cold cisterns that are not well enough supported.

If you are confident that you have enough hot delivery, just use a relatively cheap manual low pressure mixer taking the cold feed from your header tank. I was working to a tight budget when I put my current shower in many years ago and the ceramic mixer tap (probably Wickes, possibly Screwfix) is smooth, progressive, and very controllable. I don't have vulnerable users so don't see the need for thermostatic control or protection. I do have a double ended pump to get a decent pressure and flow rate, originally a cheap one until it leaked.

As an aside, I now mount my pumps in a small plastic header tank with a drain into the shower tray, having had two of them develop leaks.

Wimp, take a cold shower. Soap dissolves in cold water.

If its a vented cylinder then it must have a cold header tank. Run cold from that and use a shower pump.

Mike

wer than cold, ie vented cylinder versus mains. Any recommendations, sugges tions etc?

Am searching for venturi showers. Not seen anything suitable yet.

But this isn't quite adding up. Specs on the units I've seen say for

Have you checked it with the shower head removed? Is it a hard water area? Shower heads can restrict flow dramatically, especially if scaled a bit. The restriction will make the mixing at unbalanced pressures more "twitchy"

no... 3 floors is about 20-25' so 2/3 bar not 2 bar.

No I don't have a measuring wotsit. But at any given flow knob setting presumably a service valve could help equalise pressures more nearly.

I'm going to check it like that, I suspect that may be part of the problem. The shower mixer has endured 35 years or so of scaly water, though the head & hose are recent.

NT

Would the HW feed be better off with a single or double nonreturn valve? I presume the latter would have more impact on flow.

NT

The thermostatic control in our 22 year old Aqualisa has been changed twice despite being fed from the water softener.

Shower doctor dot com>>>>>>

With careful piping and a shower designed for low pressure operation,

Might be worth getting one, so you have a feel from the magnitude f the problem you are trying to solve. Probably only 10 to 15 quid from a plumber's merchant.

A service valve can throttle the maximum flow rate, but it won't reduce the pressure. So if you attempt to to mix with a low pressure DHW, and then apply enough flow resistance to the outlet of the mixer, you will still likely back feed the DHW.

You need a PRV. One like:

Might be handy since it shows you what output pressure you are getting.

You may find you need to specifically look for a head that is designed for low pressure operation.

Single would be better (double is only usually a requirement when protecting a public water supply from contamination).

However you may just find that the cold pressure forces it shut and you get no HW flow at all.

You don't need a pump with adequate sized pipework (with careful pipe runs) and a low pressure shower.

Why not just have a normal electric shower? Mains pressure, heated as you use it.

Today it got a new hose & head. The new head has way more holes than the ol d one, and the hose is 11mm not 5mm bore!. And there were what look like lu mps of rust partly blocking the 5mm, so no wonder it was misbehaving. Tomor row will give it a good test run & see how much better it is. I can see str aight away there's way more flow.

Next job is a PRV. The question is: honeywell £24 no gauge, another £6 with, or toolsatan £20 with gauge? Screwfix reviews for the no n-honeywell aren't too good, so I'm inclined to get the better one. Is it w orth adding a gauge?

FWIW I turned both sink taps on full. The last 5m or so to the sink is plum bed in 22mm hot, 15mm cold, before that it's all 22mm. The hot tap produces more flow at max than the cold.

NT