“After some investigation I found a faulty connection on the lighting circuit, a live cable was over tightened by someone, when I touched it this led to it breaking, so although it was working somewhat, when touch much power was being required by the double pump the supply could not cope.” – direct quote from my customer – Lee of Havant Hampshire.
Pulsing of pumps can be annoying but its often a very quick fix to sort things. As the inventor of the ShowerPowerBooster I was intrigued that the pumps only pulsed after a second pump was fitted and not when a single pump was first installed. This was something new.
Offering a free service visit to find out what was going on and curing the problem was worth a 420 mile round trip to check out why this happened. I think it was worth the trip because Lee and I went through the full arsenal of potential solutions and I will refer to each and every potential solution in this post. If you have a problem this post may give you an insight (if you have a problem), into why you may have a problem.
Lack of Water
If the pumps are being starved of water there is no possibility of them working properly.
Reasons For Lack of Water
Gate Valve Part Shut.
Gate Valve Part Blocked
Sediment in Cold Water Tank
Sediment in Hot Water Cylinder
Why Pumps Pulse When They Lack Water
When a pump pumps water there is a low tone as the pump pushes its maximum amount of water. If it runs out of water to pump the pump volute will have a mix of air and water and the pump rotor will spins rapidly and you will hear a higher pitch sound.
If you are restricting water to the pump the pump will take what water it can from the vent pipe until there is insufficient water and the pump ramps up and down. When the pump spins in an air/water mix it effectively stops pumping which means that whatever water is getting by a blocked valve refills the vent pipe until such time as the pump volute fills with water and the pump instead of spinning in air, the pump starts pumping water again.This cycle repeats and you will hear the pump ramping up and down continiously.
How do I check to see if this is my problem.
The sound from the pumps is a very good indicator but you can also check the flow with and without the pump running. A typical hot shower at 42 degrees centigrade is a mix of 4 litres of hot mixed with 2 litres of cold. If the maximum flow from the shower when turned to full hot is not increased when the shower head is removed then lack of water is very likely. Measure the flow with a measuring jug and let us know the results in litres per minute if you like.
If your pipes are laid in such a way they can trap air this air can move about and depending on where it lays in your pipes it can increase and decrease resistance. Lets assume the air sits near your pump to start with and the pump starts up. The water flow moves the air along the pipe to a high point and there it blocks the pipe and causes a severed restriction to flow. As the flow drops the pressure created by the pump increases to a point where it pushes the air beyond the restriction so the pipe flows freely again. Unfortunately as the flow increases the pressure created by the pump decreases, the flow rate decreases, the air is no longer pushed along and it returns to the high point where it blocks the pipe again. Repeat.
The obvious first step is to look for potential high points and a hot pipe which is connected near the cylinder, rises into the loft, runs across the loft, and falls to the shower is an obvious example of where this problem might be seen. Reconnecting the pipe which runs across the loft into the vent pipe in the loft will if this is the problem, greatly improve the effectiveness of the pump and stop pulsing.
For some installations the pipes are hidden under floorboards etc. With the shower head removed and the shower valve turned to full hot and the pump turned on, there is a good chance that you will flush the air out so doing this is one quick attempted fix that we always recommend (and in a large number of cases this is all you need do). If you have 15mm pipework you are often successful in flushing out air. If you have 22mm pipework for the same flow the speed of the water is less than half that of the same volume of water flowing through a 15mm pipe. As a result 22mm pipe can often cause more problems than 15mm pipe. For a bath a 22mm pipe is always recommended in order to get higher fill rates but for a shower the head loss in a 15mm pipe is minimal and the advantage of being better able to flush out air of greater advantage.
The shower head is the single biggest cause of back pressure and rightly so. It is the shower head which restricts the flow into multiple jets and accelerates streams of water. For a good shower you need multiple fine jets which gives you an optimal balance between the power of the shower stream and the volume of water to wash away suds. Too little water and it takes an age to wash away suds so you end up using more water. The flow is also critical to back pressure and if its back pressure from the shower head which is causing your pulsing then you can prove or disprove this by simply removing the shower head. The flow will increase and the back pressure from the shower head disappears. If the pulsing disappears when you remove the shower head this is a good indication that a better shower head could solve the problem. We suggest you purchase a WRightChoice Shower Head as these shower heads maximise performance and get the pressure/flow balance right.
In combination with your shower head the shower hose is very important and it is the internal bore of the shower hose which determines the back pressure. There are standard shower hoses which have 6mm and 8mm internal bores and shower hoses which have 10mm and 11mm internal bores resulting in low head loss. For a typical shower flow the head loss is very sensitive to the actual internal bore so whilst the head loss in a 8mm hose is very high the head loss in a 10mm hose is very low and the advantage of going from 10mm to 11mm very small. It is likely that a 11mm shower hose will not fit into a shower holder designed for a 8mm shower hose so we only sell a 10mm WRightChoice Shower Hose.
Temperature Of Water
In the case of my customer in Havant the thermostat on the hot water cylinder was faulty and although the thermostat was turned to 55 deg C the water was too hot to touch. This has two effects on the efficient operation of a ShowerPowerBooster. Whilst a typical hot shower at 42 deg C requires 2/3 hot and 1/3 cold, in the case where a hot water feed is 85 deg C the shower will require 2/3 cold to 1/3 hot. If you opted for a single pump on the hot only you will only benefit from a boost on 1/3 of the flow to the mixer plus the hot water may upset the Anti Scald feature on you shower mixer.
It could be that the high temperature of the hot is causing your mixer to ‘panic’ and over correct when it perceives scalding hot water. If could be that the mixer valve perceives scalding hot water when in reality it is not scalding hot water. If you shower mixers temperature control is over correcting, sticking, and/or faulty, this is something that can only be resolved by swapping over the mixer and this is often the last resort. Many plumbers will often have a spare mixer in the back of the van to do a quick swap just to diagnose the problem, but for DIY fitter, a visit to B&Q after reading my article on what is a good mixer is a good way forward.
Fault Power Supply (New)
My customer in Havant had scalding hot water due to a faulty thermostat on the hot water cylinder but this was not the reason for the pumps pulsing.
The shower head had a poor and inadequate spray pattern but this was not the reason for the pumps pulsing.
The shower hose was a 8mm standard hose resulting in high head loss.
A pressure test with the gage which I screwed into the shower head showed a .6 bar increase in pressure for each pump so the pumps were working well.
The flow tests proved it was not lack of water.
Lee had already changed the shower mixer.
The pumps only pulsed when both pumps were run together
Changing the transformer made no difference
Plugging in the original transformer into a downstairs 3 pin socket and running a 2 metre extension cable into the loft and the pumps stopped pulsing.
I left Lee to find the electrical fault and report back to me which he has done.
I suggest that if you experience a problem that you try running the pumps from a different socket just to check.